synthetic gear oil and balk ring synchromesh

[KobaltBlau]

Hello All, I am new here so hopefully I followed the protocol.

My question is regarding balk ring syncros, also called servo syncros, and their use with synthetic gear oil. Porsche originally invented this mechanism before the now common borg warner type was invented, and kept using it much later than other manufacturers until 1986.

Here is the best explanation I could find online about the way this type of mechanism works, scroll down to "SERVO SYNCHROS":

http://www.gordon-glasgow.org/RSR_4speed.asp

I have a better explanation in a book but it is copyrighted and I don't have a scanner to show the figure.

here's a moderately poor picture of the two synchromesh types, with the balk ring type on the right. you can see the stop that the split balk ring runs up against:

My particular application is using the Porsche 915 transaxle, but there are several other transmissions that use this synchromesh type, including older datsuns and older bmws.

here's a photo of the transaxle:

Consensus within the porsche community is that synthetics are "too slippery" for this balk ring synchromesh mechanism, particularly when warm. Several people have done back-to-back type tests, and experienced better performance with SWEPCO, a high quality "dino oil" than they did with the synthetic (primarily mobil 1 75w-90). Others have reported that regular valvoline dino gear oil works well, especially in 85w-140. Here are some quotes from very well respected people in the community:

Bill:

quote:

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The reason that Swepco works better than synthetic in the 915, is the design of the syncros. The Porsche style syncros used thru 86 in the 915 are a multipiece(7 parts/syncro) design which NEED friction to work. When synthetic is used the required friction is reduced leading to relativly poor shifting(grunching)and higher effort. The G50's used since 87 have a much simpler Borg Warner designed sycro(think Ford Mustang) which does respond well to synthetic.

also:

The slower and more deliberately one shifts with synthetic the less of an issue arises.

and:

tried M1 syntheic gear lube and at first was happy w/ the results, but w/ use became more and mor disatisfied. You will find w/ time and use that the synrcos work less and less efficiently and you will have to shift slower and slower for them to work effectively. My theory is that the remanats of the old fluids additive package remain but are gradually worn away. I do not speed shift as a rule but there are times when you will want to hurry a shift a bit and you will be very very sorry w/ what happens at that time.

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It's important to note that Bill's transmission has a loop cooler on it which makes it impossible to change all of the fluid. perhaps 1/3 or 1/2 qt of the old SWEPCO probably remained in his trans.

Hayden:

quote:

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I have only performed one deliberate test on a synchro box. In one of my own cars (with transmission in un-inspected condition at this point). I drove for a couple of months with shift linkage, clutch and oil level all correct, using the oil that was in the car when I bought it. I then systematically tested Mobil 1, Castrol Syntec and Swepco 201.

The Mobil 1 and Castrol both felt better than the unknown oil that was in the trans - but only when cold. As they warmed up, the synchonizer action became weaker and the transmission required a more deliberate shift, with lower cadence.
The Swepco 201 felt like crap when the transmission was cold, heavy, baulky, equally as distracting (in a different manner) as the synths when they were warm.
However, when the 201 was warm, it felt great, light and with consistent synchro action, better than the original unknown oil and equally as light as the synths when they were cold.

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Steve:

quote:

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All Porsche transmissions use a very steep hypoid angle in the differential due to the necessity of close shaft spacing. This is a very highly stressed item and requires the use of a GL-5 Specification gear Lube. Since these gearboxes all use the Porsche-design balk ring syncromesh, they depend upon some friction for these brake-band type syncro's to work properly. The best gear lube for a 901-915-930 transmission is the superb Swepco 201 gear oil. Using a synthetic gear oil in these transmissions will result in higher syncro wear and stiffer shift quality.

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I use the transmission oil at both very low and very high temperatures, so the low pour point and good protection of a synthetic is desirable. However, I want my synchros to work well. Many of these transaxles also have a ZF multiplate clutch friction limited slip, including mine.

Also, Swepco makes an 80w-90 (201/203) and an 80w-140 (210/212). They don't publish pour points, but would the pour point for an 80w-90 probably be lower? I'd like the extra protection of the 80w-140 at the race track (although I guess it will run hotter), but I'd like some cold weather performance too. This is why the synthetic looks good, but there is the synchromesh issue.

Any thoughts? Thanks in advance!!

Andy

 

[cryptokid]

thats the 911 trans right?

i have also heard to use nothing but swepco in porsche 915 or 905 transmissions.

 

[KobaltBlau]

cryptokid, there are 3 major transmissons in air cooled 6 cylinder porsches. the 901, 915, 930, and G50. The 901, 915, and 930 are all porsche designed and built and use the balk ring synchros as described above. The G50 is a getrag trans and uses modern borg warner type synchros. My post refers to the 915 specifically but the synchro compatibility with slick oils applies to any balk ring synchro transmission including some in austin-healeys, datsuns, bmws, and probably several others.

 

[KobaltBlau]

er, that would be 4 transmissions.

 

[cryptokid]

ah yeah i was thinking of the 901, not the non existant 905.

 

[tdi-rick]

could always get it converted to a dog box, then you could run something like NEO 75w-90 RHD.

Seriously though, I have no idea if this available in the US, or even what its retail name would be, but Castrol Australia have a full synthetic 75w-90 GL-5 hypoid/LSD manual trans fluid called Syntrax that has very good synchro performance.
It is a European (German ?) brew, and is recommended by Castrol in Oz for high performance/race use in Porsche and Ferrari transaxles. (as well as more pedestrian vehicles, and the drive axles of interstate semi's)

I've noticed that Castrol UK also have a Syntrax, but it isn't the same stuff, as the UK one is a semi-synth GL-4 75w-90.

Rick.

 

[KobaltBlau]

Interesting, Rick, thanks. Do you know if this is used successfully in the pre-87 porsche tranaxles? The earlier and later ones have different requirements due to their synchro design.

Good point on the dog box

most of those use straight cut gears which I'm not sure are ideal for street use...

 

[tdi-rick]

...well, it's recommended for them by Castrol Oz, but how it works...

If I was still around the race tracks I'd ask for you. Actually, a mate of mine race engineers a current GT3(?), but that doesn't really help you a lot either.

I have to talk to the Castrol tech guys next week re some TDS's, so I'll see if they have an internal/universal product code for it.
It does make it hard when they use different product names in different markets.

I have used it, and backed to backed it with Redline MT 90 in a straight gearbox application, and there was very little difference in synchro performance, just a slight edge to the MT 90, but again, they would be conventional synchros.

I was only joshing re the dog box 'cause yeah, most use straight cut gears which wail like banshees.
You never really notice it on the track, but I don't think you'd survive five minutes on the street.

Rick.

 

[KobaltBlau]

Thanks again, Rick.

I guess my primary focus here (maybe my post was too long) is: What factors can make synthetic gear oils work best with synchromesh that needs more friction than usual?

Perhaps since one of the experts I quoted experienced good performance only when cold with Mobil 1 75W90, a 75W140 would work better? Or is this mainly an additive issue?

Thanks again,

Andy

 

[tdi-rick]

I hope one of the experts on here can chime in as I'm a mechanic, not a lube engineer or triboligist.

My understanding is that an LSD fluid just plain wont work with synchros as we have two conflicting aims,
1. with an LSD a friction modifier is used to make the fluid 'more slippery' to limit 'chatter' of the clutch plates during use,
2. with synchros, you want the co-efficient of friction to increase, particularly as the clutch hubs are at the point of the dogs just engaging, so as to exactly match dog speeds.

I think this is where Redline have garnered their reputation with MTL and MT 90. Unfortunately they aren't any good to you.

I pinched this from the Redline site, it explains it better than I ever could;

quote:

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Red Line MTL and MT-90 are able to improve shifting in most manual transmissions and transaxles. They provide a relatively constant viscosity as temperature changes and provides the proper coefficient of friction to allow synchronizer engagement. Most gear oils are very viscous at lower temperatures. This higher viscosity requires increased shift effort to move the synchronizer gears with the shift fork and to squeeze the oil from between the synchronizer cone and the mating surface attached to the gear. Without


contact of these two surfaces, the gear speeds will not be synchronized and locking of the synchromesh gears will not occur. Excessive viscosity results in a longer time required to synchronize before locking occurs.

Viscosity of common lubricants at 0°C (32°F) is compared with Red Line MTL in the chart below. Note that the viscosity of ATF and 10W30 motor oil seems to be adequate. These lubricants are not well suited for transmission use because of two factors - shear stability and improper coefficient of friction - which will be discussed in more detail later. At even lower temperatures such as -17.7°C (0°F), the differences between conventional lubricants and Red Line MTL are even more dramatic. At such a temperature many of these lubricants would prevent shifting into certain gears, depending on the design of the transmission.

All oils are slippery, and with most lubricated components, the slipperier the better, but this is not so with manual transmissions. The synchronization of shifting gears requires friction to transfer energy from the synchronizer, which is locked to the input shaft, to its mating surface attached to the gear to be locked in as the drive gear. Few modern transmissions use sliding gears to change gearing other than for reverse gearing. Synchromesh transmissions have the gear pairs constantly in mesh. The drive gear is selected by using the shift forks to slide a synchronizer ring, which rotates at the same speed as the input shaft, in contact with the selected drive gear. Once the drive gear is brought to the same speed as the input shaft, the locking ring on the synchro assembly is allowed to slide over and lock into the drive gear.

The time this process takes depends on how easily the synchro ring moves and the rate of frictional energy transfer between the two synchronizer surfaces. Higher viscosity lubricants slow the sliding of the synchro ring on the input shaft and require a longer time for the oil to be squeezed out from between the mating synchronizer surfaces. After the lubricant is squeezed out, the coefficient of friction of the lubricant determines the rate of frictional energy transfer between the two surfaces. Slippery lubricants such as hypoid gear oils and ATFs can take too long to synchronize the gears, which promotes synchronizer wear. Red Line MTL and MT-90 has a coefficient of friction which is greater than conventional oils, allowing a quicker transfer of frictional energy. The graph below shows the desirable friction curve demonstrated by Red Line MTL compared to conventional lubricants.


Note how the coefficient of friction is greater for the MTL than all others except the motor oil. Some motor oils have an adequate dynamic coefficient of friction, but most have problems with the static and low velocity coefficient of friction which can result in clashing.

Clashing of the gears (actually clashing of the synchromesh gears, since the drive gears are always in contact) can occur if excessive shift effort is used in order to shift the locking ring into place before the surfaces have achieved equal speed. It may also occur at the end of a reasonably smooth shift if an instability exists in the coefficient of friction, causing stick-slip to occur. In this form of clashing, the ring slides on the mating synchro gear, but a sudden slippage causes a grinding of the gears. In order to prevent stick-slip from occuring and the gear clashing which results, the coefficient of friction should inflect downward as the relative speed drops to zero.

GEAR AND SYNCHRONIZER WEAR PROTECTION
Most manufacturers of manual transmissions and transaxles recommend an 80W or 90W GL-4 lubricant. GL-5 gears oils which are required in hypoid differentials are not used in most synchromesh transmissions because the chemicals used to provide the extreme pressure protection can be corrosive to synchronizers, which are commonly made of brass or bronze. Typically, the use of a GL-5 lubricant in a synchromesh transmission will shorten the synchronizer life by one half. The extreme pressure requirements of spur gears and helical gears found in transmissions are not nearly as great as found in rear-wheel drive differentials. A GL-4 lubricant provides adequate protection for most manual transmissions, unless a unique design consideration requires the extra protection of a GL-5.

The reason that many manufacturers have made recommendations of motor oils or ATFs is that petroleum 80W gear oils frequently do not shift well at low temperatures. Motor oils and ATFs are much more fluid


at lower temperatures and they are not corrosive toward synchros, but they provide very poor gear protection. These lubricants provide almost no extreme-pressure protection. In addition, multigrade motor oils and ATFs have very poor shear stability. The shearing action by a manual transmission on thickeners is much worse than in an engine or automatic transmission. Within 5,000 miles the thickeners can be rendered ineffective and the transmission will be operating on a much reduced level of protection, as shown in the graph below. In hot weather these transmissions will whine and rattle because of poor vibration dampening and metal contact. Red Line MTL and MT-90 provide the excellent gear protection of a GL-4 gear oil in a synthetic lubricant which spans hot and cold temperatures and will not shear or oxidize with use.

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Actually, if you've stuck this far, Redline recommend 75w-90NS or 75w-140NS for GL 5 applications. Might be worth a shot ? although I have no idea how they'd work with a LSD.

Rick.

 

[KobaltBlau]

quote:

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Originally posted by tdi-rick:
My understanding is that an LSD fluid just plain wont work with synchros as we have two conflicting aims,
1. with an LSD a friction modifier is used to make the fluid 'more slippery' to limit 'chatter' of the clutch plates during use,
2. with synchros, you want the co-efficient of friction to increase, particularly as the clutch hubs are at the point of the dogs just engaging, so as to exactly match dog speeds.

---

Yes Rick, add to this the ring & pinon in there (needs GL-5 as you noted) and the bearings (slicker is better) and you have a whole pile of conflicting requirements in a transaxle like this. HOWEVER, people have had good success with the SWEPCO 201, 212, and basic valvoline dino gear oil, including 85w-140 and I think 80w-90.

75w-90ns or 75w-140ns would indeed be the redline fluids to use, if there wasn't a friction (multi clutch plate) LSD. One guy used 75w-90ns in his 915 and had problems with LSD chatter. Redline wouldn't be suprised about this since it doesn't have a friction modifier. Another guy uses the 75w-90ns with 10% by volume Dow Corning Molykote 'M' moly gear oil additive. This moly additive keeps his LSD from chattering. However, I don't think he has used (abused) his trans on the track.

plus, I really didn't like this quote from another very reputable porsche guy. the 901 is a little different transmission but the synchros and ZF limited slip unit are the same design:

brad:

quote:

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My 901 ZF LSDs wear out 2 times faster with Redline in them (race cars) and we are sponsored by Redline with full engineering support. The boxes themselves wear out the sliders and synchro rings almost twice as fast as the box we use SWEPCO in.

The Porsche tranny engineers didnt have synthetics in their arsenal of engineering secrets back in 196X when they developed the 901 box. They specifically factored in the gear lube to help slow down the synchro's during engagement. Synthetic lubes dont help the pieces slow down and cause premature wear. The car will shift like gang busters for the first 800 miles or so.. then go down hill from there (over time)

I would imagine Bruce Anderson is one of only a hand full of people who has raced a 901 box at the 24 hour of Daytona (which is where you learn quickly what works and what doesnt).

---

Regading Bruce Anderson, he is a porsche racer type who noticed that SWEPCO increased the life of the ring & pinions in the 935 race cars from 40 hours to a whole season of endurance racing, supposedly.

It really seems like dino is just the way to go with these trannys. If there were lots of cars out there with this type of synchromesh, there would probably be a suitable synthetic fluid. I guess you can run a thinner dino if cold temperature use is an issue, but you have to have a thicker dino before you go to the track (high fluid temps).

The WRX guys seem to have similar problems. They have their front diff (and xfer case, I think) in unit with their trans, so they need a GL-5 for the hypoid gear set. On the other hand, their syncros, although they are the borg warner design (98% sure), are fairly finicky and need good friction. These guys have tried everything under the sun and seem to have the best performance with a good quality dino 75w-90 GL5. some of them do OK with redline 75w-90ns (some crunching), but they don't have a friction plate LSD so they don't have to add any friction modifer at all on top of the base ns stuff.

does an 80w-140 protect wear parts better than an 80w-90 at 212 degrees F, all else equal?

How about some suggestions for Dino gear oils with very high quality additive packages? SWEPCO is one of them but it's $50/gallon so there ought to be some other good stuff out there for that!

Synthetic blends are interesting as well, any thoughts on that? They bring the pour point down nicely, but I'm not sure if they would be "too slick" for the synchros like the full synths are.

Experts/Moderators/Sponsors, please feel free to weigh in!

Thanks Again!

 

[KobaltBlau]

I'm leaning toward using "Pennzoil® Gearplus® SAE 80W-140 GL-5" because it seems to be the only 80W-140 dino that ought to be widely available (is this true?). SWEPCO 210 and 212 are also 80W-140.

Does anyone know who retails Pennzoil Gear oil? I'm having trouble finding it.

Still hoping for some answers to the 3 bold questions at the bottom of my previous post...

Thanks, All!

 

[tdi-rick]

Further to what Molakule has suggested, I organised some NEO (I was sponsored at the time) for a mate of mine (a race car engineer). This was about 10 years ago for his girlfriends Peugeot 405 MI (transaxle, hypoid diff).
With the factory fluid they were having gear change problems when cold (only 10*C !)
With the NEO 75w-90, the gearbox shifted fine.
He was pretty impressed.
Admittedly, not a baulk ring synchro, but thinking back it was pretty impressive for an LSD fluid that was really designed around 'dog boxes.

Rick

 

[MolaKule]

quote:

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HOWEVER, people have had good success with the SWEPCO 201, 212, and basic valvoline dino gear oil, including 85w-140 and I think 80w-90.

---

I suspect this type of synchornizer is happy with synthetics, since it shares the same oil with an LSD system.

I would try a GL2-5 rated synthetic first in the 75W90 viscosity. I can't see where a 80W140 would produce anything but extremely rough shifts, unless this in one loose-goose tranny.

 

[edhackett]

KobaltBlau,

I never did find a gear oil that worked in my WRX. It went into the shop for a full sycnro replacement this morning. The problem is that a change in supplier resulted in syncros that were of a different material and out of spec dimension wise. Four to five thousand cars were affected. They have gone back to their original supplier.

Now, i do have an answer for you. I've owned more than a handful of Alfa Romeos from 1959 to 1982 models. They all used the Porsche style sycnros, and did not shift well with GL5 lubes.

Chevron Delo 80W-90 works like a charm in this type of transmission/transaxle. It does not contain sulfur/phosphorus EP additives, so does not attack the soft syncro material. It is GL5 rated for a transaxle, works perfectly with limited slip, and yet works fine in transmissions specifying a GL1 gear lube (1959 Alfa). That is assuming that the transmission is in proper working order. No oil will make worn syncros function properly.

The Delo gear lube will give you all the protection of a synthetic, but not the ease of shifting when cold. The 80W-90 is all you need for a transmission.

http://www.chevrontexacodelo.com/en/products/transmissionfluidgearoil/default.asp#

Ed

[ August 17, 2004, 01:32 AM: Message edited by: edhackett ]

 

[KobaltBlau]

quote:

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Originally posted by edhackett:
KobaltBlau,
I never did find a gear oil that worked in my WRX. It went into the shop for a full sycnro replacement this morning. The problem is that a change in supplier resulted in syncros that were of a different material and out of spec dimension wise. Four to five thousand cars were affected. They have gone back to their original supplier.

---

I'm sorry to hear that. What a pain!

quote:

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Originally posted by edhackett:
Now, i do have an answer for you. I've owned more than a handful of Alfa Romeos from 1959 to 1982 models. They all used the Porsche style sycnros, and did not shift well with GL5 lubes.

Chevron Delo 80W-90 works like a charm in this type of transmission/transaxle. It does not contain sulfur/phosphorus EP additives, so does not attack the soft syncro material. It is GL5 rated for a transaxle, works perfectly with limited slip, and yet works fine in transmissions specifying a GL1 gear lube (1959 Alfa). That is assuming that the transmission is in proper working order. No oil will make worn syncros function properly.

The Delo gear lube will give you all the protection of a synthetic, but not the ease of shifting when cold. The 80W-90 is all you need for a transmission.

---

Thank you, Ed. However, I didn't think the Delo was suitable for refill of limited slips. It says on their site it's suitable for "top-off" of limited slips but other gear lubes say they are suitable for "refill" of limited slips, and Delo doesn't, at least where I looked. I assume this meant it would need an additional LSD additive. Can someone set me straight on this? TIA!

quote:

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Originally posted by MolaKule:

I would try a GL2-5 rated synthetic first in the 75W90 viscosity. I can't see where a 80W140 would produce anything but extremely rough shifts, unless this in one loose-goose tranny.

---

okay MolaKule, let's forget the 80W-140

. Some others have used this, but they probably have old transmissions and/or are in hot temperatures. Mine is pretty fresh.

A few people have had bad results with regular OTC small container Mobil 1 75W-90 (contains friction modifier), slow shifting and grinding. Perhaps this is the combination of the friction modifier and the synthetic. I would be wary of using a synthetic that already has a friction modifier in it due to others' results. However, something like the redline 75w-90ns or the Mobil 1 SHC 75w-90 with a careful dose of friction modifier might work well. As I mentioned above, one guy adds 10% Dow Corning Molykote M to 75w-90ns redline and doesn't have LSD chatter. A single quart of Molykote M is $40 though!

quote:

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Originally posted by MolaKule:

I suspect this type of synchornizer is happy with synthetics, since it shares the same oil with an LSD system.

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Can you elaborate on this, MolaKule? I'm not sure I understand.

Thanks everyone, this is getting interesting

 

[KobaltBlau]

couple of other things:

here's a post where widman says Delo gear oil doesn't have a limited slip additive. I'm not saying this is true, but I think it's where I got the idea (plus the top-off/refill issue mentioned above)

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=16;t=000895;p=1#000001

still, maybe someone can confirm?

second, there are no soft metals or brass etc in this trans. all steel and iron. so synchros will not get eaten.

when I said above that the problem might be the combination of synthetics and a friction modifier, this is just a guess. People have had the most trouble with this combination. Dino with a friction modifier is no problem, even dino with moly. I looked around a little and people don't recommend moly in transmissions here (mostly), but I think it's fine in these trannys because of the metals used.

 

[tdi-rick]

KobaltBlau,
is the synchro baulk/crash issue on the up change, down change, or both ?

 

[KobaltBlau]

I don't think any of the people who tried full synthetics with LSD additives specified. My guess is they would have said something if it was just one direction, but I can't say for sure.

 

[edhackett]

Delo gear lube does contain a limited slip additive. Go to the link in my previous post and pull up the data sheet for the gear lube (left hand side of page, select region, product data, and pull up the PDF of the full specs for the oil.

Ed