I'm planning on replacing the diff fluid in my '02 Ranger 2WD which is limited-slip. I've considered Mobil 1, but I'm leaning toward Pennzoil 80W90 GL-5. Pennzoil's specs for this oil say it has the friction modifier "for limited-slip differentials". Should I still add a friction modifier Ford recommends?
Add friction modifier for limited-slip?
- Thread starter Woody
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I would be interested in that answer, too.
I just had my tranny fluid in my '95 Silverado changed to Mobil1. On its website it says it has a friction modifier included and that additional friction modifier was not needed for limited-slip differentials. However, my transmission man at a local reputable independent shop said that while the M1 fluid would work without it, adding a friction modifier was a good idea and strongly recommended.
Swapped out both my Dakota's differentials with M1 75w-90. The Dodge dealer here said that I MUST use the appropriate friction modifier for the limited slip rear end. So I did. Stuff's not cheap, either.
John.
John.
I ended up adding 2 bottles when I changed to Amsoil on the F150. One bottle still produced noise. These were the Ford bottles from the dealership.
JHZR2
Staff member
The only way to know is to figure out if you get clutch chatter going around corners when the diff is full hot.
Using some additive is a good idea in even non-lsd diffs, it sptabilizes metal surfaces, reducing wear.
JMH
Using some additive is a good idea in even non-lsd diffs, it sptabilizes metal surfaces, reducing wear.
JMH
Some of the synthetic gear lubes have the LS friction modifier built in. Redline and Royal Purple for example. I have posi on my Camaro and I'm using them with no extra modifier added. No chatter on turns.
The problem with too much added modifier is you may make it too slippery and lose your posi action altogether or diminish it to some degree.
What I would do is use a synth lube with built in modifier, and with no additional modifier added, then go out and try it. Drive some figure 8 circles in a parking lot and see if you get chatter. If you don't get chatter, you're done. If you do get chatter, go back and add a tube of modifier and try it again. Only use as much modifier as necessary to stop the chatter, and no more.
The problem with too much added modifier is you may make it too slippery and lose your posi action altogether or diminish it to some degree.
What I would do is use a synth lube with built in modifier, and with no additional modifier added, then go out and try it. Drive some figure 8 circles in a parking lot and see if you get chatter. If you don't get chatter, you're done. If you do get chatter, go back and add a tube of modifier and try it again. Only use as much modifier as necessary to stop the chatter, and no more.
Thanks for all the replies.
I'm not convinced to use synthetic gear lube yet because of the mixed reviews I've read. Can anyone give me some hard facts? I'm assuming the additive can be added to synthetic gear lube? BTW, does anyone have a favorite brand of additive?
MolaKule
Staff member
Woody,
If you order a gallon or more of our synthetic gear lubes (HDS-5), we provide (for free) a four ounce bottle of our LS additive if your duffy still chatters.
If you order a gallon or more of our synthetic gear lubes (HDS-5), we provide (for free) a four ounce bottle of our LS additive if your duffy still chatters.
That's a drag... Ford friction modifier is about $5 at the dealer.
A lot of the GL-5's out there have some friction modifiers in them for the LSD applications. I have one that I've used since new in my 1995 4Runner. 300,000 km and no noise, even on tight U-turns. But in my 99 4Runner I have to add the additive or it self destructs on U-turns. Nissans in general all need the additional.
Since there are no synthetic gear oils here and there are a few Expeditions (looking for synthetic 80W-140 LSD, I've been filling them with Delo Gear 85W-140 and adding the additive.
Since there are no synthetic gear oils here and there are a few Expeditions (looking for synthetic 80W-140 LSD, I've been filling them with Delo Gear 85W-140 and adding the additive.
When I was looking for a synthetic gear oil for my Torsen T2, I was only able to find 2 that did not have FM.
Redline 75W90NS
Neo 75W90 EP
MolaKule, are you saying your gear oil has no FM?
Redline 75W90NS
Neo 75W90 EP
MolaKule, are you saying your gear oil has no FM?
Replaced mine about a month ago in my 2000 f150 5.4L with the 3.55LS rearend. I used Redline 75-140 without any friction modifier. No new sounds from what was in it before -which is none. Locks up as expected if not better than was in it before. I'd try it without it as long as what your putting in it has it. Because i've heard if you get to much it could lock up all the time.
MolaKule
Staff member
NO. Our wesite says all our gear oils have FM's in them, which is why I said if you need more, we will send a 4 oz. bottle. We incude enough FM in the standard formulation for the "average" LSD owner.
We can provde a non-FM oil at your request and at no extra charge. We "aim" to please.
FWIW I changed the oil in the wife's limited slip 2003 Durango using 2 quarts of Valvoline (NAPA) 80W-90 dino lube and one 7oz. bottle of Trans-X additive. No chatter or other noise.
Friction modifier additives don't stabilize anything, they're there to reduce friction so your clutches do not chatter when rubbing against the steel discs.
I used Redline 75W-90 w/ the FM (not the NS) with my trueTrac/Torsen. I see zero reason to avoid gear oils that contain friction modifiers. They can't harm anything in open differentials or mechanical differentials. Eventually the FM's break-down but there's no additional harm.
On a clutch LSD, too much FM causes excessive slip and eventually inefficient torque biasing when you need the axles to lock up.
I just did a new Traction-Lok rebuild and used 2.5 qt of dino 85W-140 that contained friction modifier. I never added any extra Ford FM. I drove it for about 3-4 days and all of the loud noises went away. I can occaisonally hear it groan in a left turn, but overall I did not add any extra FM. The noise doesn't bother me, so why reduce the friction even more? I went with the T-lok rebuild project rather than fix the TrueTrac because I need good take-off traction in snow when winter comes by. An open differential + snow tires may just get you by, but I demand max traction. The TrueTrac wasn't half bad until I noticed abnormal torque biasing (ended up being 3 broken Grade 8 bolts).
I used Redline 75W-90 w/ the FM (not the NS) with my trueTrac/Torsen. I see zero reason to avoid gear oils that contain friction modifiers. They can't harm anything in open differentials or mechanical differentials. Eventually the FM's break-down but there's no additional harm.
On a clutch LSD, too much FM causes excessive slip and eventually inefficient torque biasing when you need the axles to lock up.
I just did a new Traction-Lok rebuild and used 2.5 qt of dino 85W-140 that contained friction modifier. I never added any extra Ford FM. I drove it for about 3-4 days and all of the loud noises went away. I can occaisonally hear it groan in a left turn, but overall I did not add any extra FM. The noise doesn't bother me, so why reduce the friction even more? I went with the T-lok rebuild project rather than fix the TrueTrac because I need good take-off traction in snow when winter comes by. An open differential + snow tires may just get you by, but I demand max traction. The TrueTrac wasn't half bad until I noticed abnormal torque biasing (ended up being 3 broken Grade 8 bolts).
For a Torsen, the addition of FM reduces the bias by about .2 or 10% for a T2 This is the same effect as going from a 90 weight oil to a 140 weight. Because of this, I choose to use non-FM oils in my Torsen, such as Redline 75W90NS, Neo 75W90 EP, and, for the next run, MolaKule's non-FM, by request, gear oil.
That's interesting to note! I never had a problem with torque biasing. In fact, up to the point where I removed the TrueTrac, I started to notice excessive torque biasing where the axles wouldn't rotate at different speeds when entering turns. At one point the car kept going straight on snow when my steering wheel was fully turned to the right.
I guess it's not a real problem for folks in Texas. In MI, I face snow, ice, slush, rain, and dry pavement... sometimes even as late as May.
10% is not that big of a deal, but I AutoX the car, and every advantage I can get...
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