Switching to Synthetic

[TLAR640]

I switched my '97 Silverado to M1 75w90 in the diff. and after 10k mi both axles & pinion seal developed leaks. However, my previous Silverado had axle seals replaced 2x over 150k when using only dino gear lube. Not sure if synthetic caused these leaks.

No further leaks in the 16k since replaced. The good news is they are not difficult/expensive to replace.

 

[Oldswagon]

I have decided that I am going to switch my car over to synthetic gear lube sometime before the fall. Before I do, I have a couple of questions.

Has anyone experienced seal leakage after switching to synthetic? Currently my axle and pinion seals do not leak. I have changed the rear end lube at least every 20K miles since I have owned the car, so the rear diff is very clean.

Does anyone have any recommendations for a good synthetic gear lube? I would prefer an OTC oil. It will be used in a fullsize RWD GM car with a 8.5" 10 bolt rear. The car sees some light towing over longer distances.

 

[Oldswagon]

Thanks for the reply. Since your Silverado probably had a 8.5" rear end too, this is a helpful response. When I worked at a local GM dealer we used to do a lot of axle seals on GM trucks, mostly 8.5" rears. It is an easy job, but if the oil leak goes unnoticed and it soaks the brake shoes in oil it can be an expensive repair (especially if the vehicle has new shoes). This is what I want to prevent on my car.

I am leaning toward Mobil 1, but I am unsure of the availability locally. Are any of the other OTC brands any good? I know I have seen Castrol, and I could probably get Pennzoil from the local dealer. Canadian Tire carries Red Line products now, and I know they make an excellent gear lube. However, I don't know if they sell any gear lube there (I have just notice motor oil and WW). Besides that, I bet the Redline would be double the price of Mobil 1.

Is there any type of gear lube that has a chemistry that is less likely to leak? PAO motor oils cause seal shrinkage while Ester motor oils cause seal swelling. Are their similar effects in gear lube base oils? If so, what type do each brand use?

Any other experiences with Synthetic gear lube is appreciated.

 

[Dick in Falls Church]

>>>I am leaning toward Mobil 1, but I am unsure of the availability locally. Are any of the other OTC brands any good?

If there is a Canadian Tire store near you, then you can probably call AMSOIL an OTC brand. It works.

 

[TheJMan19]

I changed my 1993 Explorer to M1 75W-90 about 7,000 miles ago. Works great except that I have a LSD and I still had to add friction modifier even though the bottle says that no friction modifier is needed. I changed the gear lube at 80,000 and it now was 87,600 miles on it.

No leaks as of yet.

 

[Oldswagon]

Thanks for the responses. My car does not have a LSD so I don't have to worry about any additives.

I went to Wal-Mart and Canadian Tire today to check out the selection in gear oils. Needless to say I was very disappointed. Canadian tire had Red Line products, but no gear oil. There was also plenty of Amsoil oils, even Motorcycle oil, but no gear oil. In fact, the only synthetic gear lube was the Motomaster brand, which is most likely made by Shell. Wal-mart only had Castrol synthetic gear lube.

I should be able to get Pennzoil synthetic gear lube from the Pennzoil dealer, but I will do some more shopping around. I am disappointed that I can't find any Mobil 1.

Any other comments or advice is appreciated.

 

[RavenTai]

is the pennsoil or castrol "synthetic" really synthetic? most store bought "synthetic" engine oil are group III, I wonder if the same aplies to gear oil?

 

[TallPaul]

quote:

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Originally posted by RavenTai:
...most store bought "synthetic" engine oil are group III, I wonder if the same aplies to gear oil?

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Bet it does. I just put Redline 75w90 in the rear end of my motorhome. That is a real synthetic.

[ July 10, 2004, 11:48 PM: Message edited by: TallPaul ]

 

[VaderSS]

While looking for a high grade gear oil that was not Group IV/V, I found that all synthetic gear oil(for major companies which is who I contacted) were actually IV/V. That may have changed since I checked.

Can't make assumptions...

 

[TallPaul]

quote:

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Originally posted by VaderSS:
While looking for a high grade gear oil that was not Group IV/V, I found that all synthetic gear oil(for major companies which is who I contacted) were actually IV/V

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So the Valvoline Synpower gear lube I put in my other two vehicles may be real synthetic. Still would go Redline next time on all vehicles. I think the redline is even cheaper at 7.95 a quart than the Valvoline Synpower gear lube.

Maybe the court case Castrol won only applies to motor oil, not tranny fluid, gear oil, or grease.

 

[Grossomotto]

I run Redline 75W90 which I think is the best gear oil on the market. You can get it for $6.98 at the link below. Anything else is just gear oil!

Sorry, no links to sales pages. Thanks.

[ July 11, 2004, 03:18 PM: Message edited by: 59 Vetteman ]

 

[VaderSS]

As of April 2002, Valvoline's(and every other major name brand's) synthetic gear oil was PAO. Don't know if that is still the case.

 

[Chris B.]

My 2003 Silverado requires Synthetic rear end oil. I've been using M1 75w90 sence 8,000 miles and no leaks at 20,000 miles.

 

[southernjeeper]

what does PAO mean?

 

[TallPaul]

I looked at the Valvoline gear oil MSDS's. They are a couple years old, but apparently still valid. For the Synpower Full Synthetic 75w90 Gear Oil the MSDS says "Semi Synthetic Lubricating Oil," 100 percent. So according to that the Full Synthetic gear oil is semi synthetic, which at best would be a Group 3. But I think the whole MSDS for this one is suspect when it says 100 percent lubricating oil. Even the Durablend gear oil MSDS includes 0-11 percent "Gear Oil Additives." But for the cost and the reputation, I plan on going only Redline for gear oil from now on.

 

[Jimbo]

Valvoline Synpower gear lube must be all PAO because my GM 8.875 axle developed a seal leak almost immediately.

Redline contains esters, so seals should not be a problem. I just put Redline in the BMW. It cured the chatter in the limited slip unit. Mobil 1 claims to not need additive, but it was chattering in tight turns.

 

[VaderSS]

Almost all sythetic gear oils contain friction modifier, though not necessarily enough to prevent chatter.

Two exceptions are Redline 75W90NS and NEO 75W90EP which contain none, and are perfect for use with Torsen type LSDs where you do not want FM.