Alex89

I hate to beat a dead horse but I've spent hours searching and reading about which manual transmission oil to use. My only conclusion is there is a lot of contradicting advice out there. The question is simple: what lube goes in 951 UY transaxle? Open diff, no cooler.

I'm still not clear on GL4/GL5 ratings. My manual says 80W GL4. Apparently a Porsche bulletin says GL5?

So what do the experts suggest? My current short list is as follows:

Locally available:
Motul Motylgear 75W90 - "GL4 and GL5" - My current first choice
Royal Purple Max Gear 75W90 - "GL5 or GL4" - More expensive then Motul
Amsoil - Whatever is suggested. See my experience below.

Other options I can buy online and import into Canada (which seems ridiculous):
Mobil 1 75W90 LS
Redline MT90 or 75W90? - Most expensive/complicated option to buy. I've seen many contracting opinions around MT90.

Anyone following my restoration thread knows I previously used "Amsoil 75W90 Long Life Synthetic Gear Lube" (API GL-5 & MT-1) with devastating results after only 50 miles. I can't definitively point a finger at this lube but my replacement transaxle is on order and I don't want a repeat experience. Advice would be greatly appreciated.

mrgreenjeans

Am definitely NOT an expert, but it seems all have had great experiences with everyone of those oils mentioned, except I know nothing of the Amsoil product.

Personally, I have used the SWEPCO 201 in my cars for both track events and street use and have never had any issues. They have Limited Slip ( except one ) and the cool thing is, one does not need a 'friction modifer' additive in that product for LSD. It is a superior lubricant but quite expensive.

You are going to get quite a few diverging comments, so now that the Pandora's Box is open .......

wildcat077

Strange coincidence about the Amsoil gear oil ... i have two cases of their Dominator 15w50 oil that i plan to use in my race engine this season !
Yikes ...
As for the transmission oil , my cars like the Mobil 75w90 which i buy in 20 liter pails for both the race car and my 911

Alex89

Swepco is probably the most complicated / expensive to import, probably over $100 when I'm done. If that's the best option then I'll do it but it seems crazy to me.

I do like what I hear about the Mobil 1 oil. Can you confirm that's the "LS" oil? It is the least painful to import.
Buying Motul or Royal Purple would be so much easier but I took the easy route last time and now will never know if it caused me problems. The car had sat 10 years when I bought it with no history. I drained clear (old) fluid from the transmission, refilled it with the Amsoil stuff, took it for a couple test drives and then a grinding noise began from the rear end. Ruled out CVs, so drained the fluid to this result:


I've since found an issue with the parking brake that probably added to the noise when the car was in motion, but I couldn't ignore the oil. I took the transaxle apart and was advised it needed a full rebuild. My car isn't worth that kind of money so it's getting a used UY from Lart. Again I can't say for sure it was the oil but I want to be sure I use the right stuff moving forward.

wildcat077

The Mobil Delvac oil is readily available in Canada , you don't have to import it ...
Last time i paid $180.00 for a 20 liter pail, as of last year the price was still around that figure !

Don't get mistaken with the Mobil oil they sell at CDN Tire, not the same thing

Alex89

Hi Nick, thanks for the detailed information. How does the Motul Gear 300 compare with Motylgear 75W80?
I'll have to inquire if Gear 300 is available but I know I can get the Motylgear if they are comparable. For the record this is a street-only application, non limited slip differential.

I haven't found a source for Mobil 1 gear oil but to be fair I wasn't looking for 20L pails... that's a multi-lifetime supply. Can I ask where you got it? This is the product I was considering (available on amazon.com):
https://mobiloil.com/en/gear-lubrica...c-gear-lube-ls

wildcat077

Any Canadian Mobil/EXXON supplier carries the product , i believe you can also get it in 3.78 liter jugs ...
With the two cars and the race car getting two oil changes per season it's worthwhile for me to buy a larger quantity !

Go on the website and search in the Heavy Duty products section , then select rear axle, it will give you some options.

Karl_W944

All I can weigh in on is Redline MT90 75W90. I've ran it in my '84 944 and currently run it in my '80 931. It improved shift quality and my driving experience in both cars. Can't say whether or not it's better/worse than the rest; only that it's a good option.

robmeister951

I've used CASTROL SYNTRAX UNIVERSAL PLUS 75W-90 Synthetic for 100k Miles in my daily driver 86NA since 2007

Specifically for transaxle tranny.

Perfect shifting hot or cold.

1933beer

In the rest of my cars I just change it. I put redline in my car several years ago. I think it still had the original. It made a difference in my worn sincros. I recommend it.
In your situation limited options I would go with royal purple. If it doesnt help try to get something else.

Dan Martinic

When I last changed my gear oil, I used the here-in-Ontario readily available Liqui-Moly 75W-90. LM is supposed to be quality German stuff, though I have to say the one-two shift after cold start still grinds sometimes and generally no improvement over what I had before (unknown as a shop changed it about eight years ago).

Next time, I will be trying the Motul. Nick's pretty convincing

kervracing446

I’m using Millers Oils gear and engine oil. I’m based in Toronto and there is a local dealer. Most of the 944 Cup race cars are running it in PCA, they are also a sponsor in PCA club racing. The highlight of product is it has Nanotechnology in it. Micro ceramic nanoparticules.

wildcat077

Since you're in Ontario, you can always give Millers Oil a try , Bill Comat would be your guy and there is some sort of PCA or racer discount that
he can pass on to you.If i didn't have a prefered customer account with Amsoil i probably would have given his engine oil a try !