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Rear End Oil

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Alabama_Hokies

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I have looked through the forum trying to find information. I have found some but could not find the exact answer. I have a 76 Spitfire and I need to put oil in the rear end. I can not find any GL-4 oil. Even the synthetics are GL-5. Suggestions of proper oil that I might be able to find would be greatly appreciated.

Thanks,

Dave B
 
I have been running Valvoline full synthetic GL-5 in my TR3A differential for some 20 years and over 150,000 miles of hard daily driving on LA freeways plus occasional excursions to the mountains and deserts. Far from causing any problems, I credit it for making the differential last as long as it has, because it was already well-worn when I got the car in 1984.

I can't speak for all synthetics, but the Valvoline at least does not use the additive found in some GL-5 oils that can cause problems in Triumph differentials. IMO it would be a fine choice for your Spitfire.
 
Randall, this weekend I picked up the Red Line MT-90 (also a full synthetic... but GL-4 rated) for my Spitfire gearbox. Am I correct assuming that would also work well in the differential.
 
dklawson said:
I picked up the Red Line MT-90 (also a full synthetic... but GL-4 rated) for my Spitfire gearbox. Am I correct assuming that would also work well in the differential.
Click to expand...
Well, I have not tried it; and I probably won't. Paying that much for a lubricant that deliberately has a high coefficient of friction seems counterproductive to me. And Redline states "MTL is not designed for use in rear-wheel drive differentials."
https://www.redlineoil.com/whitePaper/13.pdf

Still, since it passes the GL-4 specs, it would probably be "OK". Certainly it won't have the problem with the additive attacking the "yellow metal" thrust washers that some GL-5 oils have.
 
I used Valvoline a non-synthetic, I believe. At one time I used the oil closets to molasses and uit seemed to quiet the worn and noisy diff. T.T.
 
TR3driver said:
dklawson said:
Am I correct assuming that [Red Line MT-90] would also work well in the differential.
Click to expand...
... Redline states "MTL is not designed for use in rear-wheel drive differentials."
https://www.redlineoil.com/whitePaper/13.pdf

Still, since it passes the GL-4 specs, it would probably be "OK"....
Click to expand...
I'm no expert, but at a quick glance at the above paper, I see no mention of the MT-90 being an EP or Extreme Pressure lubricant, which I believe is generally required in most "hypoid" rear-drive differentials? Certainly, Triumph manuals tend to emphasize that point.
 
I found mine on the shelf at O'Reilly Auto Parts several months ago. It was some non-mainstream brand (at least not one that I recognized immediately), I'm guessing some smaller outfit producting GL-4 has found a niche in continuing to produce it while others have discontinued it. Look at the labels.
 
I called every local store brand, NAPA, Advance, Autozone O'Reilly- No joy.

Someone in my local car club then supplied me with this:
NAPA pn# SL24229

Wow! The NAPA store that I called yesterday had no GL-4 Gear oil. When I gave them the part number today they actually had the oil, and it is listed & labeled as, get this, GL-4 Gear oil..... aaarrrrgggg!

My wife is picking up thier entire supply- 3 bottles.

Dave B
 
Thanks again all. I'll save the MT-90 for the gearbox and find one of the other lubes mentioned for the rear end. As always, I appreciate the advice.
 
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