Omni GLH Turbo gearbox oil recommendations?

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Jul 6, 2004
Houston, TX
Just picked up a new project car, an '85 Dodge Omni GLH Turbo (Goes Like [censored]) with the 2.2L turbocharged engine. Updated to Turbo II specs with higher output turbo, intercooler, MOPAR computer & cam, and making around 20psi of boost (a tad over 220hp/300ft-lb torque). I was told it has the upgraded transmission over the original.

My problem comes when researching what to put in the gearbox. Several sites say that 5w-30 engine oil was used originally, leading me to believe that a lighter-weight GL-4 would be better (similar to earlier Hondas). The AMSOIL guide says to use Synthetic ATF for the manual transmission, leading me to believe that a synchromesh-type fluid can be used. Then on other performance turbo dodge sites, they use regular GL-5 oils in 75w-90 weights. Too many choices!

Any real-world experiences? This will not be a daily driver, but a track/autocross car...different animals--- autocross will see cold-start with little to no warm-up and 100% thrashing on it, while track racing will be warm-temp with plenty of warm-up but much higher trans/engine temps and loads over a longer period of time(20-30 minute sessions).

I had that exact same car!!!!!!

Bumped the turbo boost from 7 to 14 PSI.

Kicked buttt!
What transmisison, the orignal A525 or has it been upgraded to the A555 getrag??

I have a 86 Datyona CS. I converted it to T2 and installed a A555. Anyhow it doesnt really matter.

Originally they came with ATf but in 88 or so they started using 5W-30 engine oil in them.

Myself I run Amsoil MTF in them. I also have a Shadow built up and repalced the 520 with the 555. I ran 5w-30 AMsoil for 190K miles in that one and the same 5w-30 a A523 transaxle in my other Daytona.

The Amsoil MTF is good, same viscosity as the 5w-30 but has better properties to protect the gears and diff.

Do not use 75W-90. Whoever is telling you that doesnt have a clue. I have run these cars for 20 years so I know a little about them;)

How does the car run, do you have the orignal mechanical linkage or did someone convert it to cable. If your running the 525, watch the axles and the intermediate shaft. I have a few hanging around in my basement. They are getting hard to find.
Congrats on the GLH! I gained a lot of respect for those little hoovers on wheels after watching them run with the Hemi and six-pack cars at the track, then drive home getting 25+ mpg.

I agree, don't use GL5. If 5w30 was recommended, then that's around the viscosity of Redline MTL, Royal Purple Synchromax, and the like so those should work well. If you want to try a 90-weight GL4, I'd recommend Redline MT-90, also hear good things about Shaeffer's gear lubes but never used them.

BTW- if you're really hitting 20 PSI boost and everything is working, that 220 HP/300 ft-lb estimate is probably low. Way low ;-)

Of course if you're hitting 20 psi boost, everything else had BETTER be working. Dipping a little lean at those boost levels is a bad, bad, bad thing. I assume its already set up with high-flow injectors and/or auxiliary upstream injector(s) to keep the fuel flow up at high boost?
I find this question interesting as well. The transfer case in my duramax is spec'd for ATF but there are a ton of people running 5w-30 synth in them.

There was a trade paper posted in a transmission rebuilder's journal stating that in order to address the transfer case's propensity to have bearing surfaces actually wear through the aluminum transfer case they recommond 5w-30 synth rather than ATF. It was a well researched paper with documented proof of the recommendation.

The recommendation was on the basis that the tcase got so hot it was burning off the ATF and the tcase would go low then wear through. The recommendation was on the basis that 5w-30 had better properties in this regard.

A great number of people have switched over to 5w-30 in their tcases after replacing them due to the ATF problems, and are putting significantly high miles on them with no further problems.

I will do the same when I am out of warranty, but I find it interesting that in some applications ATF and 5w-30 seem to be essentially interchangeable.

Can anyone comment on the similarity of these two fluids that would render them both a good gear box lube?
Originally Posted By: Jim 5
Great car by the way. My favorite use of this mopar turbo is at

I've "known" Demspey (owned "Clifford (the big red van)" and "Bluesmobile" on that site) for many years, back to the old Mopar Mailing List days in the 90s. Absolutely amazing stuff those guys do.
Once it's up and running better (diagnosing a fuel pump issue, may have to just run a dedicated relay and wiring...heck, it's a track car), I'll probably go with RedLine or AMSOIL in their MTL formulas. Thanks guys!
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