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H-Man 02-11-2013 08:20 PM

Need an oil for my gearbox.
My 1994 Geo prizm (Toyota corolla) has a 5 speed manual. It shifts like garbage when cold, I am running this (75W-90 GL5 > Products > Grease Gear Oil > Gear Oil > SynPowerŽ Full Synthetic Gear Oil )in it. By garbage, I mean that it is almost impossible to avoid crunching in the lower gears when it is cold.
What gear oil should I use?

HydroJim 02-11-2013 08:24 PM

Pennzoil syncromesh is one that a lot of people use in manuals. I'd do a little research before you make a decision. Could also be possible that your syncros are shot, but hopefully a better fluid will clear things up for you.

star_deceiver 02-12-2013 11:31 AM

Do not use a GL5 oil... Go out and buy some Redline MTL or MT-90 GL4 manual transmission fluid. You will notice the difference immediately.

I once swapped in a GL5 oil in my old '09 Vibe. It was instantly hard to shift and after the first day, became impossible the shift into 3rd without double clutching. Different transmission, yatta yatta... but the premise is the same, you can read up on the poor performance of gl5 fluids in small cars on many forums.

Red Line Synthetic Oil - Gear Oil for Manual Transmissions - MTL 70W80 GL-4 Gear Oil

You can find this product stocked on the shelf at most hotrodder/aftermarket performance shops. Napa ect won't stock it.

some_other_dave 02-12-2013 05:41 PM

Do you have an owner's manual? If so, it should tell you what kind of oil to use in the gearbox. Some newer manual transmissions actually use ATF, so a regular gear oil would be far too thick for them.


H-Man 02-12-2013 05:51 PM

The manual for the geo prizm says that I should use SAE 75w-90 GL-4 (GM part number 12346074 Castrol Syntorq GL-4 or equivalent) or SAE 75W-90 GL-5 gear lubricant.

UFO 02-12-2013 06:56 PM

I love the Redline MTL.

BHarvey 02-12-2013 09:52 PM

+1 for Redline MTL. Helped my car shift better in cold conditions.

H-Man 02-14-2013 09:37 PM

If I have to buy a gear oil at a B&M, what would be recommended?

star_deceiver 02-14-2013 11:41 PM

Buy Redline MTL or MT-90 GL4. Nothing else. Any GL5 product you put in your transmission will do the exact same thing it's doing now so don't cheap out. Find a store that sells Redline or buy it online and have it shipped.

No compromise!

razor02097 02-15-2013 07:32 AM

If the syncros are brass your sycros are quickly being destroyed by the GL5 oil.

Here is an article that helps explain why you should not use a GL5 oil in a sycromesh transmission.

H-Man 02-15-2013 11:23 AM

I found a GL-4 locally that I can run to get the LSD additives out of the gearbox while I wait for whatever synthetic I use to get here.
I've been shifting it like a crash box, rev matching with every shift, so I think the syncros may still have life in them.
EDIT: I found a local supplier of Amsoil MTG, it so happens that this replaces the exact oil GM recommended for my Prizm.
EDIT2: This stuff is so smooth. Grinding gone.

some_other_dave 02-21-2013 05:10 PM


Originally Posted by H-Man (Post 356472)
If I have to buy a gear oil at a B&M, what would be recommended?

Since I at least don't have any clue what they would carry, all I can tell you is:

Get a 75/90 weight GL4 oil. Any brand will do, but the higher-quality ones should work better and last longer.


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