Recommended manual transmission fluid?
Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 878
Likes: 60
From: Minneapolis, MN USA
Recommended manual transmission fluid?
Hi all - planning to reinstall my rebuilt motor and tranny this weekend. What do you all suggest for manual transmission fluid? I want to put "good stuff" in it.
Thanks - stay healthy!
Thanks - stay healthy!
Instructor
Joined: Nov 2019
Posts: 221
Likes: 71
From: Kalispell, MT
Depends on the trans. Some manuals with bronze blocker rings (syncro's) don't shift as well with synthetics as they do with petroleum based lubes. GL5 can cause corrosion of bronze blocker rings. So for an older trans like the Borg Warner T10 or Muncie, I'd go with GL4; you can't go wrong. But GL4 is getting hard to find. If you want the best in my opinion, go with Red Line MTL GL-4 full synthetic. That's what I'll be using in my ZF six speed. I have been using Red Line lubes in my Harleys for 25 years and they perform exceptionally well in the straight cut gear boxes. You can get it on Amazon.
Last edited by C3TPI; Jun 23, 2020 at 10:18 AM.
Burning Brakes
Joined: Jan 2001
Posts: 1,004
Likes: 16
From: Gainesville, Florida
If you have a Muncie, use Sta-Lube GL4 (85W90). The "good stuff" isn't necessarily the best for 50+ year old transmissions. I've used it for years. Most old school Chevy guys use it. I recommend staying away from synthetics (too thin & slippery) & GL5 (corrosive to bronze).
https://www.napaonline.com/en/p/SLRS...lube+gl4+85w90
Mark
https://www.napaonline.com/en/p/SLRS...lube+gl4+85w90
Mark
Last edited by gearheadz; Jun 23, 2020 at 11:03 AM.
Racer
Joined: Jan 2008
Posts: 295
Likes: 58
From: Arvada Colorado
I race my car and have found that the non synthetic oils work a little better. I have used Brad Penn in the past and now use Driven oil. These are GL-4 oils and are available from several on-line sources.
Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 878
Likes: 60
From: Minneapolis, MN USA
Thanks for the input! This is a "new old" transmission. It's the original 50 year old transmission (4-speed), but was just rebuilt, including replacing gears 2 and 3. Looks like the GL-4 is the thing...does brand matter much? What does anyone think of Royal Purple? I believe it's full synthetic tho...
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
Likes: 1,213
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
I switched from gl5 redline synthetic to lucas 85-140 non-synthetic. It does shift a bit better. Btw, redline gl5 syntetic won't damage bronze. It's stated on their website.
Le Mans Master
Joined: Apr 2001
Posts: 5,941
Likes: 281
From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
Burning Brakes
Joined: Jan 2001
Posts: 1,004
Likes: 16
From: Gainesville, Florida
Thanks for the input! This is a "new old" transmission. It's the original 50 year old transmission (4-speed), but was just rebuilt, including replacing gears 2 and 3. Looks like the GL-4 is the thing...does brand matter much? What does anyone think of Royal Purple? I believe it's full synthetic tho...
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Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 878
Likes: 60
From: Minneapolis, MN USA
Gotcha - thanks for the input. Sounds like the Sta-lube 85W90 is the way to go!
Le Mans Master
Joined: Mar 2004
Posts: 7,502
Likes: 1,509
From: Little Rock AR
GL-4 conventional gear oil in an old gearbox. Brand is not as important.
Some well respected guys do recommend synthetic but I have had issues with seal leakage, shift feel and noise with synthetic lube so the cheaper old school conventional gear lube fixed those issues.
I build my own gearboxes.
Some well respected guys do recommend synthetic but I have had issues with seal leakage, shift feel and noise with synthetic lube so the cheaper old school conventional gear lube fixed those issues.
I build my own gearboxes.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Metal-to-metal wear rates with full synthetic products is SOOOO much lower than with organic products, switching is a no-brainer. Thinking that 'old' mechanical parts can't benefit from full synthetics is just like thinking that EFI can't work on an old engine.
You just need to find out which synthetic is the best for your particular transmission.
You just need to find out which synthetic is the best for your particular transmission.
Le Mans Master
Joined: Oct 2007
Posts: 7,455
Likes: 977
From: RI, Now Franklin/Nashville TN
In fact, most GL5's specifically note, the wive's tale, that modern GL5's will degrade bronze synchros....they will not. Also, My 78 Super T-10 specifically notes GL5 in the owner's manual and backward compatible to GL4 which indicates more about the bronze erosion issue which probs came about early on with the introduction of GL5 fluid but was quickly corrected and the myth lives on with modern fluids.
As noted above, another wife's tale that conventional oil is better for old school tranny's..not a chance. A super synthetic lubrincant has no idea whether the gears and seals are old or new......
Last edited by jb78L-82; Jun 24, 2020 at 10:03 PM.