View Full Version : What type of oil for Muncie?


YoungCamaro
09-20-2009, 02:28:08 AM
Just bought an m20 wide ratio muncie. I'm going to be installing it tomorrow and i'm wondering what type of gear oil and how much I need to put in it?
The chilton's manual I have said 3 pints and the guy I bought it from said 2 pints.
I put 2 pints in tonight and its right below the bottom of the drain plug, should I add more?

Also I've read a lot about gl-5 oils ruining the brass synchros, so what weight should I use?

Please comment if you have experience with muncie 4 speeds. Thanks

warped
09-20-2009, 04:03:26 AM
Filling the case to the bottom of the fill hole is the proper way. As for the GL5, it is not a weight, but a designator for a certain level of additives. In general, you want to stay with a GL4 rated gear lube, but recently there was a post that certain manufacturers have now offered a GL5 rated lube that will protect the brass synchros. Once Gary gets up and posts, I'm sure he will be more informative. Good luck.

Gary S
09-20-2009, 04:37:51 PM
You want an 80-w90 or 75-w90 oil. It needs to be a GL4 rated oil, not GL5 rated. We had a post here recently about some of the synthetics being rated for both GL5 and safe for brass syncronizers, but I can't find that post.

YoungCamaro
09-20-2009, 06:32:46 PM
Thank you for the responses I'm going to look for some gl4 80-w90 at the local auto parts store this afternoon and see if they have any. Thanks again

Dave Nelson
09-20-2009, 08:23:50 PM
Your GM dealer has GL-4 part #89021672

YoungCamaro
09-21-2009, 06:35:13 PM
Your GM dealer has GL-4 part #89021672

thanks

Caperns
09-21-2009, 11:23:13 PM
GEAR AND SYNCHRONIZER WEAR PROTECTION
Most manufacturers of manual transmissions and
transaxles recommend an 80W or 90W GL-4 lubricant.
GL-5 gears oils which are required in hypoid differentials
are not used in most synchromesh transmissions
because the chemicals used to provide the extreme
pressure protection can be corrosive to synchronizers,
which are commonly made of brass or bronze. Typically,
the use of a GL-5 lubricant in a synchromesh
transmission will shorten the synchronizer life by one
half. The extreme pressure requirements of spur gears
and helical gears found in transmissions are not nearly
as great as found in rear-wheel drive differentials. A
GL-4 lubricant provides adequate protection for most
manual transmissions, unless a unique design
consideration requires the extra protection of a GL-5.

YoungCamaro
09-22-2009, 05:20:14 PM
GEAR AND SYNCHRONIZER WEAR PROTECTION
Most manufacturers of manual transmissions and
transaxles recommend an 80W or 90W GL-4 lubricant.
GL-5 gears oils which are required in hypoid differentials
are not used in most synchromesh transmissions
because the chemicals used to provide the extreme
pressure protection can be corrosive to synchronizers,
which are commonly made of brass or bronze. Typically,
the use of a GL-5 lubricant in a synchromesh
transmission will shorten the synchronizer life by one
half. The extreme pressure requirements of spur gears
and helical gears found in transmissions are not nearly
as great as found in rear-wheel drive differentials. A
GL-4 lubricant provides adequate protection for most
manual transmissions, unless a unique design
consideration requires the extra protection of a GL-5.

thank you also I will drain the gl5 out and replace with some gl4

jb71camaro
09-22-2009, 05:46:27 PM
Good to know, I'm getting ready to fill my M-22. Would suck to use the wrong stuff and have to rebuild again.

cubfan226
09-22-2009, 10:53:58 PM
...Most manufacturers of manual transmissions and
transaxles recommend an 80W or 90W GL-4 lubricant.
GL-5 gears oils which are required in hypoid differentials
are not used in most synchromesh transmissions...

A while back I drained my non-limited slip differential with 3.08 gears and was directed toward some Valvoline 80w-90 GL5 gear oil. I refilled the diff, but have run less than 100 miles on this gear oil. Is the GL5 ok for this diff, or can the diff be damaged by the GL5? I don't know what a hypoid diff is, but I expect my diff is the original (1970). Thanks.

YoungCamaro
09-26-2009, 09:57:48 PM
I just bought some pennzoil synchromesh manual transmission fluid. It says it compatible with yellow metals such as bronze brass and copper. Do you think this would work good in a muncie or not?

http://www.amazon.com/Pennzoil-Synchromesh-Manual-Transmission-3501-C6/dp/B000BIRJ6E
Link is the oil

Gary S
09-26-2009, 11:58:45 PM
A while back I drained my non-limited slip differential with 3.08 gears and was directed toward some Valvoline 80w-90 GL5 gear oil. I refilled the diff, but have run less than 100 miles on this gear oil. Is the GL5 ok for this diff, or can the diff be damaged by the GL5? I don't know what a hypoid diff is, but I expect my diff is the original (1970). Thanks.

GL5 is the correct oil for differentials. It is just not for older transmissions. You have the correct oil in your diff.

Gary S
09-27-2009, 12:05:14 AM
I just bought some pennzoil synchromesh manual transmission fluid. It says it compatible with yellow metals such as bronze brass and copper. Do you think this would work good in a muncie or not?

http://www.amazon.com/Pennzoil-Synchromesh-Manual-Transmission-3501-C6/dp/B000BIRJ6E
Link is the oil

No. From what I can find, Pennzoil syncromesh tranny oil is a 30 weight oil for front wheel drive trannys. Old Muncies, Borg Warners, and Saginaws need a 75-90 or 80-90 oil.
Unless you can find a 75-90 or 80-90 weight of Pennzoil syncromesh, don't put it in your Muncie.

yobin67
09-27-2009, 01:26:17 AM
When I ran a 4 speed,this is what I ran. http://www.amsoil.com/storefront/mtg.aspx Good stuff.I have their products in all of my vehicles.

Gary S
09-27-2009, 12:12:59 PM
Amsoil's GL4 MTG is an excellent choice for a Muncie tranny because it is specifically made for these trannys.
Even Amsoil's GL5 rated differential lubes SVG and FGR are suitable for Muncies because good synthetic oils don't use the corrosive additives needed in mineral oils to achieve the GL5 rating.
However, I recommend the GL4 MTG over the SVG or FGR. The MTG lube gives smoother shifting.

YoungCamaro
09-27-2009, 04:47:53 PM
okay thanks gary for the info I think I will look into the amsoil gl4 mtg.

cubfan226
09-27-2009, 05:17:40 PM
A while back I drained my non-limited slip differential with 3.08 gears and was directed toward some Valvoline 80w-90 GL5 gear oil. I refilled the diff, but have run less than 100 miles on this gear oil. Is the GL5 ok for this diff, or can the diff be damaged by the GL5? I don't know what a hypoid diff is, but I expect my diff is the original (1970). Thanks.


GL5 is the correct oil for differentials. It is just not for older transmissions. You have the correct oil in your diff.

Thanks Gary!