Hello all, I have a 1992 Jeep Cherokee and it has a standard transmission. I need to rebuild the transmission and I want to do it myself. The sync rings are going bad. It started with the third gear, so I just drive with 1, 2, 4, and 5 gears, but now, the 4th gear is going out. Its time for me to rebuild this thing. Does anyone know where I can buy the parts, like a rebuilt kit or just the sync rings? I have done some research on line, but I am not sure if there are different sizes in rings so I thought I reach out for information here.

 

Plenty of kits out there, for example https://www.drivetrain.com/parts-cat...n-rebuild-kits. I'm not sure the differences in quality are though. There was a change in one of the synchros through the years, I don't recall if it was the 1st or 5th gear synchros, but I do recall some of the kits just included both versions. A master rebuild kit is ballpark $300 and will usually include all the bearings, synchros, and small parts. Sometimes the do not include the big input bearing, which usually doesn't need replaced. You will want a bearing press, or at the very least a gear puller with really long arms. The factory service manual will be invaluable too, as it's not obvious how a few things come apart. Also don't use GL-5 gear oil. Go redline, symnchromesh, etc (google and you'll see plenty of discussion on why)

 

Thank you very much lawsoncl, I will look into it.

 

Try Midwest transmission, or Rockland Standard transmission, both specialize in manual transmissions and there is a lot of good info and parts on both websites.

 

Novak might be a good source too.

Gootz, do yourself a huge favor and search the forum here for a thread where they talk about the owners manual and Factory Service Manuals being in error on the transmission oil and a Factory Service Bulletin about it. The manuals call for 75-90 GL5 oil. The problem with that is the anti wear additive in it is sulfur. Great stuff with steel hypoid gears. Bad stuff with yellow metals like bronze bushings and brass synchro blocking rings.

What happens in steel gears under pressure: the sulfur get mashed onto the steel and forms a micro thin layer that keeps the steel from rubbing the other steel when the oil gets squeezed out between them.
In REALY extreme cases the sulfur micro layer will peel off as a sacrificial.

In yellow metals the sulfur bonds with brass and bronze at the molecular level. When it gets peeled away it takes micro chunks of the brass or bronze with it.

Bob Is The Oil Guy has more information and knowledge about lubes oils and greases in one place than any wholesale distributor of lubes oils and greases does. They will have more better info than me.

.I found the following at advanceadapters.com/tech-vault/ajeep-ax15-transmission-used-in-1989-99-jeeps/

"The factory Jeep service manual initially called out 75-90W GL-3 gear oil for the AX15 transmission. We have also seen in later service manuals where Jeep was recommending some lighter weight oils.We feel Jeep may have “flip-flopped” on the oil recommendation to offer cleaner shifts especially in colder climates.The AX15 transmissions (supplied by Advance Adapters) calls for Mopar part# 4761839MA as the recommended oil.The AX15 will require the purchase of 4 quarts of oil. As outlined by a Jeep service manual, fill the transmission level to the bottom edge of the fill hole plug (about 3 ¼ quarts) and no less than ¼” below this level "

 

wow, thank you very much ijeep, That explains why the sync rings go out. I will look into it. I plan on doing the rebuild in December so I hoping my tranny can hold on just a little longer.

 

Thank you for the info 00t44e, thats what I have been looking for. I will look into it.

 

I put 15w40 Diesel oil in my AX15, it shifts great, and it doesn't have the synchro eating additives that most gear oils do.

 

15W40 eh? How's it shift when cold? The spec'd 75W-80 oil is pretty close to a 5W30 viscosity-wise, and I've heard of lots of people running 5W30 Mobil-1 engine oil. MTL and syncromesh both advertise having friction modifiers to improve synchro engagement, whereas gear oil is too slippery under pressure due to the EP additives. I'd suggest the OP do an oil change and see how much that helps. I put in cheap NAPA GL-4 gear oil after I rebuilt mine, planning to change it again in a week to MTL. The GL4 shifted so bad when cold, I thought I buggered the rebuild. MTL shifted great. Watch for that gold glitter in the oil. :{

 

I had no problems shifting it when it was cold.

 

Thank you lawsoncl, hum... thats interesting. My transmission won't catch third gear anymore, when I release the clutch, it will kick out my shift stick, then I started to just hold the stick in gear, release the clutch, and it will hurt, but it will get the gear. I have stopped using third gear, but now the fourth gear is starting to do the same. At this point, do you think changing the oil will help? Im willing the trying it if it could buy me more time. I won't be able to work on my tranny until mid December. Thank you for the info.

 

If it were just poor engagement, then a fluid change could help it. If you're to the point of it kicking out of gear, I think the synchros are pretty trashed.

 

you are correct lawsoncl. Thank you for the info.