Possible to Repair Synchros?

'Usually' that means someone has put the wrong tranny fluid in it. The 'correct' stuff is hard to find. The right stuff has a GL3 rating. All the crap I could find on the shelves is listed as GL5 compatible which will make synchros not work.

If you change back to the correct fluid, it might come back to life. My T-5 did.

You might want to check the routing of the heater hoses. If the top one is above the level of the coolant in the rad, it can air lock easily stopping most of the heat. A good flush of the heater core works wonders too.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

Thanks Mike - I will try to locate some GL3 rated transmission fluid. Should I completely drain what I have currently? If so, (this is going to sound like a naive question) is this a simple process? I am a Jeep newbie.

You're the man Bill - if trying the new tranny fluid does not remedy the problem, do you think replacing the synchros is the way to go. How do I know if I have an AX5, AX4, or AX15?

Never heard of an AX-4 on a Jeep. The AX-5 comes with four-bangers, the AX-15 comes with the six cylinder. When you add gear lube, do drain out what's in there and replace it with a GL-3 or GL-4 like Redline MT-90 which is really the only aftermarket gear lube that meets the specs for both the AX-5 and AX-15.

Jerry

macgraphics wrote:

Thanks Jerry - Once I drain and replace, how soon (do you guess) I should know whether on not this remedies the problem?

I would highly recommend you get at least one of the inexpensive manuals like the Haynes. It gives all the basics and settings for everything and is real handy when tinkering around on them.

You will find 2 bolts the same on the tranny. One will be in the very bottom and a second looking exactly the same will be in the side about half way up.

It is easy to drain but a bit of a pain to fill. I usually add a chunk of gas line to the end of the oil bottle which helps getting it back in. I also warm the oil up first. Molasses in January has nothing on cold gear oil.....

Mike

macgraphics wrote:

I wouldn't expect a cure or anything dramatic. Some have had some success by switching to this particular gear lube but if you truly have a synchro problem, it's not going to make a noticeable difference. It's worth a shot though, you're not out a lot of $$$.

Jerry

macgraphics wrote:

My T-5 came back to life within a couple days. The crunch when downshifting and I had one upshifting cold went away really fast.

Mike

Jerry Bransford wrote:

Mike, being from the frozen North, you would appreciate this. Here I was stationed in Wisconsin after living in far more temperate climes all my life. Busted the cross shafts in the front diff of my old Scout. I unlocked the hubs and got it home, but I had an unheated garage and it never got up to zero (F) that week. Pulled the cover off the diff and had my first inkling of trouble - the gear oil didn't even try to run out. I stuck my hand in that goo to pull the pieces out and I don't think I have ever felt anything as painful as that sub-zero gear oil!

I doubt that what doesn't drain out will cause any problem. The only way I know to get it all out is to crack the case and that still leaves a little bit coating the gears and bearings. Just let it set and drip for a while if you are concerned about mixing the oils.

Thanks Will - I picked up a Haynes Manual today, looks like I have some heavy reading to do. I also picked up 4 quarts of Redline MT 90 and I plan on changing the fluid sometime this week. Hopefully I meet with the same results you did. If not I found a Transmission Repair Kit at Advanced Auto Parts for under $50 (it is on sale, typically @ $90). Do these types of kits usually contain synchros? Does this seem like too low of a price? Do you think it is worth a shot before a tranny replacement or rebuild? Thanks again for all your advice - Mark

I should have addressed that note above as Thanks Mike and Will, my bad. - Mark

Replacing synchro's is not a newbie project. There are a fair number of shimmed shafts and enough other nasty parts to make reassembly a bit problematic. Plus you can figure about 6 hours to remove and replace the tranny in the vehicle

I'd expect he $50 kit to include gaskets and the synchros but not much else. Especially no bearings. You really should find out what is in it before ordering.

I would not tackle this without the factory manual. Or at least make sure you have BOTH the Hayes AND the Chilt> Thanks Will - I picked up a Haynes Manual today, looks like I have some

I'm with Roy here. It's not that difficult to replace the syncros but there are some tricky setup pieces in there. You will need a GOOD pair of snap ring pliers - none of the Harbor Freight cheapies - and a really good diagram. There are a few place in the AX-15 where you have to know the correct sequence of what to pul next to get it all apart and it is essential to keep track of the number, size, and sequence of the various spacers. Several places are almost a press fit - tight - so I wouldn't advise trying it w/o a good shop manual. I bought the AX-15 manual separate from the rest of the Factory Service Manual when I swapped out my old Pugeot 5-spd and I think it was only $15 - $20 from Chrysler. One thing no one mentioned: you will want a CLEAN, sturdy workbench and a good sized vise - at least 6 inches, maybe 8.

Not a newbie project, c> Replacing synchro's is not a newbie project. There are a fair number of

Hi guys. I just found this site, and topic. What a help! I have a 91 Wrangler 4 cyl, my youngest son bought when it was 3 years old. I just bought it from him last summer. (170,000 miles) Dear old dad has done most of the work on it during the years. Replaced the motor a few years ago with a re-built....About 20,000 Miles on motor. About 2 years ago the syncro's started making a noise when shifting up, only between 2nd & 3rd. Now about in every gear. Glad to hear about the Redline MT90. I will try that before removing the tranny, or replacing. My chain in the transfer case also slips. On icy roads, in

4H, really slips. When going to hunting camp through muddy roads in 4L, only slips occasionally. Other than that the old girl ain't to bad. Good for riding the gravel backroads here in eastern Maine!!

jack

Double clutching is good, much better than tearing transmissions apart in the garage or basement. That chain slipping would have me worried though.

Earle

If that chain in the tc is slipping, you gotum big problem! That's a sprocket driven chain and if it's loose enough to jump a tooth or 3 then it is also loose enough to be eating the case away. You sure it's not just jumping out of 4WD? That's a simple fix - adjust the shift rod. One 13mm bolt in the trunion that locks the shift rod in place. If the chain is actually stretched far enough to jump, then a rebuild on the tc is pretty simple as well. If you can swap an engine you can do that part.

Thanks Will & Earle. I have a Haynes manual, (which I get for every vehicle I have.) Helps alot on my 97 Dakota. My brother was a service manager at a jeep garage a few years ago, and said you used to be able to take the transfer case apart on the older jeeps. I will probably take it out, along with the tranny early this spring, and fix both, or fix the chain, and find a used tranny? God, why haven't I thought of looking up sites like this before?..lol. I have learned more here in a hour than 2 months checking the Haynes, and wondering. Thanks again guys! I will probably bury all of you with questions...

jack