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Transmission Grind

8K views 25 replies 12 participants last post by  Old Dogger 
#1 ·
New member here...
Last week my wife and I bought a well used 1994 YJ. I have noticed a slight grind going into 2nd and a slightly more aggressive grind going into 3rd. Transmission is shifting fine into 1st, 4th, and 5th gears. I have NOT checked transmission fluid yet and I am pretty sure the fluid has not been changed in several years. I am almost positive the transmission is original and if the mileage is true the vehicle has 169K miles on it. Plans are to check fluid level towards the end of this week and ensure the level is not low. Beyond this I do not have a clue! I have several theories running in my head such as synchronizers, total transmission failure, fluid level/condition. Based on my research I am almost certain the jeep has an AX5 transmission but assistance in verification would be greatly appreciated. Motor is a 2.5L. This jeep has been a blast so far and have already successfully completed changing out the plugs, wires, distributor cap, rotor button, and very proud of this one!!!!!! Replaced the worn out sloppy steering box that was pouring power steering fluid! Thanks a bunch for any help/advice. Owning a jeep has been a dream of mine for the last 16 years and now it has come true!
 
#2 ·
Sounds like you may have worn sychronizers in transmission. Many have had luck using Synchromesh from Pennsoil as a trans lube. It is designed to be good in the brass parts. If that doesn't work you can rebuild AX5 or upgrade to the beefier AX15 which is a much better transmission. If you pull the trans replace the clutch and consider going back with an external slave cylinder set up if yours doesn't have one. These were available in 94 & 95. Not sure what model you have. Many write ups on this as the internal slaves all seem to fail out of the box. Good luck.
 
#4 ·
I have a similar issue, only not as bad. I changed my trans fluid (probably the original fluid) and used synthetic 10W30 with STP. I used that because none of the local parts stores has GL4 which is better for brass syncros that GL5. The fluid change produced only a marginal improvement. If I slowly and carefully shift into second it doesn't grind at all. I haven't tried double clutching because the issue isn't too bad and I just never think of it.

89yellowjeep's suggestion to convert to an AX15 is a better fix. Just be sure that the transmission that you install is in better condition than the one you take out.

Search this forum for threads on what it might take to do the conversion. The AX15 was behind 6cyl Wrangler motors starting in 1991 or 1992. Should be pretty simple.

Good Luck, L.M.
 
#5 ·
Thanks a bunch for the advice! I will certainly try changing the fluid first. I like the AX15 idea a lot. Can I swap out the synchros or is it cheaper in the long run to make the swap for a new transmission? I have heard if one part gets replaced its just a matter of time before you have to replace the rest. When the motor gives up the goast I will more than likely put a 4.0 in it. I know it powered my old XJ well so it should do wonders for the wrangler! Swap in some 44's for those Dana 35's and someone will have to come up with a good explanation for their wife on why the jeep is getting a suspension lift and 35x12.50's!!! J...ust, E...mpty, E...very, P...ocket! Did I mention how excited I am about this new/used Jeep?!
 
#6 ·
The Ford 8.8 is a more practical swap than the D44 and less expensive. The Ford 8.8 is available in 4:10 ratio and your front D30 is probably already 4:10.

Before you spend the dough on 35X12.5s, do some research. There is a recent post where a Jeeper went to 33s and regrets it. 31s are about as big as is practical for a 2.5.

Good Luck, L.M.
 
#7 ·
Yes I have read the post. This YJ is slowly going to transition as stuff fails. LONGGGGGGGGG term goal is small block Chevy with Dana 44's, 35's, 4Link, Exo cage, Body mods to assist in approach and descent, and who knows what other kind of fun stuff I can get in to!
 
#8 ·
You can always just pull your current transmission and replace the syncros. By looking at my Chiltons manual it doesn't look like too big of a deal.

I replied to your PM. I didn't realize that the PM came from a post that I had replied to. Now that I know the shop wants $2500.00 to replace the syncros, I think that is a bit steep. You seem to have a good handle on older Wranglers. If I were you I would fix the current transmission myself.

Good Luck, L.M.
 
#12 ·
You can always just pull your current transmission and replace the syncros. By looking at my Chiltons manual it doesn't look like too big of a deal.

I replied to your PM. I didn't realize that the PM came from a post that I had replied to. Now that I know the shop wants $2500.00 to replace the syncros, I think that is a bit steep. You seem to have a good handle on older Wranglers. If I were you I would fix the current transmission myself.

Good Luck, L.M.
$2500 ??? HOLY CR:censored:!

I had my AX-5 (I know, I know - AX5 sucks), completely rebuilt for like $700. I pulled it and dropped it off, but still.
 
#9 ·
Still exploring my options... This weekend I will find out for sure if the AX15 will bolt up. If it will I am going to find one in a junk yard that has a good housing and bring it home on the cheap. Then I will commence my rebuild. When the AX5 dies I will hopefully be in a position to just swap the two out. If it doesn't work I will at least know that I have no business in a transmission or maybe it will work great and I can give myself a small pat on the back. L.M. I will keep you posted on how all of this pans out down the road! Thanks for the help and the faith!
 
#10 ·
I Think a AX15 from a TJ Jeep with 2.5 will bolt right in, but as for as I know most all YJ's with a 2.5 had the AX5. the bell housing is Not the same for the AX5 and the AX15, but with some research it think one can be found in a Dodge Dakota 2.5 that will fit and AX15, but an AX15 from a 4.0 will Not bolt right in.
 
#11 ·
Synchros likely. Fluid next. All sound advice.
But easy-to-diagnose stuff like motor mounts or trans mount can also explain rough shifting.
I've had what I thought were bad synchos cured by new fluid once in another jeep and a new trans mount another time in current jeep. I did get a new tran$$ eventually but feel I lucked out those previous two times with shifting woes.
I've even had rough shifting between select gears, like you describe, from low clutch fluid/improper bleeding.
Synchos/fluid likely. I sometimes think I know a lot, but the people that replied to you are much smarter than me. Experience and just my 2 cents says to rule out the easy/unlikely stuff before sinking $$ in a new trans. I have dodged the $$$ bullet a few times with the easy/unlikely stuff I didn't think to check.
 
#13 ·
Thanks for all of the advice and helpful hints. Fluid change this weekend will either help it out or it won't. If it still doesn't work I will try checking mounts then synchronizes. I think I can pull the bell housing off of my ax5 and it should bolt up to ax15. Got a guy local with an ax15 that is going to let me measure bolt pattern on ax15 just to make sure. Thanks again for all of the good advice!
 
#14 ·
Update,
Okay so 3.3+ quarts Royal Purple 75W90 and a few beers later the transmission fluid has been changed. I considered synchromesh but after speaking to several local transmission shops I have discovered it will improve the issue but only for a short while. Apparently it starts to break down the "yellow metal". Royal Purple was $88.00 before tax!!! Price you pay when NONE of your local parts stores cary any other yellow metal safe gear oil! Made a few laps around the neighbor hood and here is where I am now.....
Third gear grind is gone! At least on upshift. (Couldn't get enough room to hit 4th and downshift) Second gear grinding is gone on upshift too! Down shift is still barking a little but it appears that my conditions have drastically improved! I am not sure if more time running transmission will make things slightly better or worse. Could it be that the change I noticed already is all that I will get from the situation? The fluid that was drained had some metal in it but no large chunks just very fine (dust like) sparkles. Wish I could have taken a picture but gear oil was put in container with used motor oil so there is no way to tell color or anything from it. The gear oil was a grey color. Is that normal? I was also told by a friend that my timing could be off and causing a problem with the grind??? I have never hear of this but thought I would ask. I intend to check my motor and transmission mounts and any linkage/bushings in the shifter that I can see tomorrow. Again, thank you ALL for your advice and help with this issue. Your comments are welcome and appreciated. I will continue to keep you all posted!
 
#15 ·
That a fluid change got rid of most of your problem is very telling, although I'm not sure what it means.

I don't know how to improve what's left to improve and I'm I am not convinced the trans isn't the problem.

Be curious what adjustments you do and what the results are.
 
#16 ·
Is the '94 clutch adjustable? If it is, make sure you have just a bit of freeplay between the slave cylinder rod and the outside of the clutch fork.
Other posters will be able to tell us if the clutch is adjustable.

Good Luck, L.M.
 
#17 ·
Adjusting the clutch is a pretty good idea! I am going to do a little more research on how to (if possible). I discovered something new today! We had horrible storms Friday night (I need a new roof) and we took the jeep for a spin to look at all of the houses and businesses that were blown down or severely damaged. I noticed clutch has to be fully on the floor to come out of gear but if you let the clutch out just a little it also improves the grinding. This clutch deal may be the beast that is causing problems! Still going to continue to experiment and get to the bottom of this. I will continue to update everyone as I discover stuff. Looks like my new transmission money is going to my deductible for now. :(
 
#18 ·
Update...
I have discovered I can almost completely get rid of grind on upshifts by waiting on engine RPM's to drop to 1100-1500. This has not helped any on down shifting. From what I am finding its a combination of synchronizers and clutch causing my problems.
 
#19 ·
Just as you have waited for the revs to come down on the upshift.. you can blip the throttle on the down shifts. Less strain on the syncros all the way around.
 
#22 ·
The synchros are probably bad as already mentioned. Changing the fluid will never hurt. My suggestion however would be to make double clutching a habit until you get it fixed.
 
#23 ·
I know that this is probably not the place to drop this question but here it goes....
Does anyone have or know anyone that has an ax5 laying around for sale? Not terribly concerned with condition as long as everything is there and housing is good. I am looking for a used one that I can rebuild with a kit and swap out for mine. This would be a great opportunity for me to learn more about my jeep and transmissions in general.
Thanks for any help!
 
#24 ·
Where are you located? I have an ax5 because my brother thought he got a lucky deal on an ax15 lol. I also have an extra ax15 laying around and a dodge 2.5l external slave bellhousing that goes on an ax15 that works on a jeep 2.5l.
 
#25 ·
I bought a ’95 YJ 4 cyl and second gear was just mildly grindy. Just the normal stuff for these AX5s. My ‘89 did the same thing many years ago when it had 10k miles on it. So I changed the fluid (old stuff looked like spicy mustard) because who knows how long it had been and replaced with new 75w-90 synthetic. Now 3rd is grinding - was not before. If I hold the clutch and count to 3 mississippi, there‘s no grind. Anything faster and it grinds. Any ideas? I was expecting new gear oil to be a good thing.
 
#26 ·
Welcome to the Forum, from Cave Creek AZ.
 
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