AX15 synchros possibly out, Thoughts?

[Mud_Dog]

Heya guys!
I have a 95 XJ with an AX15 & stock 3.08's.

Over the past few months, my tranny has been consistently grinding between 3rd & 4th gear. I have tried double pumping the clutch, changing the fluid out(Penzoil synchromesh), checking & topping off the clutch cylinder fluid. There were signs of copper flakes in the fluid when I changed it which tells me its gotta be synchro... Problem is, I've never changed out synchros in a tranny before & have NO idea what I'd be getting into.. That, & I also have no idea how you can guage how worn your clutch is on a hydraulic system. Is it possible my clutch plate is just wearing out? The Jeep does jerk foreward slightly when I put it in first, & grinds in reverse if I don't wait a moment with the clutch engaged.. ANY THOUGHTS OR ADVICE IS GREATLY APPRECIATED!!

[Guest]

I am going to guess that you have the wrong fluid in the transmission.
I use redline MTL-1, Easier shifts when cold, quieter than 10w-40 or the Oreillys house brand.

And reverse is not synchronized, I drop it into 4th then to reverse or just let the clutch out and grind a bit into gear.

This link will help when/if you rebuild it http://www.billhughes.com/temp/AX15.pdf

And here is a bit from the research i have done:

I switched to redline MT-90 (full synthetic, very best stuff on the market) and the problem went almost away completely. Amsoil is the best. I've read a HUGE study on it on the intarwebs and it consistently performs better than both and at a cheaper price than redline.

Do not put syncromesh or Syncromax fluids in the AX tranny. Those fluids are for the later NV3550 & NSG 6 speeds. Redline MT-90 or Amsoil MTG, SVG can be used also. The SVG is a GL-5, but being synthetic it will not harm the syncros. Your choice, all 3 are good.

Will any SAE 75W-90 GL-5 oil work? No. You need to look for a GL-4 75W-90, Unless it has been engineered to not harm the yellow metals. The Amsoil is GL-5's are OK with yellow metals. I cannot speak for other brands. You need to check with the oil maker to verify.

Yellow metals = brass & bronze which contain copper.
Copper based alloys do not like acidic environments. GL-5 gear oils Can contain EP (extreme pressure) sulfur based additives which may increase the acidity of the oil especially at high temps when the additives tend to break down releasing sulfur and forming sulfuric acid.
Saying this I would like to also say that it takes alot of heat to cause the additive breakdown. Most transmissions do not see extended periods of high temps in daily driver jeeps.

[Mud_Dog]

hmmm, interesting. I've been doing a bunch of research as well & it seems like there is no real definite answer on the TRUE recommended tranny fluid. The book calls for GL-5, but GL-5 has been proven to destroy the alloy of synchros so another HUGE group of websites & people say GL-4 Redline MT-90, which is what I had in my last Jeep.. this sucks tho, cuz it grinds like theres absolutely NO synchronization between 2nd to 3rd, 3rd to 4th, & MAJOR grinding from 4th back to 3rd.... dammit... I cant afford tranny work man.. lol

[spunebil]

Match rpm to gear selection and you can "float" gears ! But even with a synchro trans, if rpm is way off, you will grind ! And its double clutch, not double pump ! I can dbl cltch and also float gears in any manual tranny, it didnt seem important that much when driving 18 wheelers over the road, but has been great to know since then ! :)

[reward_1000]

If it were clutch issues it would grind between every gear, not just a specific gear. With copper colored flakes in the oil then yes you have synchros wearing. If it were the wrong fluid issue again it would be all gears. Sounds like it is time to pop the trans and check it out. The clutch disc will have rivets on it like some brake shoes and pads. You can tell how worn the disc is by the how much material is left above the rivet head. I have never done synchros in one but they can't be that hard.

[Guest]

If you can rebuild a carburetor, you can rebuild a transmission.

As far as replacing the syncros , You'll probably want a gear puller. I never got that far, A main cluster costs more than a used AX15.

[Mud_Dog]

lol good to know. Thanks guys! I'll be checking into it more this weekend. Replacing synchros wouldn't be hard, but the hard part is that I'm currently living in a duplex with no garage, PLUS I had a big portion of my tools stolen at Pickn pull a few weeks back :( needless to say, my options are really limited right now..

[Mud_Dog]

I gotcha. Well, by chance, do you know of anyone selling an ax15? I'm having a hard time finding one

[Mud_Dog]

Match rpm to gear selection and you can "float" gears ! But even with a synchro trans, if rpm is way off, you will grind ! And its double clutch, not double pump ! I can dbl cltch and also float gears in any manual tranny, it didnt seem important that much when driving 18 wheelers over the road, but has been great to know since then ! :)

OOps, haha. not sure why I said double pump, but heyyy!! Well, I double clutch with all my manuals and yes it definitely makes for a smoother ride. This tranny however, it doesn't make a difference in the grind, not sure why...

[mujeeper]

I would bet it's your synchros, but might not be that bad to have a mechanic take a look so you don't go through all the work & have something else break down the road that you could have easily fixed when you had it all taken apart. Hear me out, first.

First time my tranny went out it was the synchros. I contacted a guy who rebuilds them on the cheap, picked up the rebuilt, & gave him the old. Refilled with MT90 (since I had heard about the incorrectly specced GL5 at that time). All was well.

Several years later I had more issues. Now, more mechanically inclined & a garage with tools at my hands, I decided to give it a shot. I pulled the tranny out, opened it up.....then decided to rethink my strategy. I contacted a transmission shop (I think it was A&V or AEV transmission, west of I35 in Lenexa (I recommended them in a previous post so can look that up if needed). I took the tranny up to him, he looked it over & it was a few bad seals, broken 3rd & 4th gears, & a few other minor things & was good to go. The fix was less than 300 & I suspected that it was more of a "side job" so I paid in cash. I reinstalled the tranny & now using penzoil syncromesh (good price, readily available & is recommended for brass synchro ring trannies). Been working fine ever since.

Pulling a transmission isn't all that difficult & can be done in a day if bolts cooperate & you have the tools needed. If my transmission acts up again, I'll probably go to the same transmission mechanic & remove & install the tranny myself. I'm sure I saved a lot of $$$ pulling it myself. From there, the experts who know all about trannies peak in & replace on whatever needs to be worked on & might catch things that I'd miss.

While you have it out I recommend resurfacing/inspecting your flywheel & inspecting your clutch. Might be worth the exttra labor now pending the mileage on those components already.

Oh, lastly, everything above was from a 95YJ 5 spd so you're probably dealing with something very similar to mine.

[Mud_Dog]

That definitely sounds similar to my problem. Although now, I'm quite sure its the syncro mesh that's going bad. If I had a place to work & a spare vehicle to drive, it'd make these issues not difficult at all lol
but I'll definitely check into that Tranny shop! I live just a few blocks away from it. Thank you again for the input! It helps allot!

[RoKn]

In respect to the fluid, I run mobile1 synthetic 10w30 motor oil in mine.


Have now for the past 2years, seems to shift cleaner then before, no issues since, and I wheel/beat the snot outta mine.


I thought my transmission was going out at the time, similar issues to yours although the fluid was so dirty I couldn't tell if there were any metal in it.


RoKn