Problems shifting ax-15

[Menzenski]

I have a 1990 Cherokee (base trim level) with 4x4, 4.0 and a five-speed (which should be the ax-15, if I'm not mistaken). The transmission's been doing some funny things, and I'm hoping that it can be fixed without replacing it.

- When I start the engine and shift into reverse, there's a grinding sound like the clutch isn't disengaging, but the pedal is all the way to the floor. I've only noticed this right after a cold start; when the engine's warm, it doesn't seem to be a problem.

- 90 per cent of the time, the shifter won't go into any forward gear when the Jeep is at rest, which sucks because that means I can't put it in neutral at a red light. Usually I can get it to go into a forward gear by backing up, and shifting into first while still rolling backwards. This might just be co-incidence, but there was one day when I could consistently put it into a forward gear while stopped, and that day was noticably colder than most others.

- Shifting generally requires lots of force (both up- and down-, although up- is worse). Shifting into second and fourth especially, I really need to yank on the lever to get it into gear. I can usually get a smoother shift by staying lightly on the accelerator during the shift.

Any idea what these problems might be caused by? In the searching I did before starting this topic, I saw "synchromesh" and "slave cylinder" a lot, but I know next to nothing about transmissions. Thanks in advance for any responses.

 

[outlander]

First I would check the fluid level...but it really sounds like your clutch isn't disengaging all the way.There have been alot of post about the early internal slave(which yours should be,IIRC)taking a dump,That's why alot of people,like myself, do the external slave conversion.Not to mention ease of replacement.

Oh,one more thing before shifting into reverse try pushing the clutch in and counting to 5 before trying to go into reverse,this allows the gears to match speeds because reverse is not synchronized.

 

[Zoro]

I've also got a 1990 Cherokee with the same drivetrain as yours. Always on cold days I have trouble going into 2nd and sometimes 4th if it's really cold. Reverse always grinds on mine as well if you don't do the count to 5 thing.

Check your clutch fluid(if that's what it's called) there's a little black cap that says add only DOT brake fluid and this is next to the brake booster. For some reason my tranny acts up when the fluid is at full or anywhere below so a mechanic friend told me to fill all the way to the top and this seems to be working.

Good luck w/it

 

[outlander]

oops forgot to mention the part about checking the master cylinder level,thanks Zoro

 

[summitlt]

My reverse grinds too, its because the piolot bushing is dry, next time you want reverse, stop, put it in first, then goto reverse, grind free.

 

[otto]

My reverse grinds too, its because the piolot bushing is dry, next time you want reverse, stop, put it in first, then goto reverse, grind free

Works for my 1990 too. You might try changing the tranny gear oil for RedLine MTF or 75W/90. I changed to the latter last month and the AX-15 has never shifted so smoothly, regardless of outside temp. AX-15 takes just over 3 quarts.

 

[RichP]

Yea, fluid can have an effect, the AX15 is cold blooded enough as it comes from the factory with new gear oil, I changed mine about 4 or 5 years ago to Mobil-1 gear oil and it's been fine ever since thru two changes of lube. I'm about out of the case of gearlube I bought back then and the new stuff says GL5 on the bottle so I'm staying away from the newer stuff, going to order either the Redline stuff for the spring maintenance I do.
The Mobil-1 gear oil in the tranny and the Mobil-1 ATF in the transfer case sure smoothed things out though, especially in cold weather.

 

[87manche]

I too have heard good things about the Redline MT-90 oil. When I get a new tranny I'll be giving that a try.

 

[rumblebelly]

Yea, fluid can have an effect, the AX15 is cold blooded enough as it comes from the factory with new gear oil, I changed mine about 4 or 5 years ago to Mobil-1 gear oil and it's been fine ever since thru two changes of lube. I'm about out of the case of gearlube I bought back then and the new stuff says GL5 on the bottle so I'm staying away from the newer stuff, going to order either the Redline stuff for the spring maintenance I do.
The Mobil-1 gear oil in the tranny and the Mobil-1 ATF in the transfer case sure smoothed things out though, especially in cold weather.

+1. My old 88 XJ had the manual tranny and when it was cold it was a real pain to shift. I drained the fluid and added Mobile 1. It felt like a totally different tranny and cold weather didn't affect it at all.

 

[96XJcherokee]

shift into 4th and then reverse...you will avoid the grinding

 

[bajacalal]

Mambeu, your experience sound pretty typical of what happens when the hydraulic components of the clutch need to be replaced. They just don't seem to last that long or maybe I don't use the brakes that much in comparison. I would try checking the fluid level and then bleeding the system. And change the trans fluid, I have also had good experiences with Red line MT-90 and a pint of that LubeGuard gear fluid supplement in for good measure, shifts like a knife through butter. If this doesn't solve the problem, you probably need to replace the hydraulic slave or master (probably good to do both and the hose too).

Shifting from a forward gear to reverse helps. I don't know if this is because the ax-15 uses a straight cut reverse gear or unsynchronized gear or what but it seems to help with a lot of trannies that have the same R under 5 pattern.