Need HELP with shifting problem

[Tibusaki]

1046976

I have a 1990 Jeep Cherokee Limited Automatic with a 4.0L engine. My jeep shifts through all the gears at 4500 rpm except for the last gear at almost 5000 rpm!!! I verified my transmission fluid and it was black, so I changed my fluid and 2 weeks later is was black again and the problem was not resolved. I called for a transmission kit but found a good transmission that is fully functional at a lower cost. So now I have a new transmission and I still have the main problem which is it shifts at high rpm only!!! What else can it be? I tried the pulling the cable on the throttle that goes to the transmission on my lift while my friend was accelerating and still shifts at high rpm! So, what else can it be???

[addsig]

 

[Kevin72]

1046997

That throttle valve cable has to be adjusted very precisely. If not, the pressures inside the valve body will be off, and you could burn up the transmission. Pick up a Haynes manual - the adjustment procedure is in there.



If you've already done that correctly, check the things that existed with both transmissions, like the torque converter and transfer case, and look for any leaks.



Good luck, and let us know how you fix it.[addsig]

 

[MudderChuck]

1047069

The advice about checking the throttle valve (kick down) cable is good advice. A plugged cooler, can also cause problems, blow backwards with a rubber hose (not to much pressure). Somthing to also try is put the rearend up on jack stands, at a slow RPM shift a couple of times from drive to reverse (gently). Put it on the ground and take it immediatly for a test drive. If there is a partial plug in the valve body this will sometimes dislodge it, at the least if your shift points change you´ll know it was probably something in the valve body. Varnish from burnt transmission fluid can really gum things up.



I´ve never messed with the electrical for a Jeep transmission (GM?). The engine temp. has a bearing on the pump pressures and shift points, But 2000 RPM over the normal shift point doesn´t sound like this is the problem.



Sounds like gummed up valve body, possible internally leaky converter or slipping clutches. Check out a good manual and see what they have to say. And don´t forget the easy stuff, like oil levels and the right dip stick.[addsig]

 

[Tibusaki]

1047077

Thanks guys for your advice. I already tried the advice concerning to jack up the rear and at low rpm to shift from reverse to drive. It did not change anything. today, I will check the rest what you guys said and will keep you posted when I'll have an update.

Thanks again![addsig]