AW4 slipping in heat

[smokeyyank]

Howdy all, so I need some advice with my AW4. The issue at hand is when it's hot out, over 85*, and I've been driving over 55mph/2k rpm range for a while the tranny feels like it's slipping and there is a lose of power. There will be a lag and then the RPM's jump up. It does not happen all the time, just when I've been driving it for a while, 20 mins plus, in the heat. When going up a hill the problem seems to be more persistent. All other gears are fine it's only OD that seems to have the issue. Currently, it has a tranny cooler that bypasses the cooler connected to the radiator. It had the same issue before when ran through the radiator. I've been doing some research and a few people have mentioned that the TPS may be the culprit. A few months ago I had an issue where the jeep would not turn over. Would crank but not turn over. It sat for a few days went to go back and it fired right up and drove fine. Had also read that the TPS may be faulty. Any advice is appreciated.

 

[Tim_MN]

Are you really having transmission issues, or is there an issue with engine/PCM/sensors ? Take the same drive with the same +85° temperatures, only do it all in 3rd and not OD.

Since you mention previous undiagnosed issues, you should test some sensors (TPS, CTS, CPS), and consider an OBD-II scanner or Bluetooth app and monitor the engine.

 

[smokeyyank]

Are you really having transmission issues, or is there an issue with engine/PCM/sensors ? Take the same drive with the same +85° temperatures, only do it all in 3rd and not OD.

Since you mention previous undiagnosed issues, you should test some sensors (TPS, CTS, CPS), and consider an OBD-II scanner or Bluetooth app and monitor the engine.

No ODB, it's a 93. Should have put some more info in there. Have drove it in 3rd and it will still occasionally happen but not nearly the same as being in OD.

 

[dantheman!]

have you changed the fluid and verified all your cooler lines are in good shape?

i ask about the lines because one of mine was kinked causing mine to heat up on me.

 

[smokeyyank]

have you changed the fluid and verified all your cooler lines are in good shape?

i ask about the lines because one of mine was kinked causing mine to heat up on me.

I have changed the fluid (Used DEX/MERC) but have not gone in a done a full flush with filter and all. Was something I was going to try and do soon. Lines are good still just a little drippy in some spots.

 

[Demonoid369]

Maybe plumb in a temp sensor into the transmission lines to see what temp you are getting in the transmission. Have you verified your torque converter is locking up or possibly unlocking?

 

[smokeyyank]

Maybe plumb in a temp sensor into the transmission lines to see what temp you are getting in the transmission. Have you verified your torque converter is locking up or possibly unlocking?

This was another thing I was thinking it could be. How to I check that? Isn't it something with the brake pedal.

 

[Ecomike]

The starter ran free with out turning the flywheel? Or do you mean it did not start

"A few months ago I had an issue where the jeep would not turn over. Would crank but not turn over."

 

[Demonoid369]

This was another thing I was thinking it could be. How to I check that? Isn't it something with the brake pedal.

Ya the way I read is you have to be above 40 mph and as you have your right foot on the gas, quickly tap the brake pedal with your left foot and if the torque converter is locked, it should unlock and the Rpms jump up 200-250 Rpms then quickly drop back down. Do that in both over drive and 3rd

 

[cruiser54]

A drain and fill is all you need to do.

Ever adjust the Throttle valve cable which affects the line pressure applied to the clutches in the trans?

Takes 10 seconds to do:

https://www.youtube.com/watch?v=c0di1z5j1fU

 

[smokeyyank]

The starter ran free with out turning the flywheel? Or do you mean it did not start

"A few months ago I had an issue where the jeep would not turn over. Would crank but not turn over."

It did not start, would crank but would not turn over.

 

[cruiser54]

It did not start, would crank but would not turn over.

That's called Crank-No start just for clarification.

 

[smokeyyank]

A drain and fill is all you need to do.

Ever adjust the Throttle valve cable which affects the line pressure applied to the clutches in the trans?

Takes 10 seconds to do:

https://www.youtube.com/watch?v=c0di1z5j1fU

I think I'll start with this and see. I haven't adjusted the TV cable on my XJ but did it on my K5. At least then it was apparent through all the gears hadn't thought of it now because it's only under those certain conditions. But easy enough to check.

 

[Ecomike]

That's called Crank-No start just for clarification.

For even further clarification "cranks but would not turn over. " tells me the starter works and spins but the engine does not crank, rotate and the starter is thus not engaging and rotating the engine crankshaft.

 

[smokeyyank]

Alright, did a flush and filter. Ton's of nasty black junk at the bottom of the pan. 3 cans of brake cleaner later it was nice and sparkly. Well at least Jeep sparkly. Drove it around and seems to be fine. Going to drive it to work this week and put it through some traffic to see how it reacts. Also added in a new 97+ aux fan. Hoping the tranny flush is the only issue because I'm itching to go wheelin this weekend!

 

[Ecomike]

What did you use brake cleaner on????

 

[smokeyyank]

What did you use brake cleaner on????

The bottom of the pan the clean it.....