Auto transmission bucks while cold, but runs fine after vehicle warms up. . .

[wavingpine11]

Sounds good! If all else fails you can pull the trans cooler line off the rad and drain some fluid out that way. Overfilled is just as bad as underfilled. How over is it?

When in AWD, the jeep can still be a one tire fire, IE if one tire slips on one axle the other 3 stop, hence the ability to spin one tire. The tractive force is a lot higher with all 4 tires being powered compared to just 2 though. In 4x4 HI the rotation of front and rear driveshafts are locked together so you would have to spin one front tire and one rear tire.

If you are seriosuly getting wheelspin in full time 4x4, I would buy new tires, athough with the history of this rig it might just be your trans slipping

It has new-ish but ultra-cheap no-brand tires on it now, but I'll be switching them out for the BFG 235/75/15 AT's that are on my 92 this coming weekend, since that's off the road with power steering and clutch release issues for the winter. Wish I had a garage. . .

 

[lawsoncl]

The 87 tranny will not work with the transmission computer in the 98. The 98 computer is expecting to see a front input speed sensor which is not present on the older tranny. The pulse count per rev from the rear sensor is also different so even if you cobble the wires and don't hookup the front sensor it isn't going to upshift. Look for a 98 tranny. You can't just swap in the older trans computer either.

Instead of just draining off the excess, I would suggest pulling the pan and draining as much oil as possible, check the filte (really just a metal screen) and refill with Dexron III. If you have a multimeter, check the electrical resistance of the solenoids while you have the pan off.

 

[wavingpine11]

The 87 tranny will not work with the transmission computer in the 98. The 98 computer is expecting to see a front input speed sensor which is not present on the older tranny. The pulse count per rev from the rear sensor is also different so even if you cobble the wires and don't hookup the front sensor it isn't going to upshift. Look for a 98 tranny. You can't just swap in the older trans computer either.

Wish I would have known that earlier. Would I be able to swap it into my 92?

Instead of just draining off the excess, I would suggest pulling the pan and draining as much oil as possible, check the filte (really just a metal screen) and refill with Dexron III. If you have a multimeter, check the electrical resistance of the solenoids while you have the pan off.

Speaking to the solenoid, what would the typical resistance of this be in cold to subzero weather? I found a receipt for a transmission filter in the car after I bought it. I'm startig to think the previous owner replaced the filter, then re- (and over-) filled the transmission fluid, but that didn't fix his problem. So he gave up and sold it to me cheap.

So I'm beginning to think that my initial assessment of this problem is incorrect. I'm starting to think that the IAC valve is going bad. Here is my evidence: after having driven it a few times, I started to let it idle until it was warm. For the first minute or so, it idles fine. Then it begins to idle very roughly, almost as if it's going to stall, and it smells especially rich at this time. Then it surges upward in RPM's, smooths out, then the RPMs drop back down. If I wait for this cycle to finish, then there is no further drivability issue. Any time it needs to warm up, meaning sits more than a few minutes in between drives, then I need to allow it to warm up like this. If I don't, it'll buck and give me no smooth power transfer. I thought this was a transmission issue, but because I really doubt that the transmission is warming up at even close to the rate of the engine, and because it idles in a way that is reminiscent of the poor driving for that minute or so, I think it's an IAC issue. Anyone else think the symptoms may fit this diagnosis? I didn't have the tidbit of knowledge before that if you let it idle, idle poorly, then recover, that what I initially thought was a transmission problem ceases to occur.

 

[Slo-Sho]

And through all of this there are no trouble codes?

 

[wavingpine11]

No codes at all.

 

[Slo-Sho]

Sounds like the ECM is about to take a shat, soon the gauges will no longer register, then one morning it is just going to crank and crank. Enjoy the ride while you can!

 

[lawsoncl]

Speaking to the solenoid, what would the typical resistance of this be in cold to subzero weather?

11-16 ohms to ground I believe. Best to measure that at the transmission controller connector, so you check the wiring as well.

 

[wavingpine11]

Update: my check engine light works, but was not illuminated. I checked for codes and got 1. P0463 Fuel Level Sensor A high input. Sometimes the fuel gauge shows that the fuel tank is empty when I first turn the truck on, but then it creeps up to the correct level after a few minutes. Not sure if this is a related or unrelated factor, but it's certainly worth mentioning since I'm most likely dealing with a fuel, air, or transmission problem.

Anyone care to comment on my assertion that it is not likely the transmission given all the new information I've picked up?