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TC crapped out

Ice RHD

NAXJA Forum User
Location
NH
I recently brought my 2000 xj to a recomended tranny shop because of code po740 the pulled the pan and said there was a lot of clutch material and discolored fluid.

It shifted fine throughout but was slipping randomly at 55-60 on the way to the shop.

They recomend a rebuild or remanufactured install costing 2700 to 3000 (I bought the jeep for 4500 Which I knew I was overpaying for). They said the clutch material could be from the friction plates and junk spread though the whole tranny. I don't know about that?

I countered with replace TC and flush or pull inspect and replace TC or install used transmission.

Any experience or opinions greatly appreciated.

This shop was recomended to me but I feel backed into a corner. But I guess thats how it goes.
 
I have an uncle who works with salvage yards I am going to call him and get a price.

I would like one with a warrante.
 
Oh and they said they got a tps code also. Any relation to code po740?
Since this is an electronically controlled tranny, I'd go through any code-setting problems first. Early versions were controlled directly through a double TPS, and later ones get the TPS signal through the engine computer, but they all depend on this signal to work right.

Even if it doesn't solve the problem it might contribute, so I'd do it first.
 
Do a TPS first and adjust the TV cable.
 
Do a TPS first and adjust the TV cable.

Yes. On the earlier XJs the TCU was separate from the PCM, and one of the quick checks would be to unplug the TCU, or pull its fuse, and drive the vehicle shifting manually to determine if the problem is electrical in nature, such as tc unlocking or solenoids not operating correctly.

I hope there is a way to do the same test in the later models, but I don't know what it is.

ALL automatic transmissions (I like to call them slush boxes :laugh3:) will have some clutch material in the pan, that is normal.
 
Yes. On the earlier XJs the TCU was separate from the PCM, and one of the quick checks would be to unplug the TCU, or pull its fuse, and drive the vehicle shifting manually to determine if the problem is electrical in nature, such as tc unlocking or solenoids not operating correctly.

I hope there is a way to do the same test in the later models, but I don't know what it is.

ALL automatic transmissions (I like to call them slush boxes :laugh3:) will have some clutch material in the pan, that is normal.

The TCU was always separate. On the later models, it just moved to the drivers side above the gas pedal somewhere. Unplug it and shift manually with the stick. Have a look at http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html and measure the solenoid resistance. It might be a bad TPS or bad solenoid, which you can replace without dropping the tranny. The P0740 is bad t/c circuit, which would also point to a bad lockup solenoid. I posted a FAQ not too long ago with a part number and source for new solenoids.
 
The TCU was always separate. On the later models, it just moved to the drivers side above the gas pedal somewhere. Unplug it and shift manually with the stick. Have a look at http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html and measure the solenoid resistance. It might be a bad TPS or bad solenoid, which you can replace without dropping the tranny. The P0740 is bad t/c circuit, which would also point to a bad lockup solenoid. I posted a FAQ not too long ago with a part number and source for new solenoids.

Thanks for correcting my comment on the TCU. Old dog, new tricks.
 
It seems to be a common misconception that Chryco rolled the TCU function into the engine computer. I think they did on Grand and Wrangler as those use Chrysler autos.
 
It seems to be a common misconception that Chryco rolled the TCU function into the engine computer. I think they did on Grand and Wrangler as those use Chrysler autos.
They did not roll the TCU function on to the computer, but they did roll the TPS interpretation and calibration onto it instead of running a stacked TPS, as Renix systems have.
 
I talked to them again today and phone answering guy said " I talked to the owner and he said with the amount of clutch material and the coloration of the fluid I highly doubt that just changing the TC and flushing will fix it. We can do that if you insist but it not our responsibility if that doesn't fix it." So I said whatever I'll talk to you later.

So I called scrapyard and got a deal on a used tranny. Cheaper than what a new TC would cost. So I think I am going to go that route. Then maybe rebuild the one I take out of my xj.
 
They did not roll the TCU function on to the computer, but they did roll the TPS interpretation and calibration onto it instead of running a stacked TPS, as Renix systems have.

That was one thing that Chryco got right. They went to Aisin-Warner and had them change the TCU to accept the same range (0->5 volts) that the engine computer expected. Then they just feed it the same signal from the TPS. There were a few other things Chrysler cleaned up in the design along the way such as well such making the auto tranny output spline count the same as the manual. Moving to the OBDI electronics was a nice improvement as well.
 
That was one thing that Chryco got right. They went to Aisin-Warner and had them change the TCU to accept the same range (0->5 volts) that the engine computer expected. Then they just feed it the same signal from the TPS. There were a few other things Chrysler cleaned up in the design along the way such as well such making the auto tranny output spline count the same as the manual. Moving to the OBDI electronics was a nice improvement as well.
Interesting. I always thought (probably just assuming) that the Aisin TCU remained the same, and that the Chrysler PCU reinterpreted the data and sent it in the same form as before. A moot point for those of us who are addicted to AX-15's, but a serious difference if you're junkyard shopping for a TCU.
 
I remember seeing someone post that as well. Looking at the wiring schematic, the signal comes straight off the TPS on the later models. So yes, you need to get the right TCU which is easy since they are color coded. The Renix era ones have a grey connector and the OBDI ones have a green connector. The connector changed altogether in 96 or 97 I think. The wiring harness and connector have little tabs to prevent you from connecting the wrong one, but you can get them to fit with an exacto knife. I recall a thread about a guy who did that and wondered why it wouldn't shift right - swapping to a renix tcu fixed it.
 
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