[Hero]

So after a long battle with with no OD on my 42re I had a transmission shop “fix” it. I just picked it up Friday and drove two hours home. First gear seemed to hold a little long, but Overdrive worked again so I was happy. It was pretty much a full rebuild.

Today though we took it for a road trip and an intermittent previous issue reappeared. Driving down the canyon (about a 1500 ft elevation drop over 30 miles) it seemed like it went into neutral, at about 40mph after coasting into curves and then accelerating. Prior to having the rebuild when it happened I would run the shifter thru the gears and it would eventually have the 3 existing gears again. This time I realized 1st gear was the only gear working and at 40 mph the rpms were high and why it seemed like it was neutral but was actually 1st at too high of a speed. 1st was rebuilt and maybe why I could feel it this time. I stopped and turned the motor off to see if fluid was pouring out or something obvious. When I turned it on, everything shifted perfect, we put a 100 miles on it up the mountain and back down.

A quick google I found mention of OSS and realized the symptoms were the same as one time 6 months ago when I unhooked the sensor to test for overdrive issues.

This same issue happened a couple of times in the same canyon on the day I drove it to the transmission shop originally. It seems like on “coast” into a curve and then accelerate the transmission becomes confused and goes into OSS limp mode (not the real limp mode). There is also a chance that I have to brake in the curve when it happens, I remember being stuck behind a slow driver that was riding his brakes (I normally coast), which got me to wondering about the relationship of ABS and OSS. Wondering if a problem between them might make the PCM freak out?

I will call the transmission guy on Monday but was was wondering if anyone had heard of a similar irregularity? It obviously doesn’t happen everytime, but when it does happen it is sharing similar conditions. This is the third or fourth OSS sensor over two years and I put a new pigtail on when I inspected the wiring harness, but this would happen before the new pigtail too. I’ve even considered the weight shift of curves is making a wire shift and short.

Maybe it’s something the mechanic missed and will warranty, but if not, I really don’t want to give him more money for him to look for a nick in a wire. It’s already cost more than the original price of the Jeep.

 

[Hero]

The last sensor I installed in April was a Mopar. I don’t remember seeing one on the parts list for the repairs….so it’s probably still the same.

 

[Hero]

So the incident happened again on Sunday, this time on a straight highway. Still a “coast” to throttle situation. Stuck in first until I put it in neutral while rolling, turned motor off and restarted. All 4 gears returned.

Took it to transmission guy this morning, of course it couldn’t be replicated with the mechanic and his tablet didn’t notice anything. But he is keeping it to try and replicate.

Only codes were ABS for front wheels and “wrong tone ring” or something similar. I did have my own reader going and on a long downhill stretch I could see individual wheel speeds. Most of the time the speeds matched or were within 1 mph of each other but more than once I saw something like this:

Right Front 58mph
Left front. 58 mph
Right rear. 178mph
Left rear. 58mph

Then things would go back to normal, once I saw a 54mph drop in one wheel sensor.

 

[mpgmike]

I'd start looking at the obvious -- RR wheel sensor. Could be the toothed wheel is rusty and the flakes of rust are false-triggering pusles. Try looking at it, if it looks cruddy, at least hit it with a wire brush to get the worst off.

 

[Hero]

I'd start looking at the obvious -- RR wheel sensor. Could be the toothed wheel is rusty and the flakes of rust are false-triggering pusles. Try looking at it, if it looks cruddy, at least hit it with a wire brush to get the worst off.

So do you think the computer would react to the scenario with a transmission shutdown?

I’ve seen mixed reports in the JK and WK sections that they would have a limp mode caused by ABS, but everything I’m finding on WJ, people say it’s not smart enough.

 

[mpgmike]

I drive a '95 ZJ, so I have no experience there. I haven't seen other makes/models that react that way over a wheel sensor either. My best guess is no. It would seem more like a shift governor sensor or solenoid (or something like that).

 

[Hero]

I drive a '95 ZJ, so I have no experience there. I haven't seen other makes/models that react that way over a wheel sensor either. My best guess is no. It would seem more like a shift governor sensor or solenoid (or something like that).

I wish this guy would have gone into more detail about the Master Drive sensor.

 

[Hero]

To update all of my transmission posts:

Even though all signs kept pointing at electrical…a rebuilt valve body at this point has cured the mystery “limp mode” that shouldn’t exist.

After researching some GM transmission issues where “hot pressure” would open up cracks and cause pressure issues. I suspect that was the case somewhere in the valve body as it would be near 20 minutes from cold start, and if early was from being a short stop somewhere and then restarted in city traffic. There was some mention of many transmission shops testing cold pressures versus hot pressures, so giving my transmission guy the benefit of the doubt…maybe that’s why he missed it, although an actual rebuild would have probably caught it.

So electrical doesn’t necessarily mean electrical, sometimes it can be a mechanical issue behind there.

 

[Inspector Ratchet]

Yes, valve bodies can be intermittent hard to diagnose. A lot of trans rebuilders are not very thorough or knowledgeable when it comes to this. You are also correct that a DTC does not necessarily mean an electrical issue. It does control mechanical parts. The logic for the DTC to set looks at and assumes that the mechanical parts did their job. Many trans codes are based on pressure readings or speed sensor readings. They assume that the mechanical stuff did its job.