Archived transmission help!

[Grinder1]

Hi guys, got a problem here. Need my truck back ASAP for work.



Well I finally decided to have my trans rebuilt on the 95. Upgraded the converter, transgo shift kit, etc. but did not go crazy on it, as I'm not putting out any serious HP. The shop called and said there's an electrical problem, won't stay in 4th and converter won't stay locked. In the past when that happened I replaced the trans temp sender, end of problem. Per my request, they replaced sensor, no help. The shop owner thought maybe the alternator output was creating interference to the ECM. I know that the TPS can also cause problems, it was replaced about 60k miles ago.



I am going down to the trans shop today to road test my truck, as it was not acting up before they tore into it (it did have one 3-4 shift hiccup a few weeks ago). I'm trying to think of what component they replaced/modified that would cause this problem. Could a bad valve body rebuild cause this? Any suggestions on what to look for would be greatly appreciated.

 

[Bob4x4]

The trans shop is supposed to be able to tell you what's wrong not vice versa. If it was not doing it when it went in they need to take care of it. Any decent trans guy would drive the truck before pulling it and should have told you at that point if they could not fix it

 

[DavidC]

The trans shop is supposed to be able to tell you what's wrong not vice versa. If it was not doing it when it went in they need to take care of it. Any decent trans guy would drive the truck before pulling it and should have told you at that point if they could not fix it

There in lies the problem. Everyday it is getting harder and harder to find competent shops. The Wife took her Toyota to the dealership for a front end alignment and they called with doom and gloom. One was the front brakes are down to the metal and the rotors are ruined but we can fix the front brakes for 580. 00 . After she came home I checked the brakes myself and there was at least 10k of pad left. Sorry for the hi-jack.

Dave

 

[Grinder1]

The trans shop is supposed to be able to tell you what's wrong not vice versa. If it was not doing it when it went in they need to take care of it. Any decent trans guy would drive the truck before pulling it and should have told you at that point if they could not fix it

Hi Bob. Yeah I totally agree with you. I went to the shop today and they are going to make it right. They replaced the TCC and Overdrive solenoid pack/wiring loom as part of the rebuild, and now we are all pretty convinced that the new part is faulty. The problem is definitely electrical, and that is the only component that was changed. They are going to replace with another new part tomorrow, on their dime. If that doesn't fix it, either the wiring harness got damaged during the R&R or the PCM went south on me. It would just be my luck that Mr. Murphy was in the new part box. I do need to hit the books tonight and see if they overlooked something else.

I road tested truck and everything else seems fine. Good shift points, just a tad firmer than before. Converter is a little tighter, but I may want to go with an even a lower stall. Got any thoughts on that?

 

[fox]

It can be the TPS or brake switch bouncing.

 

[Bob4x4]

The shop should test drive the truck monitoring the inputs to the PCM that are trans related. With a drb it is very easy there is a trans specific page that will show the info needed

 

[p-Bar]

The shop should test drive the truck monitoring the inputs to the PCM that are trans related. With a drb it is very easy there is a trans specific page that will show the info needed

And everybody has a buddy with a DRB:-laf

 

[Grinder1]

Yeah the ol' trusty DRB scan tool... ... wish I could get a hold of one. Unfortunately this transmission shop does not have one either. There's an electrical guy nearby that does. May have to pay him a visit.
The wife wants to keep "Rambo" in the family for a long time. I'm gonna put a DRB tool on my Christmas list. How much do they set you back?

 

[Grinder1]

It can be the TPS or brake switch bouncing.

I thought about that Fox, but why was it fine before transmission rebuild? Only thing I can think of is that the Borg Warner replacement isn't the right spec, and is throwing the PCM a curve ball. What other sensors that input data to the PCM are mounted on the trans? Speed sensor? Would be completely stupid if they forgot to hook up/check a connection.

 

[Grinder1]

No OD, no TCC lockup

Geez what a PITA this trans rebuild project has become

Transmission tech was unable to clear codes so took truck to Dodge dealership per my request. Dealer kept it for almost 2 days, and did nothing because they didn't have the proper cable to hook it up to their test equipment #@$%! Are you kidding me? This is when you wish you had a '96 with the OBD 2 plug. Now it's at an auto electrical repair shop. Tech was able to get trans to shift properly by resetting the codes. He checked all the PCM perimeters and found no problems. Road tested again and thought we had the "gremlin" out of the PCM, and out of the blue it went back to not wanting to go into 4th or converter locking. One theory the shop has is that by using the manual TCC lock/unlock switch (which will set off code 37, always has), that the PCM is losing the logic for the transmission. I told tech that I have had that switch in truck since 1998, never an issue. The only electrical part that was replaced in trans was the solenoid pack (Borg Warner part)for TCC and OD. I can get the converter to lock with my "mystery switch", so we know the TCC solenoid is working. Get road speed up to approx 60mph and it will go into 4th/OD, so the OD solenoid is working.



Could try replacing the PCM at a good guy price of about $400 plus $125 core, but hate to just throw parts at the problem without knowing for sure. Anyone out there had this problem? REALLY need some tech help on this pronto. Sorry for the long rant.

 

[fest3er]

It may be that the PCM doesn't think the vehicle is moving. Have you/they verified the vehicle speed feed into the PCM? In '98, they changed it to feed it all from the rear axle sensor. Earlier years, there was a feed off the trans. One or t'other might not be working right.

 

[cerberusiam]

There are 3 sensors that contribute to the PCM for OD and lockup, VSS, temp sensor, and TPS.

Have you validated TPS readings are in range and stay that way when warm? You could bypass it with a linear taper to test.

Temp sensor is good? IIRC, just a jumper wire on the plug will bypass it.

Have you replaced the VSS? The will go bad inside and send a signal that will cause intermittent OD but speedo still works.

What codes are showing and what do they mean?

 

[Grinder1]

It may be that the PCM doesn't think the vehicle is moving. Have you/they verified the vehicle speed feed into the PCM? In '98, they changed it to feed it all from the rear axle sensor. Earlier years, there was a feed off the trans. One or t'other might not be working right.

Thanks Neal. According to the tech, VSS is working. Is the PCM using that feed correctly, don't know as of yet. I have the feeling that the PCM will need to be replaced. How far can one go on the diagnosis when the program logic is proprietary? Would be great to hear from someone who knows the diagnostic tools (ie. DRB scanner, Genesis, Snap-On), and could enlighten me on what exactly tells us the PCM is faulty.

 

[Grinder1]

There are 3 sensors that contribute to the PCM for OD and lockup, VSS, temp sensor, and TPS.



Have you validated TPS readings are in range and stay that way when warm? You could bypass it with a linear taper to test.



Temp sensor is good? IIRC, just a jumper wire on the plug will bypass it.



Have you replaced the VSS? The will go bad inside and send a signal that will cause intermittent OD but speedo still works.



What codes are showing and what do they mean?

Thanks for that info. You are correct on the input data that contributes to OD/TCC lockup. TPS shows good, temp sensor has been replaced. VSS, that's something I'm going to have to look into further. Are you sure about speedo working but signal to PCM goes bad? The trouble codes that I got off the truck using the self diagnosis were 37 and 45. 37 is the TCC. Anytime you use the TCC mystery switch the 37 code will set. Never been a problem. The 45 is the OD solenoid circuit. Why or where the problem is no one can figure out as of yet.

 

[cerberusiam]

The 37 code is probably being set because the PCM is seeing a dead short on that circuit. You don't have a resistor between the switch and ground do you?



The VSS problem is a constant issue on the 1st gens and I am pretty sure the PCM on the 95's are not a whole lot more complicated than the 92-93 modules. The drivers for the speedo signal and lockup\OD controls are different. The speedo and odometer will still drive even with a VSS signal that will cause the OD to go crazy.



Does OD and lockup start working every time you clear the codes? Can you replicate the failure by using the lockup switch?



Have you back checked the trans control harness to see if it is rubbed or bared anywhere?

 

[fest3er]

First, get the service manual and find out which circuits are involved and which components are involved. Then find each end of the wires or pairs. This particular problem involves a regularly-varying signal (AC-like). For that, all you need is a normal, ordinary oscilloscope; an old 20MHz model is more than adequate.

Jack the drive wheels safely off the ground, start engine, put it in gear. Connect the scope probe to the sensor; ensure it is producing what appears to be a 'sane' signal. Then connect to the other end of that wire pair and ensure the signal reaches the other end. Then check the near end of the next wire(s) in the path, then the far end. And keep going 'til you reach the PCM. If you see a good, solid, sane signal reaching the PCM, you know the VSS signal is good all the way. Put the probes on the PCM trans control lines and see if they react to vehicle speed the way they should. The results at each step may provide clues.

To use my '98 12V for example, I would connect a scope probe to the sensor at the rear axle. At 5MPH, I would expect to see a regular, wide-ish and square-ish pulse of about 600mV amplitude. As the speed increases, the pulse will narrow and the voltage will increase to 2. 5V or more. I would expect to see nearly the same signal at the CAB (controller, antilock brake) because it's effectively a differential signal across twisted pair wiring. Between the CAB and the PCM, I would expect to see a solid 2. 5-5V signal; the CAB converts the raw sensor signal to a solid TTL-ish variable-width pulse that's easy for the PCM to read.

Your earlier model probably has the rear end sensor feeding the CAB and the trans feeding the PCM.

If you get good signals all the way and the TPS works right (squirt some contact cleaner in and work it a bit to clean the 'wiper' inside) about the only thing left to check are the various ground connections. Measure the voltage between the battery NEG post and various points away on the chassis and trans, including the NEG cable connector at the battery. Up to ¼ volt, I wouldn't worry. ¼-2 volts, I'd be suspicious and would want to find the dicey ground strap. Over 2 volts, shut it down and redo *every* ground point, because on a vehicle that age, if one is bad, you can guarantee that more are or will soon be bad. Connect a jumper cable between the battery NEG and parts in question (and temporarily secure it in place). If that makes a difference, you *know* it's a ground problem.

Then go through and ensure that you have proper voltage everywhere it's supposed to be (with respect to trans control).

As these trucks get older, they start to do weird stuff. I bought a replacement CAB years ago (dealer, right numbers, etc. ) The dealer's tool could never set the defaults in the CAB; the ABS light's been blinking for at least 8 years. And when I turn the key on and/or start the engine, the speedo jumps to max range, then eases back to zero; dunno why, maybe it's the tru-speed unit. Last year, the engine/trans would 'shudder' now and again, as though the TC clutch was momentarily releasing or two normally mutually exclusive things in the trans were engaging at the same time; maybe it was a bit of spline letting go. In late October, the input splines on the trans gave up. I might get the truck back Wed. ; it was a long winter riding the motorbike.

Good luck. Hope you find the guilty part!

 

[Grinder1]

Well guys the nightmare continues with this 47RH trans rebuild. We are now into week 4 of the job #@$%!. The guy who's gonna be crying at the end of all of this will be the builder, not me. I'm sure he completely hates my truck by now. Electrical repair shop thought for sure it was the PCM, after they spent a week testing the dodo out of everything else. They ordered a factory rebuilt unit, installed it, and tested it for proper signal and voltages. All showed proper and within spec. Unfortunately the road test came up the same, no 4th gear or TCC lockup. Pretty obvious now that it's in the trans, which is what I have thought all along.

Now the trans shop has ordered a valve body, another Transgo Shift Kit, and a Mopar solenoid pack. They hope to have it all installed tomorrow. If they can't get it right after that, any suggestions?

 

[JHumphries]

Well guys the nightmare continues with this 47RH trans rebuild. We are now into week 4 of the job #@$%!. The guy who's gonna be crying at the end of all of this will be the builder, not me. I'm sure he completely hates my truck by now. Electrical repair shop thought for sure it was the PCM, after they spent a week testing the dodo out of everything else. They ordered a factory rebuilt unit, installed it, and tested it for proper signal and voltages. All showed proper and within spec. Unfortunately the road test came up the same, no 4th gear or TCC lockup. Pretty obvious now that it's in the trans, which is what I have thought all along.
Now the trans shop has ordered a valve body, another Transgo Shift Kit, and a Mopar solenoid pack. They hope to have it all installed tomorrow. If they can't get it right after that, any suggestions?

Have the order a whole transmission?

 

[cerberusiam]

Have the check the OD clutch pack lip seal very carefully. A 1/4 inch missing or the seal rolled will cause all your problems with OD and lockup.