I just bought a stock '92 Cummins with an automatic transmission. I am new to these trucks so I do not know what is normal and what I should be looking into. Well here is what is happening. When I start the truck cold meaning it hasnt run since the day before and I put it in drive or reverse the truck is REAL slow to respond. The engine revs up, but the truck does not seem to want to move and then it slowly begins to move and then finally everything is normal. All of this happens within 200 ft. or so. Are these trucks just slow to start while the transmission is warming up or should I be concerned with this?? Then finally while I am driving at about 50 or 55 mph the transmission begins fishing for its gear. It will not settle into one gear. It is trying to shift into Overdrive but just cant do it smoothly. You have to let off the accelerator and kinda fiddle with it until it will finally shift into the higher gear and then sometimes it will still downshift and you have to mess with it again. Anyway I am about to do some pump mods on this truck as I have just got all the gauges and stuff, but I didnt want to do anything to the truck until I knew the transmission was ok. What do you guys think is the problem and what can i do to check it out or fix it. Thanks again in advance for your help.

-Chad-

 

Chad, It sounds to me( and i am FAR from very knowledgable about trannys) that you may have two seperate issues there.
If the tranny is low on fluid or has the wrong fluid it, or if teh TC is going out, that could cause the hesitancy to go into gear when cold. how long are you letting it run before putting it in gear? i have a 93 auto, and it is "finicky" if I start it and immediatly throw it in gear, but if i wait about 4 seconds( which lets teh oil pressure come up in teh engine) it is fine.

The searching for OD could be a maladjusted TPS or a bad OD switch on the tranny. Look in the sticky for info on both the OD switch and checking the TPS..

But as stated, i am not an expert on this subject, I am sure some of the others who know more will pitch in here soon...

 

If You're in the truck while it's warming up try shifting the tranny out of park and into Neutral. I remember reading something here about the pump not pumping fluid through the torque converter whilst in park but it will in neutral.

I'm like Chris, I'm no tranny expert either. But it's something simple to try before you shell out the cash for an aftermarket torque converter!

And I agree with Chris on the TPS may be the culprit behind your OD problems.

Good luck!

 

I'd say a sticky regulator valve and a TPS that needs cleaned... Get 2 bottles of red lubegard, some ATF+4, do a flush/filter change and clean your TPS... The other guys were right, if you have a tired trans, the torque converter drains back on the stock trannies, idling in neutral helps this. A transgo tfod-diesel shift kit and a torque converter will do the truck wonders!

 

Murf Is right. THe A518 and the 727 tranny does not pump fluid to the torque converter while in park unless the valve body has been modified. If the truck sits for a few days, it will be a little slow on the inital take off if you don't warm it up in nuetral.

The throttle position sensor is a potentiometer that sits on a bracket on top of the injector pump. The wire in the middle of the plug is the output to the PCM. This tells the PCM when to allow the solenoid valve in the tranny to shift into overdrive. The initial voltage with the key on and the engine not running should be one volt. The voltage should smoothly increase as the throttle is moved to full fuel. If it doesn't, the TPS needs cleaning or replacing. If that isn't the problem check the temperature switch in the cooling line from the trannsmission. The overdrive automatically kicks off at 280 degrees F. The switch isn't too expensive so it wouldn't hurt to replace it if everything else checks out OK. The last thing to check on the electrical end that I remember, would be the plug connections to the above mentioned componets and the one that goes into the tranny above the shift linkage. That one is the one that goes to the solenoid. BE CAREFUL! the plastic connectors are old and brittle. TPS' are expensive. if yours is bad, you may want to try another approach. Some resourceful individuals have rigged up switches and manual potentiometers in place of the TPS. The solinoid has 12 volts to it the entire time the key is on. The ground wire is the one that is controlled by the PCM.

If all this doesn't fix the problem, you may need to have the fluid and filter changed to get your pump pressures back up.

 

Save yourself some $$ and use Dexron, the spec'd fluid. If you feel absolutely compelled to spend alot of money on tranny fluid, use DexVI.

 

Also make sure you are checking your fluid level in nuetral with engine running, not in park. Some trannys are running on low fluid due to checking in park.

 

Agreed, check the fluid level properly.

 

alright thanks for the advice guys I will try all of these things and see if things do not improve. how should i go about cleaning the TPS? do you think the linkage cable could be to blame at all?? how do I adjust the TPS? thanks again guys for all your help

 

Here's a good article on chrysler atf:

http://www.allpar.com/mopar/transmissions/fluids.html

From which...

"In testing done during development of ATF+4, Chrysler noted the following viscosity loss from shearing for the following ATFs (20 hour KRL Shear Test):

Dexron III - 40% loss
Mercon V - 19% loss
Type 7176D - 32% loss
Type 7176E - 14% loss
Type 9602 - 10% loss

You can see what a significant impact the new viscosity improver had on ATF+3 when you compare the 7176D and 7176E numbers. From the standpoint of viscosity loss alone you can see why Dexron III should not be used in transmissions that require ATF+3 or ATF+4. In terms of other basic performance parameters, ATF+3 (7176E) comes the closest to ATF+4, with Ford’s Mercon V a close second. [Which doesn’t mean that Mercon is acceptable.]

The goal in developing ATF+4 was to create a fluid that would match the performance characteristics of the current fluid (Type 7176D), but would retain those characteristics for at least 100,000 miles. The paper specifically notes that the anti-shudder properties of ATF+3 are usually degraded enough by 30,000 miles to cause noticeable shudder."

I know lubegard makes a black bottle which is a friction modifier for dexron fluids... It basically turns dexron into the + variety...

 

I guess you missed the part about seal compatibility.

 

http://www.lubegard.com/automotive/trans_atf_hfm.html

 

You mean this part?

"If there is a doubt about which grade of ATF to use, follow the owners manual recommendation. AFT+4 in certain specific tests was shown to be incompatible with certain seal material. This incompatibility may cause a premature failure depending on the duty cycle of the vehicle. The fluid will work as intended however, it may cause a seal failure."

Funny, because the Chrysler TSB calls for AFT+4 in ALL 518/618 transmissions to replace the 7176 or dexron II which is no longer available... and Which was speced for our trucks, not good ole dexron!

Thanks again for researching posted info before calling it hogwash.

 

Hey, no prob - you're welcome! Clipped from the same article you evidently didn't finish reading:

"Do not use Dexron with an additive. Richard Widman passed us an extensive report from reputable gas company Chevron, which compared ATF+3 fluid with Dexron plus various additives. They found that neither of two major brands matched ATF+3's performance specs.

I'm sure the additive manufacturer makes 100% truthful claims in this regard, just like all vendors trying to sell you stuff.

 

Looks like you missed this one too.:

http://dodgeram.info/tsb/2004/21-004-04.htm

Better hurry and catch up on your reading and Chrysler authorized technical specifications.