Could it be the transmission

[BPaulsen]

'92 D250 with 180K, bone stock. Never any trouble 'til a few months back. Power down, extremely sluggish the first few miles when cold. Like a roadblock. bicycles were passing me away from the traffic light.



Went to the "experts" at Cummins South Pacific for pro diagnostics, super expensive" shop, but I wanted the experts to tell me what's wrong with my truck. They checked everything for hours (at $91 per hour), diagnosed weak VE fuel injection pump and lift pump. Replaced both, injection pump twice (somethin' broke inside the one I got after 86 miles!). The whole thing has cost me north of $3,5K now. Performance still not up to where it was before I noticed lack of power.



First I though . . . maybe my original pump was turned up, that's why it feels like I don't have enough power, so I'm ready to turn up the pump, as per instructions on this Web site.



Just when I'm about to do it, I have another really bad morning, cold, like California cold (about 55 degrees), and my truck feels soooo slow, doesn't want to get up to speed, feels like its holding the first gear, doesn't get enough juice to get up to speed to shift to second.



That got me thinking. What if I have a torque converter or transmission problem? If I rev the engine in neutral, it revs up happily. Just when I DRIVE the truck, especially COLD for the first mile or two, it's almost unbearable. Once it's warmed up, it's ALMOST as good as it used to be. Almost.



Question: how should I proceed? Can it be the torque converter or transmission? If so, which one? Why is it so noticable when cold? Shouldn't cold (thick) trans fluid be more powerful than hot (thinnner) one?



Lotsa questions, I know, but after spending a fortune, I don't want to buy a new converter, or 727 OD trans, or both, only to find out it wasn't the problem.

If I go to a trans shop, they'll sell me somethin', that's for sure.



What to do, and in what order?

 

["Mad Max"]

When in gear, does the engine rev up (stall out the converter), or does the engine feel like it is being held back mechanically somehow? Can you brake-torque the engine (put in gear, hold the brakes, rev the engine at same time) to see if the transmission is stalling correctly? If the engine won't come up then I'd say it's a fuel issue. If the engine comes up and the transmission is trying to spin the tires - well, that is what would happen if it all was working good. If you have power and the engine is still held back and the transmission won't stall out then I'd maybe lean towards a transmission/converter issue. If it doesn't stall out I'd say maybe the converter is going bad. TCI CTD converter for a 93 Cummins - from Summit Racing. Inexpensive, good results, 6-hrs of your own labor. You'll need a service manual.

If the engine has no power, gotta be fuel.

Cold transmission fluid won't flow through the transmission like it needs to so hot fluid is where best results are. If fluid is burnt then it's eating itself. I'd replace the converter either way, actually.



- M2

 

[dpuckett]

Tip#2- dont go to a Cummins shop. The DOdge diesels are the black sheep of that family for some reason. Any time I have gone into one, it has been give part number (91 had no data tag), get and pay for it, and walk out. Try to find a shop that specializes in pickup performance. Also, prepare to do some of your own work.



Tip#3- get gauges. This will give you a baseline. If you can only get to 12psi boost and 900 pre turbo EGT, you have fuel issues. If you can get to 1100deg, and mid teens boost, but only go 70mph in OD with 3. 54s (60 with 4. 10), then you have transmission issues.



Daniel

 

[BPaulsen]

1 Response

Thank you guys very much for the advice. There's no obvious holding back or slipping or fuel starving . . . that makes it so difficult for me.



Checked trans fluid: it's up to max and super clean.

I then warmed up the truck by driving it to work. Tried to observe what exactly might be wrong but couldn't as it behaved pretty normal.

When at work, I put it in "L" gear. Held it in position by holding the brake pedal with the left foot and trying to do a "burnout" of some kind by reving it up. Engine comes up to speed kind of normal (no screaming, no holding back); I'm able to keep the revs up, probably near redline (don't have a tach), but I can't spin even a single wheel. Coudn't stall it either. Shouldn't I be able to spin a wheel on a stock truck that's working as it should?



What do you make of that? Next step?



Thanks!

 

[Philip]

If your getting that much RPM with the brakes locked and not spinning tires. Eather you have the best set of rear brakes anyone has ever seen or you have a converter that is bad,or a clutch pack slipping.

 

[cerberusiam]

Thats pretty normal for a stock setup and rear brakes that are working. Had the same results until I put a different turbo on and cranked the fuel up.



How much smoke was it blowing?

 

[BPaulsen]

No smoke. The only time I see any smoke is a small puff when it's cold and I start it up in the morning and when I try to kick the ***** out of it by flooring it on the freeway on ramp, pedal all the way to the metal 'til it hits redline and shifts up. Otherwise this is a non-smoking truck. Maybe it's not getting enough fuel after all since the pump is set on economy . . .

 

[cerberusiam]

Definitely sounds like its in econo mode. :-laf



Thats not neccessarily bad with the price of fuel, just not much fun.