hello all,

im new to the site and new to the Cummins - -i recently bought a 94 3500 4x4 with 124k on it - the tranny was supposedly rebuilt about 20k ago.

i love the truck but the trans makes nervous, it shifts fine through 1-2-3 then it does some weird stuff between 40 and 60 mph, goes into over drive then jumps back out sometimes, goes into overdrive then seems to go into a torque converter lock up{?} - -the rpms drop to around 1600-1800 rpm at 60 mph.................but it jumps out like every 30 seconds sending the rpms to 2000-2100 - - -back and forth - - -driveing me crazy..........

if i take it out of overdrive it runs 2500-2600 rpm at 55-60 mph which feels like its going to pop out of the hood and slap me in the face

whats the deal? is it just the nature of the beast? ive heard nightmare stories about early Dodge Cummins transmission combinations - - -

this is a plow truck and a trailer puller so i need to be confident in my rig.

any help or advice on were to start and what to do or look for is greatly appreciated

thank-you

 

when i wired my pyro guage i just grabbed a hot wire under the dash (not the smartest idea) drove my truck for about 35 miles on the freeway and it was doing the same things as you have described. so i pulled over and unhooked the guage and it was fine. never found out what wire i grabbed but would asume it was to do with the tranny. that is just my story as i don't know enough about trannys and the electrical supply to fully understand. have never had that problem since.

 

Sounds like the TPS or the brake light switch. Both can cause lock-up issues are are pretty common.

 

ok forgive my ignorance, im a reasonably adept mechanic and can do most anything...................but.................... ....

what's a tps?

i do have a touchy brake light switch, i noticed one day working under the dash that my brake controller was "on" so i finally found that just pulling up on the pedal a little bit turned it - - - think there might be a wireing short or something causeing and issue with the transmission???

what would i look for ?

while we're talking about my ignorance on cummins motors, , i was told this truck has a bigger turbo and a "cam" in the injector pump? - - the turbo says "swittzer" on it and the injector pump looks pretty original - -is there something i can check with out takeing the pump apart to verify this information?

ive put a K&N cold air intake on her, and it has 4 inch exhaust on it right now, my buddy is building me a 4x8 inch rectangle stack here in a week or so, i have a hal-pak box between the cab and flat bed and the pipe will run up the center between the bed and box with a big nasty flapper on top of course.........

thanks for the help !!! looking forward to more...


"help Boss make a monster"

 

TPS switch = Throttle Position sensor

TPS testing and adjustment

 

ill be checking this as soon as i have an opportunity - - -thankgiving coming up ya know- -momma won't like me under the hood while families in the house,

thank you for the tip

Al

 

I doubt they changed the cam in the pump. More than likely it has a different fuel plate in it maybe they called it a cam plate......you definetly have a different turbo as they can stock with Holset turbos.

 

ok thanks..............being an old powerstroke fan, i have 2 tuners sitting on the shelf now that are useless to me, and the 12v being a mechanical motor i have no idea what can be modded and still keep it dependable. I am not going to be pullin sleds or doing monster mudding with this rig but would love to get as much power and attitude out of her as posable without blowing stuff up................whats the most common things done to these beasts to tweak em up a bit?

thanks for all the help, this is a good site. ive been to a couple other forums and the people acted like i was bothering them because i wasn't driving a 60,000 dollar 4 door dually haulin cattle

Al

 

get gauges(boost,pyro,trans temp)<-- first thing!!! tourqe converter, valve body, pull the plate,slide the afc and crank it open, set timing to 18.5* out, head studs, and a boost elbow.should be a good start for ya

 

ok gauges are pretty self explanitory - - and i think i need a tourqe converter now, so whats a decent brand and how much can i wxpect to pay for one?

the fuelplate and timeing stuff sounds pretty intense...........are these hard things to do?

head studs im assuming are for added strength from over fueling?

and whats a boost elbow and what does it do


thanks for the help