Question Noob to PSD - Cruise Control Problems

Hi, All
I'm new to PSDs and to the board, too. Did a search on cruise controls and didn't find what I need.

I just got my 96 on the road - 7.3 turbo PSD, Auto, long bed, 31.5's, dual 5 inch stacks, EDGE programmer. and it has about 200K on it. Starts easily and is extrEEEmely strong. Well, compared to my old DUDge 360 gasser.

First, it only gets about 14 at 60 cruise, flat road on the Ohio interstate. I'm disappointed with that, since many others have said they get or exceed 20 MPG. I'd like to figure out what to do to get more out of it. BTW, at 60, it's cranking 2000 RPM. I'm not sure what rear end gears it has but 2 grand aint all that hateful so I would imaging it has something longer than 4.11s.

Anyway, with the cruise set, the engine surges between 2000 and 2200 RPM and it does this all the time. The speedo sets rock solid on 60. Now, I am familiar with cruise controls and automatics and I don't believe this thing is normal. My other vehicles don't surge at all, especially on flat level roadway.

Does anyone have any thoughts on my 2 problems ?

Roger
Central Ohio

My first guess would be the torque converter is locking and unlocking. Could be a problem there.

rondog said:

My first guess would be the torque converter is locking and unlocking. Could be a problem there.

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First, welcome to SDD. Yeah I'd have to agree. The TC shouldn't be locking, unlocking at highway speeds. Is the truck 4X4?? You probably have 3.73s or something along those lines it it. Mine turs 16-1800 at 60-65 with my 3.55s. That and if your TC is bad could play into thefuel milage. I get 16-18 on mine, and I don't really baby it. I typically run 70-75 on the highway.

Hi Fellas
Thanks for the welcome.
I forgot to say that it is 4WD and for the most part, the 4WD seems to work well. At times I have a bit of trouble shifting HI to LO on the transfer case but can manage most of the time.
I haven't been able to hear anything moving, locking/unlocking due to the noise level from the twin stacks. There is no muffler or cat so it sounds like a class 9 semi - loud. In fact, on a long trip, it gets old. I learned about that when I had a Corvette with side pipes. They let out at the back edge of the door, right under your ear.
The truck has about 200,000 miles on it and I don't know if there was ever any service done to the tranny. The gal I got it from had it for several years and did nothing to it. And neither of us can find the fella she bought it from. I guess I should do a title search to try and locate him.
If the tranny is having some problems, I have another truck that I bought as a "total" primarily bcuz the fella had the tranny rebuilt 2000 miles ago by a reputable shop. So it's my spare, tho I was going to make that truck into my snow plow truck for the house, as I have a lane that is 1/3 mile long and I need to plow in winters.
If the TC is locking/unlocking is there anything I can do or should look for to remedy other than pull it ? What are your thoughts on putting some LUCAS in ? What about the "lock line" and (possibly) forcing it to lock ? Would that tell me anything ?

Roger
Central Ohio

The PCM in 96 autos has terrible torque convertor control and allows it to unlock any time you release the throttle. Chips can be burned to a different PCM code to eliminate the problem but I dont know if you edge addresses it or not.. It's easy enough to install a switch to manually lock the convertor and a light so you know when its locked. Jim has some pics in his webshots that show which wire to use for the lock and/or light.

TC lock led pictures from trucks photos on webshots