Engine/Transmission (1994 - 1998) Torque Converter Questions from a novice

[VicR]

1) What does it mean when the RPM's jump up 300 or so, 2 or 3 times, when the torque converter is locking up? Not every shift - just occasionally. Happens in OD at 55 MPH and 3rd w/ OD off at about 36 MPH. Doesn't happen in 3rd with the OD on. Not a shudder or a shake, just a surge. When it happens I just back off on the throttle and it seems to lockup.



2) Using the mystery switch I put the TC in 'unlock' mode and could not make it surge. Thats why I am pretty sure its the TC locking up. What is the downside of driving in unlock mode? I assume MPG would suffer because it wouldn't be as efficient, but anything else?



3) Since I have owned the truck, whenever the TC locks up at 55 MPH, the pressure needed to push the throttle drops by at least 50%. I can't figure out what occurs to make this happen. I don't see how the TC is attached to the throttle at all...



By the way, the truck is a 97 with a Pacbrake and a torqlock controller. Wife currently has the pacbrake off because she doesn't like it on for around town driving.



Thanks.

- Vic

 

[Snow man]

Vic,your TPS sensor is acting up,either clean it or replace it and your troubles should go away. Driving it in unlocked position is OK if your empty AND have a trans temp guage. It can and will overheat if left un unlock to long,especially the stock tc its so loose it generates a lot of heat.

 

[98rammer]

yep, sounds like the tps problems. i have an unlock switch and it saves my transmission at my power level. i have a problem with the stock converter locking up as early at 45mph in OD at 1200rpms that's just not right!

 

[VicR]

Thanks

Thanks - I had thought the TPS was innocent on this one because it only happens on initial lock-up, but after rereading some old TPS posts I see how it could be the guilty part.



One more question - what constitutes a good TPS cleaning? Can it be cleaned on the truck or should it be removed for best results? I'll get a can of the cleaner at radio shack, but am not sure what to spray.



Thanks again,



-Vic

 

[Joe G.]

Just soak it down where the shaft comes out. Then work the throttle linkage back and forth. If a few doses of that doesn't work you can try pulling the three wires loose from the cable and see it that fixes it. It's good preventive maintenance to give it a shot of cleaner when you change oil.

 

[VicR]

Thanks. I think that did the trick. Everything seems normal now. However the throttle pedal pressure while in lock up is still super light. This is the first automatic diesel I've driven so I don't know what to except. I'm going to see if I can find a used one on a lot this weekend and see how it compares.



Thanks again.



-Vic

 

[Joe G.]

Vic,



The throttle pedal should feel about the same regardless of the gear. It may feel harder at low speeds than higher because there is a break over point in the linkage. It should never be super light. Two things to check. Make sure the ends on the throttle return spring are ok. It's a double wound spring so there should be two curved together on each end. Sometimes one of them will rust off so the spring is only working on one coil. The other thing to check is to see if the cable is on the kick down lever on the transmission. Also check the kick down lever spring. It may be missing. It goes from the lever to an eye on a transmission bolt.

 

[Snow man]

Vic,did you buy it used? If so I suspect a previous owner had a BD torque lock installed. They have that same deel ,they pedal gets light under your foot as it pulls the Tv cable once in lockup. You will see if it has one,it sits on drivers side of trans,above pan,hooked to TV cable.

 

[VicR]

Snowman,



Yes, it does have a BD torqlock. I take it the light throttle is a trait of them?



I'll give BD a call and see if they have any way to tighten it up. Not that its a big deal, but it gets your attention when the resistance goes away on the pedal the first few times.



=Vic

 

[Snow man]

Vic,that is just the way the BD torque lock works,so its working like its supposed to.

 

[VicR]

Thanks to all for the help and advice. AFter cleaning it I had only a very sporadic problem with it, so I just went ahead and swapped it for a new one and the problem seems to have gone away. l



Thanks.



-Vic