Mostwanted

Why is it that when manually switching the truck into overdrive, the tranny seams to slip into another gear before going into actual overdrive? Is this the torq-conv slipping og is this normal? I sometimes turn off the overdrive in my truck when I am cruising under 45mph to maintain a little more revs. When I turn the overdrive back on the RPM's will drop to around 2000-2100 @45 mph for a few seconds, then drops all the way down to about 1500-1600 rpm in final overdrive. :

DF5152

its the torque converter locking an unlocking when u r in 3rd and hit the button it probably unlocks the converter shifts in to overdrive then locks the converter.

Srigs

I agree with DS5152. You go from locked up in 3 (yes the tranny locks in 3rd with OD button off) to unlocked in 3rd then shift to 4th and finally locked in 4th (OD). Normal.

dalton4

To prevent tranny damage the system is design to not shift while in tc lockup. That is why it goes through the above shifting routines.

berner

I was thinking of installing a mystery switch. How hard is it on a stock tranny to run it through the gears with the TC locked up?<br>Thanks<br>Ron

dersequim

Berner, Go to Dieseltrans.com and ask Bill K. That question. You will get the TRUE answer!!

berner

I checked DTT's Forum. Looks like Bill doesn't recommend any type of TC lockup system with a stock tranny.

Sootblower

If driving 45 to 55 mph in mountain terrain, the TC lockup in/out can drive you crazy. I put in a switch that only disables lock up but does not force it on. i.e. it only opens the circuit to the OD solenoid and never grounds it. This has cut the irritation factor WAY DOWN such that I can live with that ugly transmission now. I would not tow heavy though since there is more heat generated. Empty load is fine for me, fluid stays bright red.

98rammer

[quote author=Sootblower link=board=16;threadid=12785;start=0#121857 date=1048962249]<br>If driving 45 to 55 mph in mountain terrain, the TC lockup in/out can drive you crazy. I put in a switch that only disables lock up but does not force it on. i.e. it only opens the circuit to the OD solenoid and never grounds it. This has cut the irritation factor WAY DOWN such that I can live with that ugly transmission now. I would not tow heavy though since there is more heat generated. Empty load is fine for me, fluid stays bright red.<br>[/quote]<br><br><br>i have done the same...except it's more for the tranny being overpowered when in locked up. i haven't had any tps issues. it's great be able to control what that converter clutch does.<br><br>Tom

Tgrfan2

I did the same on my 95 and now want to modify my 98. Which wire did you use to disable the lockup 98rammer? ???

StakeMan

A lockup or mystery switch on a stock tranny can be bad. IT all depends on how you use it. Every aftermarket tranny builder has thier own recomendations on using lockup on thier modified trannies, but I think they all agree that lockup switches can kill a stock tranny.

Sootblower

Hi StakeMan,
I think the difference is that when you only force the &quot;unlock&quot;, your only enemy is heat when giving lots of throttle towing or climbing or both. Use 3rd locked in this situation. The situation that causes damage is when you force the &quot;lock&quot;, especially when tranny is switching gears. The clutch packs, TC clutch and bands would then take the shock load of RPM drop instead of fluid coupling in the TC. There is a big difference here. Correct me if I am wrong.

98rammer

[quote author=Tgrfan2 link=board=16;threadid=12785;start=0#124095 date=1049458173]<br>I did the same on my 95 and now want to modify my 98. Which wire did you use to disable the lockup 98rammer? ???<br>[/quote]<br><br>if i remember right, it's B11. i had to install the jumper wire in main fuse box and then i simply put a switch in that allowed for the pcm to not be able to ground. flip the switch, the circuit goes through, and the pcm can then lock up the converter at stock programming. i used the instructions from the TST booklet..just doing the UNlock situation.<br><br>Tom

redruM Hauler

lets aproach this from a differant angle, towing a small load (7000#) cruzing down the hwy @ 70 with OD off (2500-2600 rpm) then switch OD on RPM increase 200, then drop to 2100, then again to 1600-1700 how (without changing tires or gears can i maintain the 2100 rpm range (will the "mystery switch do it?)

3.55's & 285-75-16's, motor is stock

Eskimo

and lemme tell ya.. TC locked shifts can be HARD shifts!!! My ATS can be harsh at times, if the throttle isn't feathered... especially 2-3 or 3-2 shifts...