40 mph vibration update

melmount

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Ok, I have been chasing this low 1300 to 1400 rpm vibration in 4th gear for a while now. I originally found a bad #8 injector.(changed that) Found unplugged(sort of) uvch on pass side, it did not ohm out corectly.(fixed it)
I replaced the tc, changed tranny fluid, tried a different idm.
I replaced the u joints all 3 of them. Even the carrier bearing. Turns out the advance auto u joints were junk. Had the drive shaft shop balance it. We missed the u joints. I brought it back, found them to be no good. Replaced all 3 then rebalanced the shaft. I bought a new tranny mount.
I now can say its pretty good.

Heres the issue:::::
When it sits overnite I get in it to goto work. About 2 miles into the ride the engine temp gauge goes to the first white line.(being at the lower sort of warmed up level) Here is where the truck starts a bad vibration or shuddering like it did originally before all these new parts and repairs, I manually, with a switch unlock the tc(i tapped into the wire and can unground it) The shaking stops and truck drives fine. Keep in mind the motor is still not warm or hot. I have no issues with cold starts. I do not hear a skip. The injectors buzz and cct fine. (Scruffy on here says its driveline) (I aggree)
I continue to drive maybe another 3miles til the temp is fully hot. I can now allow the tranny to lock and unlock on its own. It does not shake any longer.
I now park at work for like 6 hours and come out and the truck is fine. Its only the first start of the day, after the trans warms enough, so that the pcm will allow the tc to lock.(pcm controls it differently til a certain temp is reached) Once its hot its fine.
What in the trans can cause this?
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JLDickmon

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there might not be anything wrong with it..
it may be just not warm enough for complete combustion.
 

melmount

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well, if its an injector not completely firing due to temps, I would assume its weak.
I tried the tc lock up different today, I started driving it with out warming it. I let it shift to third then locked it myself. It vibrates the whole truck til its fully hot. I have a 99 and an 01. the 99 does not do it. The 01 if the tc locks before its at 200 degrees(approx) it vibrates. But I have made it a ton better then its been. Its cool to drive now.
 

JLDickmon

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well, not necessarily..
my truck has always had a "rumble" similar to what you describe.. and I've done all the same stuff..
now that I had the trans rebuilt last month, you can feel what you would call a dead hole on a gasser..
cyl #8 fails the contribution test..
however, if you romp on the go-pedal, it seems just fine..

see don't forget that the fuel curve is predicated on temperature first, load second...

so be honest with you, unless you have more symptoms, ie., squirter fails a buzz test, t/c clatters, fuel runs out of the exhaust like Sagebels' truck did... I'm not sure I'd worry about it.
 

JLDickmon

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oh yeah..
guess which injector fails the contribution test on my truck.....
 

melmount

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The way it is now, its tolerable. Theres about a 2 to 3 mile period where its funky while warming. I just unlock the tc with my switch.
Before i fixed all the stuff i just did, it was every time the tc was locked, real bad shaking(violent). I swapped idm's with my wifes. She says that its vibrating at idle now on hers. Maybe thats when most of my vibes went away. For a while it was almost not driveable.
I may get a beans 140 volt idm and give her hers back.
The vibration I am talking about for this brief warm up period is pretty serious. Not like a minor shake from a wheel out of balance. The steering wheel is bouncing up and down.
I dont mind flipping my switch for a mile or two though.
 

melmount

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oh yeah..
guess which injector fails the contribution test on my truck.....

I failed number 8 but replaced the injector. I pass the buzz and cct now. Passed it several times. No fuel in the oil either. Not really using and oil.
 

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