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GM Drivetrain & Suspension Chassis | Transmission| Driveshaft | Gears/Rear End/Differential | Traction Aids

??? Is this normal..free rev then hard grab 1st gear

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Old 04-14-2008, 06:56 PM
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Fluid is good connections are tight.
Took it for a test spin and it seemed fine...didn't try to do any 3-1 downshifts cause i don't want to break anything....
all i can check now is the tune.
Old 04-14-2008, 07:37 PM
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hey joe. pauls tbss did this when he first got it and it has a cut seal or something. i would contact the builder and see what they have to say.
Old 04-14-2008, 07:41 PM
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Originally Posted by Truckshop
hey joe. pauls tbss did this when he first got it and it has a cut seal or something. i would contact the builder and see what they have to say.
I did. They said they have never had a problem of this nature before so they were not sure what it was.
Do you know what seal was bad on the tranny?
Old 04-14-2008, 07:46 PM
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no i don't. pm him(red53gmc) he just went back to work but i can't remember if he is on days or nights?
Old 04-14-2008, 08:05 PM
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Originally Posted by Truckshop
no i don't. pm him(red53gmc) he just went back to work but i can't remember if he is on days or nights?
10-4. By the way got all the junk in the cab painted up...at least everything i have the patience to paint anyway lol.
Old 04-15-2008, 12:56 AM
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Checked he tune and the WOT upshift is at 47mph on the 1-2 the downshift 2-1 was at 40mph so it had 7mph to play around plus the highest i tried this was at 35mph and it does it at anything over 25mph......
ideas?
Old 04-15-2008, 02:01 AM
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It sounds like you're losing fluid from the forward clutch. The easiest explanation for fluid starvation from a throttle hit preceeding rapid engine RPM increase would be that it's blowing out past the forward clutch lip seal from the centrifugal force. Line pressure seems to be coming up enough eventually to overcome it, but you feel the gap as forward clutch disengagement and end up with what feels like a neutral drop... something like that, right?
Do a test drive under the same conditions, but with the vaccuum line to the modulator disconnected. If the symptom goes away it's probably a leakage problem, I would think. (BTW, part throttle shifts will be very violent at max line pressure. Do not drive it long like that.)
Old 04-15-2008, 09:00 AM
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Originally Posted by James B.
It sounds like you're losing fluid from the forward clutch. The easiest explanation for fluid starvation from a throttle hit preceeding rapid engine RPM increase would be that it's blowing out past the forward clutch lip seal from the centrifugal force. Line pressure seems to be coming up enough eventually to overcome it, but you feel the gap as forward clutch disengagement and end up with what feels like a neutral drop... something like that, right?
Do a test drive under the same conditions, but with the vaccuum line to the modulator disconnected. If the symptom goes away it's probably a leakage problem, I would think. (BTW, part throttle shifts will be very violent at max line pressure. Do not drive it long like that.)
I'll try it out. And yes it feels very much like a nuetral drop then it suddenly grabs.
almost as if it were a standard and i pushed in the clucth reved it and popped it.
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