Late 1-2 shift on fresh TH350
09-08-2003, 04:48 PM
#1
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Car: 1986 Iroc
Engine: 454 Demon 850DP
Transmission: TH350, 3500 stall
Axle/Gears: 3.73
Late 1-2 shift on fresh TH350
I just got the built up TH350 in my car and if I start out in first and bang it into second there is a 1.5 to 2 second delay. The 2-3 shift is great, quick and firm. It has a shift kit and I am running a 3500 stall convertor. Downshifting is immediate and firm from 3-2 and 2-1. Any suggestions?
09-08-2003, 07:28 PM
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Car: No more birdy
Check the vacuum modulator, see if its there, hooked up or diaphram is working. Some shift kits do that though some even eliminte the modulator function all toghther. 
09-08-2003, 07:47 PM
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Car: 1986 Iroc
Engine: 454 Demon 850DP
Transmission: TH350, 3500 stall
Axle/Gears: 3.73
I checked and the hose was connected to the modulator. The shop that did the trans suggested turning the screw in the modulator 1 to 2 turns in. I did that and no improvement.
09-09-2003, 01:08 PM
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Car: 1986 Iroc
Engine: 454 Demon 850DP
Transmission: TH350, 3500 stall
Axle/Gears: 3.73
I believe it is the Transgo shift kit. I use this car mainly on the track and I have a B&M Megashifter. I start in first gear and bang it into second at 6300 rpm but it does not shift immediately. It takes about 1 to 2 seconds to shift and then it is a good firm shift. I have tried it at 3000 rpm and it does the same thing. The 2-3 shift is perfect. Immediate and firm. The downshifts are all immediate and firm as well.
09-09-2003, 03:36 PM
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This is not an easy one to solve. You will have to the transmission out and reduce the the 2nd gear clutch clearance by about .040, now this will give you almost immediate manual shift. When I use to build these units, this was one of the things that had to be addressed. We did this by removing the clutch material off of a low/reverse clutch and sawing open the steel and putting it under the 2nd gear apply piston. Now there are oversize steels that will do pretty much the same thing.
09-09-2003, 04:05 PM
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Car: 1986 Iroc
Engine: 454 Demon 850DP
Transmission: TH350, 3500 stall
Axle/Gears: 3.73
Thanks for your help Probuilt. I have been talking to the shop that built the tranny for me. He wants the car back in to check it out. I was hoping I wouldn't have to trailer it back to the city again but what can you do. I will be mentioning your suggestion to the builder and thanks again.
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