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Old 10-19-2005, 08:35 AM   #1
Kustom
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th400 shifts fast

I just finished changing the 700R4 to a th400 in my 85 blazer. When I went out for the test drive it shifted through all of the gears very fast (by 30mph). The truck then lugs up to speed. Any ideas on what could cause this?
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1969 Chevy LWB 350, vortec heads, pro perf intake & powerglide
1985 Chevy K5 Blazer
1951 Buick 2 door HT; 350/350 combo, sub frame, disc brakes
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Old 10-19-2005, 11:19 AM   #2
Russell
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Re: th400 shifts fast

Vaccum modulator probally needs to be backed off 1/4 to 1/2 a turn
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Old 10-19-2005, 11:20 AM   #3
JIMs70GMC
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Re: th400 shifts fast

Or replaced, but adjust it first.
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1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs
1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX
1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears
1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now.....
1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone.
1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed.

1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm
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Old 10-19-2005, 11:22 AM   #4
Kustom
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Re: th400 shifts fast

How do I go about adjusting this?
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1985 Chevy K5 Blazer
1951 Buick 2 door HT; 350/350 combo, sub frame, disc brakes
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Old 10-19-2005, 04:14 PM   #5
Russell
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Re: th400 shifts fast

Take the vac line off and look in the hole. If it is an adjustable one, you'll see a notch you can turn with a small flat headed screwdriver.

If it isn't adjustable, then you'll need to replace the whole thing.
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Old 10-23-2005, 10:52 AM   #6
bigblue1968
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Re: th400 shifts fast

what are you gonna do with your 700r4?
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Old 10-23-2005, 05:45 PM   #7
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Re: th400 shifts fast

Ive seen some that you adjust with a small allen wrench too...
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