11/8/06
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Hi Mike,
I have a huge problem (very frustrating)…
I bought a 1972 Pontiac Ventura II about three months ago, knowing that it had a problem with the tranny – that it will not shift out of first gear for about three miles when cold. The engine is a big block Pontiac 400 reportedly from a mid-1970’s Firebird or TransAm and the tranny is a THM350 with a B&M top-loader shift kit. Again, it will not shift out of first gear until the engine is up to operating temp (200 degrees or 3 miles of driving at a max 20mph right now). After the “warm-up”, the tranny shifts fine with no problems at all.
I have moved the vacuum line around, changed the tranny filter & oil, and replaced the vacuum line to the Modulator – all to no avail. Today, I am going to replace the Modulator (which appears new) and the Governor. Any idea what else could be at play? One mechanic suggested I make a vacuum canister to place between the manifold & Modulator, as I may not be getting sufficient vacuum with the racing Cam setup… is that a possibility?
Any help would be appreciated! I can call you to discuss, if you think that would help.
Thank you,
Dave Fontalbert
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Dave,
It sounds like your 350 has possibly a sticky shift valve. Usually if something is loose or worn out it will leak more after warm up or after the fluid thins out. But your problem is cold not hot. Usually cold problems are clearance problems, shift valve, governor etc. Also take a vacuum reading at the modulator if it has 6-10 in. of vacuum it should shift, but this is why everyone doesn’t build automatic transmissions. If you need more assistance please call.
Mike
Mike’s Transmission
Lancaster CA
(661) 723-0081
You can also email Mike Stewart at trannytech@dragracingonline.com
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Tranny Tech [8/8/06]
Mike Stewart Can Cure Your Automatic or Powerglide Problems |
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