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#1 |
Registered User
Join Date: Dec 2009
Location: bakersfild ca
Posts: 115
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passing gear
im having problems with my transmission, its a th400. when it goes to shift from 2nd to 3rd its slips. but it only slips when the rpms are low. when i puut my foot down it shifts fine. i changed the modulator valve and it helped a little bit. also when i manually shift from 2nd to 3rd its shifts fine. what i was wondering is if there is suppost to be a passing gear on the 400s? if this is even the problem then thats great but if someone might know what exactly it is then i would be happy to know.
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#2 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: passing gear
The Th-400 has an electric operated passing gear where the detent switch downshifts the transmission to second gear. This would most likely not have anything to do with your upshift from 2 to 3.
Outside of a low fluid level this problem is probably internal as it could involve the pressure regulator valve or the control valve assembly. I am assuming that you adjusted the modulator valve when you installed it and that there are no vacuum leaks. Jim
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1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#3 | ||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,940
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Re: passing gear
"Passing gear" is when the transmission downshifts from 3rd to 2nd when you mash the throttle. If your detent cable isn't hooked to the carb... it won't downshift. I don't know about it being "electric"...
Gary
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'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
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#4 | |
Registered User
Join Date: Dec 2009
Location: DFW, TX
Posts: 764
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Re: passing gear
Quote:
Like Jim already said. Doubtful that is your problem.
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72 Cheyenne Super 1/2 LWB White/Dark Yellow 07 Avalanche 2LT 74 Sleek Craft Rebel Jet Boat W/Pontiac 400 Last edited by OhOneWS6; 03-28-2010 at 10:11 AM. |
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#5 | ||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,940
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Re: passing gear
I learned something new today... which is what is cool about these boards. I had no idea even the old TH400's from back in the day were electronically shifted. Cool...
Still passing gear is a downshift from 3rd to 2nd... not the other way around. ![]() Gary
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'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
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#6 | |
Registered User
Join Date: Dec 2009
Location: DFW, TX
Posts: 764
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Re: passing gear
Quote:
This is not the thread I was thinking but same info here. http://67-72chevytrucks.com/vboard/s...d.php?t=350456 |
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#7 | ||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,940
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Re: passing gear
Awesome! Thanks for the linky!!!
![]() Gary
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'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
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#8 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: passing gear
the TH400 electrick kickdown is for going into first gear. Even if you unplug it, you'll still get the 3 to 2 kickdown.
Either way, fluid level, or clutch wear is about the only thing that'll cause slippage. |
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#9 |
Registered User
Join Date: Dec 2009
Location: bakersfild ca
Posts: 115
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Re: passing gear
OK well how would i go about buying a passing gear or whatever its called. im a noob and don't quite know all the terminology. about ok how much will the parts set me back?
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#10 |
Between Trucks...
Join Date: Mar 2002
Location: Los Angeles, CA.
Posts: 3,830
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Re: passing gear
Not sure on the price of a stock kickdown setup. Might check out the Parts Board. Somebody on here said you can run a carb mounted nitrous microswitch for the kickdown, which would probably be cheapest. I'm running the Lokar setup which runs about $100.
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Beat it to fit, Paint it to match... ![]() Last edited by Sinister; 04-02-2010 at 11:06 PM. |
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#11 |
Registered User
Join Date: Sep 2009
Location: Syracuse NY
Posts: 110
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Re: passing gear
B&M setup, attaches to carb linkage
http://www.jegs.com/i/B%26M/130/20297/10002/-1?CT= Installation article for B&M kit (not a truck , but you get the idea ) good pics http://www.highperformancepontiac.co...all/index.html original style switch ,mounts near gas pedal http://www.americanclassic.com/Googl...70NOS-1970.htm
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1967 Suburban 292 3spd 1964 Chevy II wagon 1971 Monte Carlo 402BB 1964 Cadillac series 62 2dr 1964 Bonneville 2dr/ht 1967 GTO 1978 Chevy Van 30 1989 R30 Crew Dually Bonus Cab |
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#12 |
Registered User
Join Date: Dec 2009
Location: bakersfild ca
Posts: 115
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Re: passing gear
ok well heres yet another problem, when i put it to the floor it takes a while to shift, in any gear. but if i have it to the floor its shifts fine from second to third. but at a low rpm like say cruising it slips about three or four times if not more before it decides to shift. like i said before though, when i manualy shift from second to third it shifts fine no slipping or anything.
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#13 |
Registered User
Join Date: Feb 2010
Location: duluth mn
Posts: 108
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Re: passing gear
have you checked your fluid? in park, engine running, pull dipstick, wipe clean and check level. what color is it? should be red to pink. if its brown your trans is toast. also check engine oil. radiators can break internally and mix trans fluid and antifreeze. passing gear/downshift has nothing to do with trans slipping. you can also drop trans pan. as clutches wear material collects in bottom of pan. if there is a large amount in pan also a bad sign.
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#14 |
Senior Member
![]() Join Date: Mar 2003
Location: Colfax-California
Posts: 8,549
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Re: passing gear
On the pass side of the trans near the tailshaft there is a 4 bolt cover. That is where the governor is. Remove the cover and pull the gov out with a slight twisting motion. Inspect the nylon gear on the end for wear
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