TH400 vs. TH350 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

lukecp · 01-13-2003, 07:28 PM

I know a guy that has a stock TH400 behind a 305 in a '76 Chevy. If you hold the truck in first gear and floor it, the tranny will shift into second around 5500 rpm, even though the shifter is still in the first gear position. The shift is quite harsh. My question is, will a stock TH350 also make a harsh shift into second gear like that at a very high RPM?

dmurphy68 · 01-13-2003, 07:33 PM

you need to make sure that the vaccume line to the tranny is hooked up if it isnot that will cause it to shipft hard. there is a valve at the back drivers side that can go bad to. just my .02

crazy longhorn · 01-13-2003, 07:41 PM

Im not sure about the 350T, never tried that......but yes, the 400s will shift 2nd while locked in low.......& d@mn hard!

ozarkhippie · 01-13-2003, 07:59 PM

All stock 400's will upshift to 2nd when in manual 1st. 350's will hold 1st gear.

Longhorn Man · 01-14-2003, 12:11 AM

Not true, Th350s and TH400s along with the 700 and 200 overdrives will all upshift at a certian point regardless of where the shifter is placed.
There is a round deal on the side of the 350 and 400 trannys with a hold down deal like your mastercylinder. Inside that is a govonor. It is much liek the mechanical advance in your dist. Some are set higher than others, and if your tranny was behind a deisel originally, it'll shift at about 4000.
I think the overdrives have it in the electronics, but i am uncertian. Tell you what though, it'll scare the crap out of you when you think the shifter is in 2 when it is really in 1. Once the RPMs get below 6000 (this is on the wife's S-10 Blazer) the back tires will give a big howl as htey slow to about 5MPH and the truck is still doing 20MPH.

01-13-2003, 07:28 PM	#1
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	TH400 vs. TH350 I know a guy that has a stock TH400 behind a 305 in a '76 Chevy. If you hold the truck in first gear and floor it, the tranny will shift into second around 5500 rpm, even though the shifter is still in the first gear position. The shift is quite harsh. My question is, will a stock TH350 also make a harsh shift into second gear like that at a very high RPM? __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

01-13-2003, 07:41 PM	#3
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	Im not sure about the 350T, never tried that......but yes, the 400s will shift 2nd while locked in low.......& d@mn hard! __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

01-13-2003, 07:59 PM	#4
ozarkhippie Registered User Join Date: Nov 2002 Location: Eureka Springs AR Posts: 494	All stock 400's will upshift to 2nd when in manual 1st. 350's will hold 1st gear. __________________ Buy Sale or Trade 71 3/4 4x4 72 1/2 ton cheyenne 4x4

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01-13-2003, 07:33 PM	#2
dmurphy68 Registered User Join Date: Nov 2002 Location: Middletown ohio Posts: 1,058	you need to make sure that the vaccume line to the tranny is hooked up if it isnot that will cause it to shipft hard. there is a valve at the back drivers side that can go bad to. just my .02

01-14-2003, 12:11 AM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Not true, Th350s and TH400s along with the 700 and 200 overdrives will all upshift at a certian point regardless of where the shifter is placed. There is a round deal on the side of the 350 and 400 trannys with a hold down deal like your mastercylinder. Inside that is a govonor. It is much liek the mechanical advance in your dist. Some are set higher than others, and if your tranny was behind a deisel originally, it'll shift at about 4000. I think the overdrives have it in the electronics, but i am uncertian. Tell you what though, it'll scare the crap out of you when you think the shifter is in 2 when it is really in 1. Once the RPMs get below 6000 (this is on the wife's S-10 Blazer) the back tires will give a big howl as htey slow to about 5MPH and the truck is still doing 20MPH.



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