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th400 with gear vendors overdrive

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Old 08-28-2019, 01:52 PM
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Car: 91 Firebird Formula
Engine: 383
Transmission: built 700r4
Axle/Gears: 4.11, 9inch
th400 with gear vendors overdrive

ive searched and haven't found much either through the sight or on google.

anyway wondering if anybody here has used a th400 with a gear vendors and if you have do you have any install pics.
Old 09-09-2019, 03:15 PM
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Car: 1991 camaro Z28
Engine: Forged 370" LS turbo s480
Transmission: Built 4L80e Circle D converter
Axle/Gears: 35 spline 3.25 gears
Re: th400 with gear vendors overdrive

Originally Posted by ziggy89
ive searched and haven't found much either through the sight or on google.

anyway wondering if anybody here has used a th400 with a gear vendors and if you have do you have any install pics.
Have you thought of just building a 4l80?? Those gear vendors units are pretty pricey. They bolt up to the back of the transmission. For the cost of the unit you could buy a Jake's lvl 3 rebuild kit and save a bunch of money
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Old 02-28-2020, 05:59 PM
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Car: 1989 Firebird GTA
Engine: Motown Aluminum 427
Transmission: TH400/GVO
Axle/Gears: Dana 44 IRS 3.75:1
Re: th400 with gear vendors overdrive

I got one, good stuff. Check out the thread 'a firebird GTA the way they should have built it





this fit with no changes to the tunnel, and an unchanged TH400 crossmember
Old 02-28-2020, 07:16 PM
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Re: th400 with gear vendors overdrive

I have one behind my 700r4 in my 2nd gen.

Im telling you, there is NOTHING like having an effectively 8 speed transmission behind a ~400 hp V8. Not so much for drag racing it per se, but having these extra gears to downshift into at any speed. So worth the money...

Then with the double overdrive and 3.42's the gas mileage is phenomenal. Even at 90 mph I'm only doing like 2200 rpm... lol.

That said, it takes some practice to time the upshifts. Also if you get a shift **** with a button to activate the GV (which is what I did) itll be A LOT better and more fun than the foot switch.

Lastly be aware it's a firm shift. The tighter the converter the more firm it is. But like I said earlier, if you time the activation just right, you can often mitigate most of that. It's not to the point of being objectionable (I have a 2500 rpm stall) but it feels like a good shift kit.

Last edited by ULTM8Z; 02-28-2020 at 07:24 PM.
Old 02-28-2020, 07:32 PM
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Car: 89 GTA ASC Conv., Prev: 89 GTA 6.3L
Engine: 5.7L L98 TPI
Transmission: 700r4 Automatic
Axle/Gears: 3.27:1 w/ JG1 Options:B2L, N10, U1A
Re: th400 with gear vendors overdrive

There was a GV OD after a TH400 in the 1988 and 1989 Callaway Corvettes which were built under RPO B2K in the model years 1987-1991. Automatics were available only those two years, and had an external kickdown switch on the throttle body. It was a very slick install.
Old 02-28-2020, 09:56 PM
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Car: 89 IrocZ
Engine: L98-ish
Transmission: 700R4
Re: th400 with gear vendors overdrive

Used a few in trucks and MH's I've had, behind TH400's and C6's, super stout, not sure you can break them. My first was manually selected, later ones with a fancy control panel.

All worked well.
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