Shift kit for th-400 whats it do? - Pontiac GTO Forum
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post #1 of 8 (permalink) Old 11-17-2011, 08:46 PM Thread Starter
 
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Shift kit for th-400 whats it do?

hi, i keep seeing shift kit mentioned here and there, i have a th-400 in my 67 gto ho, whats the shift kit do ?, and where do i buy it from thats assuming its something i need... thanks
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post #2 of 8 (permalink) Old 11-18-2011, 08:26 AM
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One of the previous owners of my car installed a shift kit. I was told it was for racing I guess because when shifting its distinct when shifting from gear to gear. I dunno.

I had it removed from my valve body. I didn't like the slamming into Reverse or in 1st. It banged and was harsh when upshifting. When the car would shift to second it was a harsh slam often with a clunk. I had to lay on the brake pedal when shifting into reverse or into 1st gear. If the car was idling high say 1K rmp the slamming was disturbing. Bored out holes in the seperater plate and a few not installed correctly parts also helped in this issue. I do know once the shift kit was removed it made a world of difference the harshness associated with the shift kit was gone.

I don't know what that advantage is to have a shift kit in a transmission for normal cursing. Personally from my experience, if you are just driving your car normally, cruising and enjoying the road I'd avoid the shift kit it will be a nuisance. I've talked to others with shift kits that just cruise and they don't like it. If you are gonna drive aggressively and utilize the HO and track it then a shift kit may be something for you. The aggressive shifting with the shift kit will give you added beefiness.

I looked at the shift kit that was in my transmission and compared it to a stock kit and lit looked nearly identical but the spring appeared beefier in the kit. I'm no authority on this just relating my experience with the kit.

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post #3 of 8 (permalink) Old 11-18-2011, 09:02 AM
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Shift kits boost line pressure and change the fluid flow path to the clutch packs in various degrees. They can also modify "when" the shift occurs. For a car that it driven on the street and raced every now and then, they are not needed for the TH400. The only time they are of value is in all out drag race competition. They cause hard shifts, wear and tear on the driveline, and can cause damage to internal tranny parts. My advice: If it's working fine, leave your TH400 alone.
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post #4 of 8 (permalink) Old 11-18-2011, 09:15 AM
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(Sigh... I posted a nice response, then my connection burped just as I tried to save it and it went off into the ozone... I hate computers. I'll try again...)

Shift kits: Generally work by making the transition time between gears shorter. Smooth upshifts are the result of one gear being slooowwwwly released while the next gear is being sloooowwwly engaged. The transition time is controlled by valves/orifices in the transmission that control hydaulic pressure on the various bands and clutches. During the transition, both gears are partially engaged and everything is slipping. Shift kits speed up the transition and make this process more rapid and abupt, hence the harshness. Good for racing (and trans clutch lifespan), not so good for comfort.

I've got a TransGo kit in mine that has three different calibrations, all increasing in firmness. I'm running the "middle" calibration right now. With the converter and gearing I'm running, at part throttle it's actually difficult to detect when the upshifts happen. I haven't had any experience with full throttle operation yet, owing to a tendency to toss the alternator belt when I hammer it (that I'm working on solving), but I suspect the experience is going to be "exhilerating". I can tell that when engaging forward or reverse from neutral/park it does hit a little 'harder' than it did, but it's not too bad.

Some kits (including mine) also provide the ability to hold any manually selected gear "forever" regardless of rpm, and likewise the ability to downshift into any gear at any rpm/speed. Again, useful for racing but obviously you're got to keep your head screwed on with this one. Selecting low at 70 mph would be "not good".

Like so many things with these cars, it's a compromise... do you want smooth shifts and docile street manners, or do you want max performance / lowest possible e.t.'s.

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post #5 of 8 (permalink) Old 11-18-2011, 12:29 PM
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Fiesta, bear in mind that Bear (pun intended) is running a 461 inch stroker motor pushing 500HP. The benefit of a shift kit in his case is warranted. His car is a completely different animal than your '67 or mine. For your stock ride, you don't really want or need it. My opinion, others will probably differ!!
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post #6 of 8 (permalink) Old 11-18-2011, 01:42 PM
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Quote:
Originally Posted by geeteeohguy View Post
Shift kits boost line pressure and change the fluid flow path to the clutch packs in various degrees. They can also modify "when" the shift occurs. For a car that it driven on the street and raced every now and then, they are not needed for the TH400. The only time they are of value is in all out drag race competition. They cause hard shifts, wear and tear on the driveline, and can cause damage to internal tranny parts. My advice: If it's working fine, leave your TH400 alone.
NICE explanation geetee.

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post #7 of 8 (permalink) Old 11-18-2011, 10:59 PM Thread Starter
 
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Quote:
Originally Posted by geeteeohguy View Post
Fiesta, bear in mind that Bear (pun intended) is running a 461 inch stroker motor pushing 500HP. The benefit of a shift kit in his case is warranted. His car is a completely different animal than your '67 or mine. For your stock ride, you don't really want or need it. My opinion, others will probably differ!!
well that expains it i'm not going to look at this anymore, i'm just cruising dont need any harsh feeling gear changes so thanks for the info everyone
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post #8 of 8 (permalink) Old 11-20-2011, 12:57 AM
 
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shift kits improve pressure and can be used on street cars if the right kit is used.
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