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  #1 (permalink)  
Old 12-26-2005, 12:01 AM
72NOVA454
 
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TH-350 vs Turbo 400

I am currently upgrading my 72 Nova to a 550 HP BB Chevy and will be completed next month. I have the TH-350 transmission with a posi differential, stock torque converter and approximately a 3.00 gear ratio (stock). I will upgrade those things next winter (winter of 2006/2007 due to budget reasons). A couple people have told me the TH-350 won't last and is not strong enough and that I have to upgrade to the Turbo 400. I will do this next winter - not this winter. Will my transmission last this upcoming summer when I am racing my new 468 Chevy around town or must I upgrade to the stronger Turbo 400 right now?

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Old 12-26-2005, 05:42 AM
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TH-350 vs Turvo 400

I'm by no means a trans expert but from past experience with 350's I would
go with the 400 . I have one in my coupe and although no where near the HP
you have, it came out of a 79 Grumman step van "disassembled / inspected " slid it in and have no worries when going anywhere .with an adjustable vac. modulator you can fine tune your shift points to your needs. They take a bit more HP to run but they are tough. I have never had a 400 fail me (350's &
4L60E's, thats another story). There are members in this forum that can better address your needs, it's the holiday weekend but I'm sure they will reply.

Good luck
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Old 12-26-2005, 06:07 AM
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hey 1939p7, i have a 350 trans ,can you adj it for longer shift
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Old 12-26-2005, 09:52 AM
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Quote:
Originally Posted by leejoy
I am currently upgrading my 72 Nova to a 550 HP BB Chevy and will be completed next month. I have the TH-350 transmission with a posi differential, stock torque converter and approximately a 3.00 gear ratio (stock). I will upgrade those things next winter (winter of 2006/2007 due to budget reasons). A couple people have told me the TH-350 won't last and is not strong enough and that I have to upgrade to the Turbo 400. I will do this next winter - not this winter. Will my transmission last this upcoming summer when I am racing my new 468 Chevy around town or must I upgrade to the stronger Turbo 400 right now?

How long your t-350 lasts with an honest 550 hp big block will depend on 2 things :

the current condition of the t-350 and how much traction you have. IF you have traction , the t-350 trannys life will be short even with a 3.00 gear

The stock converter will not function well I imagine . The camshaft to get 550 hp from the engine would require an upgraded converter.

good luck

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Old 12-26-2005, 10:26 AM
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Quote:
Originally Posted by steve t
hey 1939p7, i have a 350 trans ,can you adj it for longer shift
with an adjustable vac. modulator you can , goto your local auto parts dealer
and get one. just don't run the adjuster past the thread end . I'm sure they are also for the 350.
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Old 12-30-2005, 11:30 PM
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Quote:
Originally Posted by steve t
hey 1939p7, i have a 350 trans ,can you adj it for longer shift
Hay steve can you give me some input on how you adjust a 350 chevy trans for a longer shift. I have one theat I feel needs to shift from first to second a little later.
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Old 01-03-2006, 05:23 PM
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A th350 trans can be beefed up to handle a high output BBC. However, a stocker will not last very long. Hard to say without knowing the condition of the trans and your driving style. But a good condition th350 should last a summer of some abuse. Installing a shift kit could extend the life by reducing slippage.

400's can do very well in stock from with just a shift kit and a governor adjustment for higher rpm shifts. Plus there isn't that pain in the butt down shift cable on a 400, it is electrical.

So, I prefer 400's behind high powered engines because they hold up with just a stock rebuild and a shift kit.

A 550 hp BBC with have a hard time launching a 74 Nova with a stock converter and 3.08 gear. Don't except any wheel stands with that combo. A 3.55 gear and a 2600 stall should be the minimum with that setup.
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Old 01-03-2006, 09:55 PM
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If your just setting up the car and don't have a trans/driveshaft yet go for the 400.No worries and you only lose 6hp.
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Old 01-04-2006, 09:22 AM
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Quote:
Originally Posted by 454C10
A th350 trans can be beefed up to handle a high output BBC. However, a stocker will not last very long. Hard to say without knowing the condition of the trans and your driving style. But a good condition th350 should last a summer of some abuse. Installing a shift kit could extend the life by reducing slippage.

400's can do very well in stock from with just a shift kit and a governor adjustment for higher rpm shifts. Plus there isn't that pain in the butt down shift cable on a 400, it is electrical.

So, I prefer 400's behind high powered engines because they hold up with just a stock rebuild and a shift kit.

A 550 hp BBC with have a hard time launching a 74 Nova with a stock converter and 3.08 gear. Don't except any wheel stands with that combo. A 3.55 gear and a 2600 stall should be the minimum with that setup.
thanks buddy. I will use your advice. I will be doing the work next winter and am preparing for it now by gathering information. What exactly does the shift kit do? Also, I heard that I may have a good strong stock 10-bolt rear end gear in that car (72 nova). I read an chevy article that said if it has the 11/16" bolt heads on the ring gear that it is a keeper and will hold up 9 second drag racing. your thoughts?
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Old 01-04-2006, 10:17 AM
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if it has square corners at the bottom then it is a 8.5 10bolts, meaning a good rearend.
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Old 01-04-2006, 12:51 PM
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This may help with the 10 bolt rear ID.
http://chevyhiperformance.com/techarticles/49998/

A shift kit will make the transmission shift faster. This reduces clutch slippage and wear. A shift kit can be installed with the transmission in the car. How fast is the trans shifting now?
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Old 01-05-2006, 01:51 PM
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go with the 400

I'd definitely go with the 400, but you need to ask yourself this.. do you want to be able to sell the 350 for a few bucks??? if you drive it until it blows.. most people are looking for drop in and drive... if youre not concerned with reselling.. i'd do a little experiment have some "FUN" and see what the o'l 350 can handle until it goes tango uniform..
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Old 01-05-2006, 02:06 PM
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thanks for the tip.

I will do as you say and run the TH-350 this upcoming summer, then probably go with a Turbo 400. I almost have the car ready after doing some under the hood upgrades this winter. Next winter is when I plan on doing the drivetrain and want to prepare myself and have a plan so that when october 2006 arrives I'm ready to go to work. I would like to sell the TH-350 if I can - why not, but I don't expect to get much for it. If I get $100 that would be great. Is that possible? I can't sell it on ebay because the shipping would cost more than the thing is worth. Maybe a local trans shop would give me some cash for it.
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Old 01-05-2006, 02:34 PM
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Selling

you can brobably sell it for the most on craigslist.. plus you dont get charged a fee to post the ad.. and... the people replying are local.. so they will pick it up...
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