TH350 vs. 700R4
04-13-2012, 11:36 PM
#21
Advanced
I am going through the same process right now. Although I plan on buying a new street strip tranny. I just finished building a stout 350 small block for the Vette which I get to bring to the dyno and fire it up for the first time next week :-) My original plan was to keep this a simple swap, so I was just going to drop in a new TCI super street fighter TH350. But I have also been reading about the 700r4 and a lot of people seem to like the first gear and overdrive. I do plan on leaving the stock 3:07 rear gears for the time being. My machinest is taking a guess that I should be putting out about 425-450 at the crank. The cam I chose requires a 2,500 stall converter. Any opinions on the transmission for my application? Also, I live on an island so the car wont see much highway driving.
04-14-2012, 12:07 AM
#22
Team Owner
Well, if you want good performance, you don't want 3.07 gears in back with an overdrive transmission. You will want 3.36 gears minimum; and 3.55 or 3.70 are better, for a performance build. With a 3.07 axle and in overdrive, your engine will be turning about 1700 rpm at 70 mph. That's not too bad in itself; but at 40 mph, the engine will be lugging badly at around 1000 rpm. And, standing start take-offs will be pretty weak.
Just something else to think about.
Just something else to think about.
04-14-2012, 01:39 AM
#23
Safety Car
I pulled a stock turbo 350 out of a 72 Cutlass, added a "Cheetah manual valvebody", and a 3500 stall and put it behind a built Olds 455 and would pull the drivers front tire off the ground on the street.
Used that trans for several years until I sold the car and never had 1 issue with it.
In the same car I first had a turbo 400 that I literally blew the pan off at a stop light and it had the 32 roller sprag and more clutches in the direct drum.
For the price and condition I couldn't imagine a 200 or 700 holding up very long at all.
If you want a great turbo 350 buy one from www.ptcrace.com in Alabama.
Used that trans for several years until I sold the car and never had 1 issue with it.
In the same car I first had a turbo 400 that I literally blew the pan off at a stop light and it had the 32 roller sprag and more clutches in the direct drum.
For the price and condition I couldn't imagine a 200 or 700 holding up very long at all.
If you want a great turbo 350 buy one from www.ptcrace.com in Alabama.
04-14-2012, 03:59 AM
#24
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St. Jude Donor '05
dead end cruiser Id just leave the T350 in there.
WIth either trans you need to build them up and adjust properly to get longevity. A GOOD trans cooler will always help, heat is the trans' enemy.
After having an OD trans Id never go back to a 3 spd auto or 4 spd.
Deep gears +OD+high strung motor means having your cake and eating it too.
These stock trannies werent meant for the power levels todays cars can put out you have to bite the bullet. $$
Smallblocks can easily make 600+hp now, 500ci BBC is considered small. That stuff just didnt happen much if at all back in the 60s or 70s. Or 80s
WIth either trans you need to build them up and adjust properly to get longevity. A GOOD trans cooler will always help, heat is the trans' enemy.
After having an OD trans Id never go back to a 3 spd auto or 4 spd.
Deep gears +OD+high strung motor means having your cake and eating it too.
These stock trannies werent meant for the power levels todays cars can put out you have to bite the bullet. $$
Smallblocks can easily make 600+hp now, 500ci BBC is considered small. That stuff just didnt happen much if at all back in the 60s or 70s. Or 80s
04-14-2012, 11:17 AM
#25
Team Owner
Neither a stock TH-350, TH-200-4R nor a TH-700R4 will support 500hp and associated torque as originally built. I think that only the TH-400 could handle that power with the original factory configuration for the Corvette.
But, any of the GM auto transmissions can handle that kind of power, if they are assembled with the required 'beefier' parts. And, most tranny rebuilding operations know what those parts need to be. The converter must be capable of withstanding that kind of load, as well.
Pick whichever design unit you wish to use (if you want overdrive, select a 200-4R or 700R4); if not, stay with a 350.
I highly recommed the advantages of an overdrive unit, if you drive at highway speeds for any significant amount of time. This is particularly beneficial if you have 3.55 or higher rear axle ratios.
But, any of the GM auto transmissions can handle that kind of power, if they are assembled with the required 'beefier' parts. And, most tranny rebuilding operations know what those parts need to be. The converter must be capable of withstanding that kind of load, as well.
Pick whichever design unit you wish to use (if you want overdrive, select a 200-4R or 700R4); if not, stay with a 350.
I highly recommed the advantages of an overdrive unit, if you drive at highway speeds for any significant amount of time. This is particularly beneficial if you have 3.55 or higher rear axle ratios.
04-14-2012, 01:49 PM
#26
Advanced
dead end cruiser Id just leave the T350 in there.
WIth either trans you need to build them up and adjust properly to get longevity. A GOOD trans cooler will always help, heat is the trans' enemy.
After having an OD trans Id never go back to a 3 spd auto or 4 spd.
Deep gears +OD+high strung motor means having your cake and eating it too.
These stock trannies werent meant for the power levels todays cars can put out you have to bite the bullet. $$
Smallblocks can easily make 600+hp now, 500ci BBC is considered small. That stuff just didnt happen much if at all back in the 60s or 70s. Or 80s
WIth either trans you need to build them up and adjust properly to get longevity. A GOOD trans cooler will always help, heat is the trans' enemy.
After having an OD trans Id never go back to a 3 spd auto or 4 spd.
Deep gears +OD+high strung motor means having your cake and eating it too.
These stock trannies werent meant for the power levels todays cars can put out you have to bite the bullet. $$
Smallblocks can easily make 600+hp now, 500ci BBC is considered small. That stuff just didnt happen much if at all back in the 60s or 70s. Or 80s
04-14-2012, 02:13 PM
#27
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St. Jude Donor '05
if its not going to see highway speeds why bother
04-14-2012, 06:56 PM
#28
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It was just mentioned, but if you're thinking 700R4 then seriously consider a 4L65E with a controller that monitors throttle and speed. You'll really like how it allows you to dial in the shift points and lockup points so nicely. The example of a 3.08 rear gear says it will be lugging the engine at 40mph. Well, with the computer controlled trans, you just program it to either drop back to 3rd gear or unlock the converter before it begins to lug.
dead end cruiser - you say not much highway driving so maybe it's not worth bothering with overdrive. However, you would still like the versatility of the computer control if you went that way.
I just can't see that. Neither trans would even use 50hp, let alone a 50hp difference.
dead end cruiser - you say not much highway driving so maybe it's not worth bothering with overdrive. However, you would still like the versatility of the computer control if you went that way.
I just can't see that. Neither trans would even use 50hp, let alone a 50hp difference.
04-14-2012, 07:45 PM
#29
Team Owner
Uhh....sorry, but the auto trannies DO absorb around 50 hp, or so. There are a lot of frictional and heat losses via the transmission. But, good transfer of rotational motion to the rear end isn't 'free'. And, you do get the advantage of "torque multiplication" via the torque converter.
While the TH-400 is less efficient than the 350 or 700R4, I'm sure the difference in power usage is nothing like 50 hp (maybe 5-10hp).
While the TH-400 is less efficient than the 350 or 700R4, I'm sure the difference in power usage is nothing like 50 hp (maybe 5-10hp).
