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Old 03-16-2003, 08:33 PM
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Post TH 350 vs TH 400

I just wanted your opinion on which tranny was better overall? Which one can hold more horsepower? I got my 350 4 bolt and am doing a rebuild this summer. I would like to have about 450 hp. I just want your opinion on which one would work best, or is this just an opinionated question? Thanks for your help. Bill

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Old 03-16-2003, 09:29 PM
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the 400 is a stronger tranny, but heavier, often as in the TH350, the sprag is the weak link.
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Old 03-18-2003, 07:28 PM
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The 400 gearing is worse than the 350 but the 400 is a bit stronger, horsepower isnt going to hurt it the torque will be the determaning factor, rember ricers can get 500+ hp out of 4 bangers but they still are slow....er than a good muscle, I cant talk much I dont wanna race most for the chance of them wining and then what do you do?????
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Old 03-18-2003, 07:33 PM
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go on google and look up chevy tranny ratios or some wording to that effect you can check the ratios and decide that way, the 400 will hold a gear longer before it shifts but wont accel. as fast as a 350 with its steeper gearing better yet is the 700r4 that has lower first and second gears and a .70 over drive, weaker yet unless built right, the 200 4r has gearing closer to the 350 but has a better overdrive yet .68 or so but its 7 or 8 in longer and I dont know how strong they are.
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Old 03-19-2003, 02:04 AM
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200r4 's are even weaker than the 700 's
I'm trying to get a not too bad condition 700 and rebuilding it myself with heavy duty parts for my 400lb/ft 300 horse 350 (currently a TH-350)
I like the idea of closer 1st and 2nd AND an overdrive.

I've seen re-build kits for 700R4s rated upto 800 horses, so 450 should be no problem.

[ March 19, 2003: Message edited by: andybird ]</p>
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Old 03-21-2003, 12:49 PM
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personally out of the original 2 i would get a 350 built right. they are comming around with so many gears . transbrakes and sprags now a days it makes the big 400 useless. a 350 uses less torq and hp to turn over a 400.

but out of a 200-4r and a 700r4 i would go with a properly built 200. they use less hp and torq and have a better 1st to 2nd gear change. the rpm drop in the 700 would require alot of torq to pull it back up to a motors rpm range at that change.
plus a properly built 200-4r can easily take 1200hp , even more. dont you see alot of grand nationals running in the low 9's using 200's? they are a better choice.
plus a 200-4r is the same length as a 350. big plus again.

oh and im running a hughes th 350 on a 550 hp small block. so they can definately take the abuse.

[ March 21, 2003: Message edited by: Necro ]

[ March 21, 2003: Message edited by: Necro ]</p>
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Old 03-21-2003, 01:13 PM
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All advice so far is good. Each tranny has good and bad points. TH350 was designed for passenger cars/sports cars so has close gear ratios, low internal power consumption, pretty good power handling capacity. TH400 was built for mainly trucks so gear ratios are wider spaced, can handle more torque and internal friction is higher but in a truck, who cares?

7004R and 200R4 get a bad rap for reliability but I have rebuilt all 4 and the latter two are altogether as robust as the former two. Sure there are weak parts like a coupel of nylon thrust washers but the TH350 and TH400 have weak parts also. All can be replaced with better parts and none cost the national debt to modify. Main problem with the OD trannys is that the TV or detent or whatever you call it must be set much more precisely than the older types. Can't set the throttle link by ear, must use a pressure gauge and set it over the entire throttle range to precise angular displacement settings.

That being said, the ODs are great trannys. They can be made to handle 1000hp with no more effort than it takes to do the same to the 350/400 series. The 200 has a lot of advantages over the 700 as Necro points out. I think it must have gotten the 'weak sister' reputations from the hot rod press but you know how reliable their opinions are. Probably the only 'weakness' in the 200 is that it fits Chev and BOP while the 700 is a Chevy only verison. Thus the 200 MUST be inferior? Since I can get a 200 and build it for less than half the cost of the more in-demand and sexy 700, give me the 200 all day every day!
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Old 03-21-2003, 11:28 PM
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Hey necro you only got one problem with the tranny length thing the mount on the 200 is 8 in farther back,just figured id mention that. the truck th350 is the same length as the 700 the 400 i think is a all together a diff. length. the 700 will need a shortened drive shaft by about 2 and 11/16 I think from what Ive read. And you have to move the mount back one set of mount holes. Also the 700 has deeper 1st and 2nd gears compared to the 200 so if you need more top go 200 if you want more low end and good top 700.
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Old 03-22-2003, 12:43 PM
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go to a local trans shop and ask if they build them up for racing applications.most of the time a 350turbo is cheaper to build and is lighter.with the right parts they can handle lots of power.
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Old 03-22-2003, 03:18 PM
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All this talk about the vast difference between the Turbo 350 and the Turbo 400 gear ratios are BULL.

A T350 is 2.52 low
A T400 is 2.48 low

A T350 is 1.40 in 2nd
A T400 is 1.48 in 2nd

Both are 1.00 in high

You cannot detect the difference in ratios in a street car. A Turbo 400 does take away a few more HP than a Turbo 350 because it is larger, and more heavy duty. The Turbo 400 will stand 500HP all day long without failure. That's stock.


The ratios listed above are stock GM ratios, not aftermarket.


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Old 03-22-2003, 05:54 PM
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I agree with Deuce Roadster. They put the TH400's in the early big block Camero's for a reason. They're (almost) bullet proof.

The ratio differences are Mox Nix.

For anything over 450hp, A TH400 and a Dana60 are the only way to fly - street OR strip.
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