THM-350 or THM400?
Thread Starter
Instructor
Joined: Mar 2012
Posts: 171
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From: Sayreville NJ
THM-350 or THM400?
Which one is better? I thought the 350 came out after the 400, but that confused me a bit
and I am reading that the 350 has slightly higher 1st and 2nd gear ratios's compared to the 400, this means slightly slower acceleration right?
350
1st: 2.52:1
2nd: 1.52:1
3rd: 1.00:1
Reverse: 2.07:1
400
First Gear - 2.48:1
Second Gear - 1.48:1
Third Gear - 1.00:1
Reverse - 2.07:1
and I am reading that the 350 has slightly higher 1st and 2nd gear ratios's compared to the 400, this means slightly slower acceleration right?
350
1st: 2.52:1
2nd: 1.52:1
3rd: 1.00:1
Reverse: 2.07:1
400
First Gear - 2.48:1
Second Gear - 1.48:1
Third Gear - 1.00:1
Reverse - 2.07:1
Last edited by 7vette6; Mar 11, 2013 at 10:48 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The 400 is essentially 'bulletproof'; the 350 is not, unless modified with some stronger parts. Neither is an 'efficient' auto transmission...they are fuel hogs, but they are good for what they are.
If you are going to do much highway driving, and overdrive tranny is a better choice: 200-4R or 700R4. And, as with the 350, they need to be upgraded on specific parts if you are going to throw a lot more torque through them. With the overdrive [high] gear (.67:1), you can do about 20% better on fuel mileage with the same vehicle.
If you are going to do much highway driving, and overdrive tranny is a better choice: 200-4R or 700R4. And, as with the 350, they need to be upgraded on specific parts if you are going to throw a lot more torque through them. With the overdrive [high] gear (.67:1), you can do about 20% better on fuel mileage with the same vehicle.
Racer
Joined: May 2012
Posts: 354
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The man is right the 400 is bullet proof..........>
Racer
Joined: May 2012
Posts: 354
Likes: 0
Something to think about..............>
Arguably the strongest automatic built by the BIG 3 is the 400 turbo 1st, C-6 2nd and the 727B torqeflite 3rd in strength and durabilty. The 400 would take more hp and torque to turn meaning less rearwheel hp. in a BBC or a fully built SBC yes for a more mild street car w/a SBC I would use a R47OO or a 2004R [My street/strip car [T/Buick 3.8 TI-SFI] runs mid 10's @ over 125mph in the 1/4 w/a 2004R, [built] the good thing about the 2004R is if your car has a 350 turbo in it a 2004R will pretty much bolt in w/some mods to the crossmember-w/the 2004R you won't havta cut your driveshaft, w/the R4700 you will> the case is longer. Plus if you drive your car alot at hwy speeds you'll get much better mpg AND less stress on the engine, because the engine will be operating at a lower rpm range. And both above mentioned overdrive units have a good low 1st gear with the benifit of.......overdrive.
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Safety Car
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From: San Antonio TX
Just to be clear, there is a TH200 (metric trans) and TH200-4R. The TH200 is a three-speed very light-duty replacement for the TH350 and would be a disastrous mistake. You did state "overdrive" but if you go junkyard shopping for a TH200, you just might end up with one.
Burning Brakes
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From: Bangor, Northern Ireland