TH350, TH400, or TH700 - Which one's better? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 08-06-2000, 06:25 PM
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TH350, TH400, or TH700 - Which one\'s better?

Well, I fear that I am once again going to have to probe the wealth of knowledge that's available here on ORC.

I think I am going to have to run an automatic in my truck until next year before I can convert it back over to the SM-465 that came stock (don't ask me why the previous owner put a TH350 into the truck).

I have the following transmissions that I can put in -

TH350/203 - in the truck right now but ready to come apart. Slips when in gear from time to time and occasionally seems to miss shifts. I know a guy that will rebuild it for about $200.

TH400/203 - It's in decent shape and works fine. Not sure how much abuse it's seen. Is a TH400 a 3 speed or a 4 speed???

TH700/208 - This trans is definately the best unit out of the 3 in terms of functionality, but it's mated to a NP208. I think I'd have to do some custom work to get it to fit - I think a 700R4 is about 2.5" longer, and I know I would have to modify the existing driveshaft in the truck as it's a bolt on type. The 700 has a splined shaft that fits into the back of the 208.

So, which transmission will be the best in terms of durability for the short term (1 year max until I can acquire and install an SM465)? The transmission is going into my 84 3/4 ton with a pretty much stock 350 and 35's. The truck isn't going to be a daily driver until it's all done, the way I want it...

Thanks for any help and/or opinions you can offer. I can build a truck but don't know much about auto trannys!

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post #2 of (permalink) Old 08-06-2000, 08:06 PM
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Re: TH350, TH400, or TH700 - Which one\'s better?

If your only going to have it in for 1 year then I would go wih the 400 because its the strongest tranny you have and it sounds like it should work fine, and you didn't say anything about doing driveshaft mods. It is a 3 speed If you need OD I'd go with the 700 but its sounds like you wont so jsut stick with the 400

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post #3 of (permalink) Old 08-06-2000, 09:39 PM
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Re: TH350, TH400, or TH700 - Which one\'s better?

since it's not going to be a daily driver, I'd spend the $200 on the 350...the 400 is longer than the 350, but matching the 203, wouldn't be much of a hassle to swap...a driveshaft for the 700/208could be had from the yard for cheap...rebuilding the 350 would give you a tranny you know is good (dependable)...I'd rather dance with the devil I know...I know others have more knowledge on this...good luck...

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post #4 of (permalink) Old 08-07-2000, 10:12 AM
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Re: TH350, TH400, or TH700 - Which one\'s better?

The T400 is a 3speed auto, and is by far the strongest most dependable automatic tranny GM ever built! [img]/wwwthreads_images/icons/smile.gif[/img]
I would measure it, and see if it would be a direct swap for the T350, without re-cutting the driveshaft, if it will, I would use it. If it won't, then just rebuild the T350!
Forget about the 700[img]/wwwthreads_images/icons/frown.gif[/img]! to have a healthy 700 you have to spend well over $1000, and then since most people never use the OD, you end up with basically a T350 again!

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post #5 of (permalink) Old 08-07-2000, 10:57 AM
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Re: TH350, TH400, or TH700 - Which one\'s better?

<font color=purple>I'm with Scoob - if the TH400 is functional & is only going to be temporary anyway, only use it if you can do so w/o driveshaft mods. Otherwise, you can redo the TH350 pretty cheap & truth be told, that's still a damn fine tranny.</font color=purple>


post #6 of (permalink) Old 08-07-2000, 11:33 AM
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Re: TH350, TH400, or TH700 - Which one\'s better?

It sounds like the TH400 is going to be the ticket for the short term. I have the matching driveshaft so it should be a pretty easy swap assuming pinion yokes are the same size on the rear differential.

I would rebuild the TH350, but the truck is only going to see occasional use until I get her set back up with an SM465. I think the TH400 has a little bit of life left before it needs a rebuild anyway.

Thank you much for the tranny info! I'm clueless when it comes to automatics.

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