Swap 2004R to ? 350/400

Moe · Posted: Tue Jan 20, 2004 5:31 am Post subject: automatic transmission bigot :)

My $0.02 worth...

I had a THM200-R4 in a chevy caprice behind a mild 305 TBI with a 2.73 rear end. It could not even spin the tires (205/75R15's). Nonetheless, the 200R4 burned out. They're known to be weak transmissions. The transmission shop had about two dozen of these in the 'backyard'... no one wanted them or wanted theirs to be rebuilt.

So I had a 700R4 put in (painless swap, mostly). I was told they're rather large transmissions and can be quite reliable (or quite buggy if factory from pre 87). Mine was rebuilt about 9 months previous (to 2002)... my brother still had the $1200 in receipts and I recall when his Impala died due to the failure (when it was a factory 700R4 from '85).

The 700R4 died too, about 4 months later in my caprice.

Then I had a THM350-R3 installed. Used, old... I simply swaped filters, threw some magnets in the pan, and dropped in some new oil.

Solid as a rock. The problems associated with a 200R4/700R4 to a 350R3 swap seem to be transmission cross member support and the driveshaft is a different length. Otherwise, it bolts right on to a 305 or 350 block (same thing, mostly).

Every GM vehicle I've had with a 200R4 or a 700R4 has suffered a failed transmission. A 350R3 has never failed me. If I buy a GM vehicle and it's not a THM350R3 (or 400R3) ... I expect to blow out the transmission and replace it with one that I trust. Namely, a GM THM350R3 or a THM400R3.

I'm not saying the GM THM350R3 (or 400R3) is indestructible, I'm just saying it's better than any GM overdrive transmission. (I'm expecting many retorts and I anxiously await them... can a 700R4 be stronger than a 350R3... or even a 400R3?).

So that's my 2 cents worth. Keep the change. Smile

theelcaminofactory · Posted: Tue Jan 20, 2004 5:36 am Post subject:

guru54...If it does need to be rebuilt and you plan on selling it, you won't get back the money/time you put into it to rebuild it. If you want to do it just to gain some knowledge or experience, then thats different. The 350THD is readily available at any boneyard (cheap). If I needed a 350THD, I would either buy an aftermarket professionally remanufactured trans like TCI or rebuild my own. And Moe...I agree, I think the older 3speed transmissions just seem to be made better and last longer. Recently bought a wrecked 3/4 ton Chevy pickup just to get the 350 4 bolt main running motor and 400THD...$250. Swapped the 400THD into another pickup in an afternoon and it works fine. Thats $250 for a 350 4 bolt main running engine and a 400THD trans.
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Tommy · Posted: Tue Jan 20, 2004 8:28 pm Post subject:

The first 200s were real weak but the later ones were pretty good. From what I have read the 200s were improved to work with the GNs & MC SSs.
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