Thread: TH350 to 700r4 swap

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thinking about going to a 700r4 trany,keep getting conflicting info from different people.will the 700 go in the same spot as the 350?same size,same cross member bolt patern,same overall length? any thing I,m overlooking?

I believe you will have to move the crossmember and shorten the driveshaft length. If you want to be able to to manually shift it into L, you will have to modify the shift gate in the steering column. I did mine and it was pretty easy.

Keith

The trans mount is in the same place, but the drive shaft will have to be shortened btwn 1 1/2" to 2". Unless of course you have a long tailshaft 350. Then, all bets are off and you're on your own.

There are actually three “sizes” of TH350 – short (6”), medium (9”) and long (12”) tail shaft. The key measurement is the overall length, i.e., from the lip of the bell housing (where it bolts to the engine) to the lip of the tail shaft. The short TH350 measures; 27-11/16”, medium is 30-11/16 and the long is 33-27/32”.

700R4 in all but Corvette applications measure 30-3/4” The Corvette is (for some strange design/engineering reason) 29-7/8”.

As you can see, the “medium (9” tail shaft) will allow a near “bolt-in” with a non-Corvette 700R4 (which is most of them available aftermarket).

The TH350, 200R, 700R and 4L60 all use a 27 spline yoke.

Not a real difficult swap – but I’d recommend a visit to the boys at “Bowtie Overdrive” as this is all they do and they do it very well: Bowtie Overdrives

Let us know what you decide!
Glenn

I had to move the cross member, and issues with the drive shaft....I don't want to get into it...

All I can say is I like what Sexton said, but I would just match it up best ya can...

Mine was a 30 Spline, it mated to a ZZ4 350 GMPP crate engine, the Tranny was from TCI...>>> I WOULD NEVER BUY A TRANNY FROM THEM AGAIN
But don't let that stop you from using a 700R4 tranny,... I have one that is working in my truck, but I don't know that I will ever feel confident going on a long trip...

While I had my issues with the TCI tranny, I had a local transmission shop rebuild a core, not once, but, Twice, on two separate occassions I had to have a replacement tranny, so I went with a Used and Abused rebuilt core $1500 installed....with this TH350, it rocked, seemed to be a better tranny over the brand new one I had break down 2 times now...

The TH350 is a great tranny, just that folks want the OD, or 4th Gear (.70 over) trying to get a little fuel economy.... and that the 700R4 has a really low First Gear, almost too low...

If you have to have the drive shaft shortened, or lengthend, or a longer yolk going into the tranny etc...

Hope things work out for you...
Good luck.