THM700-R4 Transmission upgrade?

[ClydesdaleKevin]

Hey guys.  In doing some research on the Blazer, I discovered that its transmission is a 1989 THM700R4...newly rebuilt.

Further research showed that they used this same tranny in a lot of 89 Suburbans with 454s and tow packages.

So my question is, is it a heavy duty enough and rugged enough transmission to use in our motorhome to add an overdrive?

Seems like it would be almost a direct bolt in fit with no electronic controls.

Any problems with this transmission related to motorhome applications?

Thanks!

Kev

[pvoth1111]

No....4L85E @ 685 FPT  or 4L70E @ 495 fpt or 4L65E @ 439fpt.....says JEGS.... plus controllers.....700R4 might last a while but you would have to do it all over again....The Allison 6 spd would be the best...not sure how to make it work with the 454...im sure its possible though....with a Chevy anything's possible....

[cncsparky]

A stock 700R in a 22' C or A, maybe. In your 35 footer, no way!  A heavily modified 700R could be made to work, but would you feel comfortable driving cross country with a specially built tranny. Where would you get service or repair if needed?  A basically stock 4L80e could be worked on anywhere, and is plenty strong for our purposes. 

[ClydesdaleKevin]

That's what I figured after even more research.  Thanks guys!

Plenty strong for the K5...not so much for the Nautilus...lol!

Kev

[Rickf1985]

I originally voted for the 700r4 but I did not realize you had a 35 footer. That would be pushing it. I could build one that would hold up but the shifts would be a little firmer than I would like to see on a vehicle that big. Too much stress on the rest of the driveline. Being a mechanical shift transmission it will shift according to the throttle input, which on that RV is pretty heavy most of the time so the shifts would be rough.

[circleD]

Hey Kev, I know I've mentioned this before in other post but the Allison will fit ANY Chevrolet motor with adaptor plates and couplings. If you research some diesel forums you can find these. Do NOT get the Generation1 version 2000-02.5 because those had bad 1st gears and reverse plus the fly wheels cracked. I've been thinking of putting the complete drive train of a 2500HD duramax in mine in the distant future  . Just a word of advice about UPGRADEING is taking it to a garage to get work and they scratch their heads with no clue.