CUCV TH400 swap to 700R4?

[KidKodiak]

My 1984 M1009 CUCV has a TH400 trans and 3.08 axles. My super awesome uncle is giving me a complete drivetrain for free. So with 3.08 axles, 700R4 from a 6.2 Diesel Suburban, and 31x10.5 tires is the first set up.

Any words of wisdom, advice, or anything I should know/consider?

I've also read CK5 and Steel Soldiers forums. I've only posted on here because while the others are good, you all are consistently more accurate. So you to all who've responded to my other posts.

[Robyn]

The 700R4 will fit.

This said, with the 3.08 axles you will not really gain anything with the 700R

The 700R is nowwhere near the tranny that a Th400 is.

The best bet would be to keep the TH400 and not waste the time doing the swap.

The final drive ratio with the TH 400 and the 3.08s will be nearly the same as the 700R4 would be using the 3.42 gears that were common with the 700R4.

The only advantage would be the real low 3.06 1st gear or the 700R

To get good reliability from a 700R will cost some serious $$$$ ($2K) on a build.

The TH 400 in stock form will outlive a 700R by many times over.

The 6.2 with the TH400 and the 3.08 gears will get great mileage.

Power wise the tall gears will kill things a bit though.


Just my 2 cents worth.

Missy

[87max]

What is it your trying to gain by the swap? As Robyn said only advantage of 700r for you would be first gear, as the 3.08 gears are already basically overdrive. Lotta work for little gain.

[KidKodiak]

I figured the 700 with the 3.08 would be a little too much on the highway. But my only reason for considering the swap, as you mentioned, was the lower first gear.

My thought was just so I could be easier on the pedal as I accelerate from a stop sign/light. But considering the winter conditions and the low end torque of the 6.2, it might be better to have the higher first gear.

I know the cheapest and easiest option for my acceleration would be to go to smaller tires... say 235/75/15.

Any thoughts on downsizing the tires? I don't want to stand still while my tires spin in the snow either.

Thanks again, Missy and Max.

Ryan

[KidKodiak]

I've also read CK5 and Steel Soldiers forums. I've only posted on here because while the others are good, you all are consistently more accurate. So you to all who've responded to my other posts.

Thank you to all who've responded to my other posts. And this one too.

[87max]

I'd drive it as is and decide after a while. Short of doing heavy hauling/towing or for performance pulling/drag I wouldn't sweat it. Change would be very very minimal for the amount of work.

[87max]

And throw a few hundred pounds in the back for winter!! I used to run about 800 when I plowed, after I put a locker in I didn't even use 4wd most of the time.

[Robyn]

To sum it all up.

The 700R is a fine tranny (if built right) for a 1/2 ton light duty pickup and or 1/2 ton Burbs/Blazers (Tahoe) that are used as people movers.

The internal components of the 700 are quite small as compared to the TH400.

The input drum on the 700R is aluminum with the input shaft pressed into the aluminum splines or the drum.

The input drum holds almost all the clutch packs and they are about 1/2 the physical size (clutch discs) of the parts in the 400

There are many tranny builders that advertise 700R4 trannies that will hold up to 475Hp and 375lbs of torque.

The price tag on these gear boxes is a very health bite from the checkbook.

These run in the $3000 range.

The last 700 I built for a diesel Blazer cost me (wholesale with me doing the bench work) about $1600.

A stock 400 can be thrashed something aweful and live to tell about it.

Enjoy the rig.

Missy