I am thinking of swapping in a Th700 into my 89 3/4 ton Suburban, which has the Th400/241 combo. Has anybody done a similar swap or know if it’s all that difficult? I know there are differences between the two such as the output shaft size. I just need overdrive. It sucks making a 9 hour drive without it. I know gear vendors has their overdrive, I really think the 400-700 swap is more cost effective and I will have better results.

Thanks for any info.

Mat

can be done.
you have to change the input on the transfer case and use a different t-case to trans adapter. also, the shifter, set up some sort of lockup harness, converter, and some other small stuff.
make sure you get a th700 between 1988 and 1992, those were the best years.



oh, and welcome to the club, newbie fawker! :flipoff2:

i would use a 4l80e tranny in place of th 400 because they are equal in strenth the th700r4 is weak it is used in S10's and 1/2 ton trucks, you really don't want it if you have a big block unless you have it built by tci or some other hi performance tranny builder.

Man I would love to have that Th400/241 combo. It's driver side drop for that year isn't it?

all solid axle GM's are passenger drop.

a 700 does not have to come from tci or a high performance shop to be built right. and they do come in suburbans as well.
the early 700s had problems, but they are a good trans and do not require a computer to run them, unlike the 4l80e.

a 700 does not have to come from tci or a high performance shop to be built right. and they do come in suburbans as well.
the early 700s had problems, but they are a good trans and do not require a computer to run them, unlike the 4l80e.


what about the torke converter, doesn't the computer control it?

wired correctly, the convertor clutch will activate in overdrive as soon as the trans hits fourth gear. its not electronic on a 700r4, but rather activated by a solenoid through hydraulic pressure.

Again, Wired correctly, not neccesarily by the factory.

I know the 700 is non-computer controlled. Generally its wiring gets tapped into the brake circuitry. If I was to convert, I would need the TV cable and the wiring for the TCC (torque converter lock up), as the TH400 has a non-lock up converter, well at least on my Suburban it is. I am probably going to forgo the 400-700 swap. If I do anything I will go with a Gear Vendors OD. Someone mentioned the L480 E swap, which is a great idea, except it would cost way more because it needs a stand alone computer and the trans itself is expensive. Thanks for all the tips.

Mat

the torque converter lockup in a th700 is controlled by a few different functions, but is activated by the vehicle computer.
painless makes a simple harness that eliminates the computer.
basically, for the converter to go into lockup mode, the vehicle has to be moving above 42mph, in 3rd or 4th gear, brake pedal can not be applied, and vacum has to be about 17lbs or higher.
converter lockup basically eliminates all slippage in the converter, thereby reducing the heat being produced in the converter and dropping the engine rpms a few hundred, giving you better milage.