What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

need help, tranny swap, 700r to th400

irishraptor87

irishraptor87

1/2 ton status
Joined
May 25, 2006
Posts
141
Reaction score
0
Location
ct
im putting a new motor in my burb, and i decided to upgrade to the th400 from my 700r

i have been searching and figuring out what i can, but i think i need more info...

so the 400 has an electric kickdown, not bad, im going to prolly end up picking up this part gm# 1242101, which is the switch that goes behind the pedal to make it switch over, fairly simple, i can do that

on the other side of the tranny, there are what look like 2 ports for cooler lines, i can run those on my own.. easy

then theres the dipstick, which i got with the deal, so that can be taken care of

but next to the dipstick, sticking out horozontally is another hole... i dont know what this is honestly, i would assume it is the vaccume that controls shift points, i have never had a 400 so im not sure, is there supposed to be a fitting in this hole, and how should i run i line, i got nothing in the deal having to do with this, do i need a modulator in-line to my carb

lastly, he didnt have the flexplate to this, what flexplates are compatable to this tranny, i have a spare one from a 83 th350, would this work, id like to save some money

all help is greatly appreciated!
cory
 
im no tranny expert, but that horazontal hole may be a vent hole. i know the 700R4 has one, but it has about a 2in pipe that sticks out of it. nothing connects, its just a vent. someone here will correct me if im wrong.

as for the flex plate, i really can tell ya.
 
The 400 has a vacume modulater that should be in that hole if its the one IM thinking of. It should have a bolt hole right next to it. (towards the front of the tranny). It installs with a clip that bolts next to it simular to a distributor. The modulator will need a vacume line ran to the intake. And, as far as I know, the flex plate for th 700r4 should be the same. But, I would check with a parts house on that one to make sure. The cooler lines should be the same as the ones on your 700 as well. They should just screw right in.
 
The flex plate was the same on my 86. My cooler lines were also the same. The crossmember is different.
This is what the vacuum modulator looks like.
bmm-20234_m.jpg
There was a piece of steel tubing that goes from the modulator up over the back of the engine to a tee in the top of the intake, behind the carb. This tube had a short piece of rubber vacuum hose on both ends. The tee should already be in place on your engine. Just hook the vacuum modulator line into one of the vacuum hoses that come off the engine tee. Use a tee you buy at the parts store for this.

Did you get the transfer case with the trans, or are you going to use yours? Yours may not work without different adaptors and/or shaft changes.

Mike

bmm-20234_m.jpg
 
I am Installing a th400 in place of my 700r4 this weekend. Everything everyone has said so far is correct. To add though, Your tcase from your 700r4 will not work with the th400, unless you change the end spline shaft.
My th400 came with a 208 case so I have no problems there.
Hopefully i should be good to go. I will post my work after i am done, maybe a good write-up for the tech section.
 
i had found out about the 400 using a 32 spline and the 700 using a 27 spline, so i made sure to get the tranny with a transfer case
 
You must log in or register to reply here.

Latest Posts

Top Bottom