Tranny Questions

[REW_388]

I have a 87 4x4 3/4 ton with the tranny going. It currently has a 400 tranny my question is whether or not I can put a 350 Turbo in it, short shaft or long shaft, and if so what will I have to change. Oh and it has a small block 350 in it.

[old Rusty C10]

a 350 will bolt right up but its not as strong a trans. You want a long tail and the driveshaft will prolly need to be either lengthened . Im not sure if you will need the yoke from the th400 or not and you will have a couple of other differences that are n ot hard to change over. In all honesty id just rebuild the th400

[glock35ipsc]

Don't get mixed up with any tranny that......... oh wait, you mean transmission?

Well then, ....... The driveshaft lengths may be different depending on the replacement trans, you will need to hook up the TH350's kickdown cable at the throttle body, probably move the crossmember, I'm not sure about the TH400's transfer case mating up to a TH350 (I'm not a 4x4 guy).......

But I'm with Bob, keep a TH400 in there. No point in going with a weaker one. Why the desire to go to a 350?

[MR .T]

im pretty sure the case will be the same. A 4x4 trans is different from a 2wd.

[REW_388]

Well the reason is I can find a 350 easier and that extra gear... I need to lower my rpms at high speeds cuz I am getting blow by at about 60mph and up and I don't really have the money to rebuild both motor and tranny right now and since its just a work/farm truck I didn't think the weaker tranny would be that huge of a difference.... but idk I'm not a transmission guy haha

[joe231]

Originally Posted by REW_388

Well the reason is I can find a 350 easier and that extra gear... I need to lower my rpms at high speeds cuz I am getting blow by at about 60mph and up and I don't really have the money to rebuild both motor and tranny right now and since its just a work/farm truck I didn't think the weaker tranny would be that huge of a difference.... but idk I'm not a transmission guy haha

the 350 and the 400 are both 3 speeds
you can get a 350 with a lock up converter, but it will only drop around 200RPM, and technically it isn't another gear. If you want a 4 speed you will need a 700R4, 4L60E, or 4L80E the latter 2 will need a computer to operate.

[Mr.Chevy4x4]

The turbo 400 has a 32 spline output and the turbo 350 and 700r4 have 27 spline output. Neither a turbo 350 nor 700r4 will bolt up in place of the turbo 400. If you want overdrive you will need to find a complete 700r4 with the NP208 transfer case. If you buy the complete unit it will bolt up. Your current transfer case is a NP208. Your drive shafts will have to be lengthened/shortened as the 700r4/208 combo is longer than the 400/208. GM transmission/transfer case swaps are never as straight forward as they should be.

Let me know if you have any questions.

Mike

[REW_388]

Well then my next question (might be a stupid one) is can a 2 wheel drive 700r4 have a transfer case mounted to it, I heard 2 wheel drive transmissions cant be made 4, but I have an extra 700r4 sitting around

[clinebarger]

Originally Posted by REW_388

Well then my next question (might be a stupid one) is can a 2 wheel drive 700r4 have a transfer case mounted to it, I heard 2 wheel drive transmissions cant be made 4, but I have an extra 700r4 sitting around

4WD 700R4s has a diffferent output shaft than a 2WD 700R4. The transmission will have to be torn down to install the 4WD shaft.

In my opinion a 700R4 is a poor choice for a 3/4 ton truck if you tow or do offroading with it.

[Mr.Chevy4x4]

Yes it can be made to work in your 4x4, but may not be worth the hassle. The output shaft in the transmission would have to be changed. The 2wd and 4wd transmissions had different output shafts. You will also need a 700r4/NP208 transfer case adapter, and a 27 spline input NP208 transfer case. Your transfer case has a 32 spline input.

[REW_388]

Well that answers all my questions! Well ones I have for now anyways haha thanks everybody its been very helpfull