tranny swap question- T700 to T400)(TH375)? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**crossy** · 11-23-2007, 12:28 PM

I’m trying to help out an older gentleman who uses his 85 Chevy C10 for scrapping and recycling to supplement his income. He has 7 kids at home too! This 400 will be much better for him in the long run. He has very limited mechanical skills but has a friend who is going to help him cause I don’t have that kind of free time. I will verse him on the converter engagement issue and told after it is in and filled with fluid I could adjust whatever might need it.

Anyway I have one of those funky TH400 trannys that came out of an 86 C10, I didn’t remove it or I would have saved and marked all the supporting componets. Some people call these things TH375’s ,but it is a th400 with a small output. It appears, without measuring, that this 400 will bolt right in where his dead th700 is. I thought that was the reason GM finally did this was so that they can use the same driveshaft and crossmember to mount either tranny depending on options of the truck. Saying we want to put this in his truck, will it bolt right up to the existing crossmember by just moving it to different holes in the frame?? I have no rubber mount on the T400 so I assume it is different from the T700?? What did the T400 use for kickdown in the late 80’s?? was it the electric solenoid??. any useable info appreciated.

AirMale · 11-23-2007, 05:21 PM

Easy swap... holes are allready on the frame for x-member. Electric kickdown(pick&pull) is on the pedal and gets one wire to panel and one to the spade on tranny. Run one vacuum line from tranny to carb for upshifts. Easy!

**crossy** · 11-23-2007, 06:28 PM

whadda you know about tranny swaps!!!!

thats right , i even have one of those solenoids somewhere in this mess with the wires, HMMMM

I did know about the modulator vacuum line.But thanx for reminding me.

MylilBowTie · 11-23-2007, 11:17 PM

If the truck is a long bed it should fit right in. The th375 has the same output shaft as a th350, 700r4 and 200r4. Length also should be right there with the th350 9in tailshaft. I have swap a 700r4 to a th350 with 9in tailshaft no problems. The th375 should go without a hitch.

The kickdown switch on comes on at wot. Shifting from 3rd gear into 1st gear at low speeds. The transmission will down shift on its own without the kickdown switch. Just not the 3rd to 1st.

11-23-2007, 12:28 PM	#1
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	tranny swap question- T700 to T400)(TH375)? I’m trying to help out an older gentleman who uses his 85 Chevy C10 for scrapping and recycling to supplement his income. He has 7 kids at home too! This 400 will be much better for him in the long run. He has very limited mechanical skills but has a friend who is going to help him cause I don’t have that kind of free time. I will verse him on the converter engagement issue and told after it is in and filled with fluid I could adjust whatever might need it. Anyway I have one of those funky TH400 trannys that came out of an 86 C10, I didn’t remove it or I would have saved and marked all the supporting componets. Some people call these things TH375’s ,but it is a th400 with a small output. It appears, without measuring, that this 400 will bolt right in where his dead th700 is. I thought that was the reason GM finally did this was so that they can use the same driveshaft and crossmember to mount either tranny depending on options of the truck. Saying we want to put this in his truck, will it bolt right up to the existing crossmember by just moving it to different holes in the frame?? I have no rubber mount on the T400 so I assume it is different from the T700?? What did the T400 use for kickdown in the late 80’s?? was it the electric solenoid??. any useable info appreciated. __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

11-23-2007, 05:21 PM	#2
AirMale Senior Member Join Date: Jan 2003 Location: Atlantic City, NJ Posts: 1,073	Re: tranny swap question- T700 to T400)(TH375)? Easy swap... holes are allready on the frame for x-member. Electric kickdown(pick&pull) is on the pedal and gets one wire to panel and one to the spade on tranny. Run one vacuum line from tranny to carb for upshifts. Easy! __________________ 86 SWB 9.0 LITER T-400-OD 4.11 eaton-4/5 drop Best 1/4 12.51 @112mph no traction

11-23-2007, 06:28 PM	#3
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	Re: tranny swap question- T700 to T400)(TH375)? whadda you know about tranny swaps!!!! thats right , i even have one of those solenoids somewhere in this mess with the wires, HMMMM I did know about the modulator vacuum line.But thanx for reminding me. __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.

11-23-2007, 11:17 PM	#4
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	Re: tranny swap question- T700 to T400)(TH375)? If the truck is a long bed it should fit right in. The th375 has the same output shaft as a th350, 700r4 and 200r4. Length also should be right there with the th350 9in tailshaft. I have swap a 700r4 to a th350 with 9in tailshaft no problems. The th375 should go without a hitch. The kickdown switch on comes on at wot. Shifting from 3rd gear into 1st gear at low speeds. The transmission will down shift on its own without the kickdown switch. Just not the 3rd to 1st. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI



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