Anybody swap a 700R for a T400 in a mid 70's truck? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

superchevy · 11-16-2004, 06:29 PM

I have a '77 3/4 ton that has a 454/T400 drivetrain. I'd like to swap the T400 for a heavy duty rebuilt 700R I have. Was wondering if anyone on the board has done this. Guess I'll have to move the crossmember back and get a shorter driveshaft. Different yoke? Thanks for the help, SC.

SanitysBane · 11-16-2004, 07:39 PM

yup differnt joke

Jonboy · 11-16-2004, 07:44 PM

I think the 700 has the same yoke as your TH400. You might check it just to be sure. I think the main 3 things are; a) shorter driveshaft, b)move the crossmember (may have to drill a few holes) and c) you will need to swap the TV cable and bracketry to the big block. The aftermarket brackets are pretty reasonable, and seem to work well.

I actually got lucky swapping mine, as I pulled everything out of another 2wd Blazer, so the driveshaft already had the proper yoke and was the correct length. The only other thing I can think of is that you will not be able to hold it down in first with your existing shifter, if you have a column shift. My truck was not blessed with tilt when I got it, so I swapped the column too.

ChevyStepside · 11-19-2004, 12:31 AM

The 700R4 uses the same yolk as a TH350 and is the same lenth as a TH350 with the long tail shaft.. I believe the TH400 is also the same lenth as a 700R4 31 1/2 inches I believe.. If this is true then you will not have to shorten the drive shaft and proabably not even move the crossmember.. The 700R4 also uses the same mount as a 350... Only problem I see you having is the TH400 has the electronic kick down and you will not have the linkage for the TV cable which is Very important on a 700R4.. If not adjusted right you can fry the tranny in a matter of a few miles...

plumbcut · 11-19-2004, 09:26 PM

well I have done something similar- I put a 700r4 into my 77 3/4 ton but its 4x4 and it originally had a th350. If I can be of any help, let me know

pc

SanitysBane · 11-20-2004, 07:35 PM

the joke IS differnt, and the Turbo 400 is shorter than the 700R4, i took some meaurements on that one, and also in the B&M shift kit i got it gave you template so you could make your own mount for the carb linakge, works just fine.

11-16-2004, 06:29 PM	#1
superchevy Got big-block? Join Date: Jul 2000 Location: Austin, Texas Posts: 2,453	Anybody swap a 700R for a T400 in a mid 70's truck? I have a '77 3/4 ton that has a 454/T400 drivetrain. I'd like to swap the T400 for a heavy duty rebuilt 700R I have. Was wondering if anyone on the board has done this. Guess I'll have to move the crossmember back and get a shorter driveshaft. Different yoke? Thanks for the help, SC. __________________ '68 CST SWB factory 396/T400 buddy buckets, a/c, ps, pb '72 Corvette convertible 454/4spd/ac, ps, pb '73 GMC Sierra Grande short wide 454/T400 ps, pb, ac '77 K5 Blazer black on red, 350/T350/NP205 ps, pb, ac all original '78 GMC Sierra Classic short wide 454/T400 ps, pb, ac '72 GMC Sprint SP454. 1 of 38 built. '73 GMC Sprint SP454. 1 of 71 built. '75 GMC Sprint SP454. 1 of 25 built. SOLD! '72 GMC K25 4x4 468/4L80e/NP205 build thread http://67-72chevytrucks.com/vboard/s...23#post4324423 SOLD!'55 Chevy gasser 496/4spd build thread http://67-72chevytrucks.com/vboard/s...96#post4324396

11-16-2004, 07:39 PM	#2
SanitysBane Registered User Join Date: May 2004 Location: Lubbock, Texas Posts: 2,121	yup differnt joke __________________ '96 Nissan Pathfinder '02 Firebird Trans Am. '88 K5 Blazer

11-16-2004, 07:44 PM	#3
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	I think the 700 has the same yoke as your TH400. You might check it just to be sure. I think the main 3 things are; a) shorter driveshaft, b)move the crossmember (may have to drill a few holes) and c) you will need to swap the TV cable and bracketry to the big block. The aftermarket brackets are pretty reasonable, and seem to work well. I actually got lucky swapping mine, as I pulled everything out of another 2wd Blazer, so the driveshaft already had the proper yoke and was the correct length. The only other thing I can think of is that you will not be able to hold it down in first with your existing shifter, if you have a column shift. My truck was not blessed with tilt when I got it, so I swapped the column too. __________________ 1974 Jimmy- 5.3/4L80e/NP241

11-20-2004, 07:35 PM	#6
SanitysBane Registered User Join Date: May 2004 Location: Lubbock, Texas Posts: 2,121	the joke IS differnt, and the Turbo 400 is shorter than the 700R4, i took some meaurements on that one, and also in the B&M shift kit i got it gave you template so you could make your own mount for the carb linakge, works just fine. __________________ '96 Nissan Pathfinder '02 Firebird Trans Am. '88 K5 Blazer

11-19-2004, 12:31 AM	#4
ChevyStepside Registered User Join Date: Jan 2004 Location: San Francisco Posts: 19	The 700R4 uses the same yolk as a TH350 and is the same lenth as a TH350 with the long tail shaft.. I believe the TH400 is also the same lenth as a 700R4 31 1/2 inches I believe.. If this is true then you will not have to shorten the drive shaft and proabably not even move the crossmember.. The 700R4 also uses the same mount as a 350... Only problem I see you having is the TH400 has the electronic kick down and you will not have the linkage for the TV cable which is Very important on a 700R4.. If not adjusted right you can fry the tranny in a matter of a few miles...

11-19-2004, 09:26 PM	#5
plumbcut california fill Join Date: Apr 2004 Location: Sunny So-Cal Posts: 694	well I have done something similar- I put a 700r4 into my 77 3/4 ton but its 4x4 and it originally had a th350. If I can be of any help, let me know pc



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.