swapping out a 700r4 with a 400

mittan88 · 02-26-2006, 06:59 AM

I have a 1988 chevy pickup and the motor has 275000 miles on it and has gone thru 3 transmissions I want to put something alittle more bullet proof as far as transmissions go i have a freshly rebuilt 400 with shift kit and everybody. can I swap this into my pickup and with minimal cobeling. any advice will help im sure im not the only person sick of these weak link transmissions. thank you

mrjohnwayne · 02-26-2006, 06:31 PM

the tranny will bolt up but you'll have to change your driveshaft. And im not sure but you might have to relocate your x-member.

shopratles · 02-27-2006, 07:19 PM

Wait though, not so fast. That TH400 has electronic kick-down that your truck isn't wired for. There is more work there than you know. Why are you having problems with 700R4's? What I mean is who is rebuilding these for you? With regular/decent service you should be getting at least 150,000 miles out of them. I would check around and get a good rebuilder to do the 700R4. Just my opinion though.

Good luck.

mrjohnwayne · 02-27-2006, 07:32 PM

You are right Shop. But all it is, is a switch that mounted under the dash that would be actuated whenever yout pedal was pushed so far. You don't need the switch. You can downshift manually. However if you feel more comfortable running with it than is a simple add-in. It is a single wire that runs to the tranny.

mrjohnwayne · 02-27-2006, 07:34 PM

Also if you wanted to build a stout TH-400. With a decent shift kit, and a few other tricks you can actually block off the Detent solenoid and believe you me it is a "noticable" shift.

mittan88 · 02-28-2006, 05:12 PM

I have an 88 extended cab with a full 8 ft. bed so it comes with the carier bearing and two piece drive shaft. so is it the size of the yoke that differs or is it the length? because I got the trans out of a late 80's pickup. the kick down thing i can handle so I'm not too worrried about that but I would like to hear about the better shifting thing from john wayne.

mrjohnwayne · 02-28-2006, 07:25 PM

They Yoke on the 400's bolts to the tailshaft of the transmissopn. You'll have to lengthen the first half of the shaft, along with reconfiguing the yoke situation. As far as the shifting goes I don't think you would want to run a daily driver with what I mentioned before. From the looks of it you already have a tranny that'll serve that purpose shift wise. hope this helps

mittan88 · 03-01-2006, 03:52 PM

i meant to ask if the spline is the same on the 700 as the 400 or will I have to change it the 400 is the same length as the 700 so the length thing will not be a big issue as far as a daily driver it won't be so I would really like to hear your shift thing. I want it to snape your head off when it shifts. thanks and hope to here from you,

mrjohnwayne · 03-01-2006, 04:57 PM

With a decent shift kit, you can block off the detent solenoid (please don't hold me to this its been a long time, but any tranny shop that builds performance trannies can help) take the springs out of the 2nd gear govenor, and block off the 3rd gear govenor. To do so you remove the c-clip that holds the govenor in place. Do not remove the govenor. Add washers around the shaft until no movement occurs whild c-clip is in place. I can't remember if that is all. It's been a few years since I last rebuilt mine. As for the spline I'm pretty sure the 400 is bigger. As I said it's been along time since i've messed with any automatics. Hope this helps.

02-26-2006, 06:59 AM	#1
mittan88 Junior Member Join Date: Feb 2006 Posts: 5	swapping out a 700r4 with a 400 I have a 1988 chevy pickup and the motor has 275000 miles on it and has gone thru 3 transmissions I want to put something alittle more bullet proof as far as transmissions go i have a freshly rebuilt 400 with shift kit and everybody. can I swap this into my pickup and with minimal cobeling. any advice will help im sure im not the only person sick of these weak link transmissions. thank you

02-26-2006, 06:31 PM	#2
mrjohnwayne Senior Moderator Join Date: Apr 2005 Location: Texas Posts: 3,722	the tranny will bolt up but you'll have to change your driveshaft. And im not sure but you might have to relocate your x-member. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

02-27-2006, 07:32 PM	#4
mrjohnwayne Senior Moderator Join Date: Apr 2005 Location: Texas Posts: 3,722	You are right Shop. But all it is, is a switch that mounted under the dash that would be actuated whenever yout pedal was pushed so far. You don't need the switch. You can downshift manually. However if you feel more comfortable running with it than is a simple add-in. It is a single wire that runs to the tranny. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

02-27-2006, 07:34 PM	#5
mrjohnwayne Senior Moderator Join Date: Apr 2005 Location: Texas Posts: 3,722	Also if you wanted to build a stout TH-400. With a decent shift kit, and a few other tricks you can actually block off the Detent solenoid and believe you me it is a "noticable" shift. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

02-28-2006, 05:12 PM	#6
mittan88 Junior Member Join Date: Feb 2006 Posts: 5	re:john wayne and the shiftt I have an 88 extended cab with a full 8 ft. bed so it comes with the carier bearing and two piece drive shaft. so is it the size of the yoke that differs or is it the length? because I got the trans out of a late 80's pickup. the kick down thing i can handle so I'm not too worrried about that but I would like to hear about the better shifting thing from john wayne.

02-27-2006, 07:19 PM	#3
shopratles Senior Member Join Date: Dec 2005 Location: Texas Posts: 172	Wait though, not so fast. That TH400 has electronic kick-down that your truck isn't wired for. There is more work there than you know. Why are you having problems with 700R4's? What I mean is who is rebuilding these for you? With regular/decent service you should be getting at least 150,000 miles out of them. I would check around and get a good rebuilder to do the 700R4. Just my opinion though. Good luck.

02-28-2006, 07:25 PM	#7
mrjohnwayne Senior Moderator Join Date: Apr 2005 Location: Texas Posts: 3,722	They Yoke on the 400's bolts to the tailshaft of the transmissopn. You'll have to lengthen the first half of the shaft, along with reconfiguing the yoke situation. As far as the shifting goes I don't think you would want to run a daily driver with what I mentioned before. From the looks of it you already have a tranny that'll serve that purpose shift wise. hope this helps __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

03-01-2006, 03:52 PM	#8
mittan88 Junior Member Join Date: Feb 2006 Posts: 5	mr. john wayne i meant to ask if the spline is the same on the 700 as the 400 or will I have to change it the 400 is the same length as the 700 so the length thing will not be a big issue as far as a daily driver it won't be so I would really like to hear your shift thing. I want it to snape your head off when it shifts. thanks and hope to here from you,

03-01-2006, 04:57 PM	#9
mrjohnwayne Senior Moderator Join Date: Apr 2005 Location: Texas Posts: 3,722	With a decent shift kit, you can block off the detent solenoid (please don't hold me to this its been a long time, but any tranny shop that builds performance trannies can help) take the springs out of the 2nd gear govenor, and block off the 3rd gear govenor. To do so you remove the c-clip that holds the govenor in place. Do not remove the govenor. Add washers around the shaft until no movement occurs whild c-clip is in place. I can't remember if that is all. It's been a few years since I last rebuilt mine. As for the spline I'm pretty sure the 400 is bigger. As I said it's been along time since i've messed with any automatics. Hope this helps. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

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