th400 to 700r4 swap question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

scsindust · 05-03-2009, 07:02 PM

ok,

My 89 Burb has a th400 in it right now, with the 350 engine. I just picked up a 700r4 from what I think was a 86 blazer. It came with the transfer case also. Anyway, this is a direct bolt in right? I know I need to move the crossmember back a set of holes, and I was told the 400 is just about the same length as th e700, so the driveshaft can be reused. My biggest question is the tc lockup. Do I need extra wiring for the tc? Thanks!

tvblazer78 · 05-03-2009, 08:07 PM

You will need to add a lock up for the 700, B&M and TCI makes a good kit that will let you lock it up after you doing 55 or 60. That is about the only time you need it to lock up is when you are going over 55 for any long times.

And you need to look at the the splines counts are on both 700 and 400 you will need them to be the same.. Good luck..

scsindust · 05-03-2009, 08:16 PM

You mean the splines where it mounts to the xfer case? I am just going to use the one that I got with the trans. I take it that the trans already has the solenoid in it to lock up the trans, and I just need the computer to tell it when to lockup, right? I appreciate the help!

scsindust · 05-03-2009, 08:32 PM

Actually, is the wiring in place on my truck? Can I get an ECU for an 89 with a locking 700? Instead of keep bothering you all, is there a good site that explains all this. I guess my confusion starts with does an 89 come with a 700 w/ a locking tc? It just seems that it should be a direct swap in....

JESSEGALLEGOS · 05-19-2009, 11:00 PM

Quote:

Originally Posted by scsindust

ok,

My 89 Burb has a th400 in it right now, with the 350 engine. I just picked up a 700r4 from what I think was a 86 blazer. It came with the transfer case also. Anyway, this is a direct bolt in right? I know I need to move the crossmember back a set of holes, and I was told the 400 is just about the same length as th e700, so the driveshaft can be reused. My biggest question is the tc lockup. Do I need extra wiring for the tc? Thanks!

I have a 2WD 1982 K5 blazer which had a 1991 700R4 and just reaplced it with a TH400. I will be willing to swap you transmission crossmembers because you'res will not work. I also have the kick down cable and any wiring if needed.

scsindust · 05-20-2009, 07:30 PM

I've been told that I have to move the cross member back a set of holes and it will all fit right. Mine is a 4x4, which might be the difference between it working and not?

Albatrossian · 05-20-2009, 09:09 PM

I do know that a TH400 and a 700R4 in 2WDs are *not* the same length. It's very possible they don't use the same length driveshaft. A 9" tailshaft TH350 and 700 are 1/8" difference in length.

05-03-2009, 07:02 PM	#1
scsindust Registered User Join Date: May 2009 Location: Jessup, MD Posts: 57	th400 to 700r4 swap question ok, My 89 Burb has a th400 in it right now, with the 350 engine. I just picked up a 700r4 from what I think was a 86 blazer. It came with the transfer case also. Anyway, this is a direct bolt in right? I know I need to move the crossmember back a set of holes, and I was told the 400 is just about the same length as th e700, so the driveshaft can be reused. My biggest question is the tc lockup. Do I need extra wiring for the tc? Thanks! __________________ Jamie Play truck / kid hauler - 1989 V2500 Burb 4x4, 350, 700R4, 4" lift, headers, elec fans, the normal mods. Getting ready for the LS1 swap!! Last edited by scsindust; 05-03-2009 at 07:03 PM. Reason: additional info

05-03-2009, 08:07 PM	#2
tvblazer78 Low & Fast! Join Date: Jan 2007 Location: Knoxville, TN Posts: 3,110	Re: th400 to 700r4 swap question You will need to add a lock up for the 700, B&M and TCI makes a good kit that will let you lock it up after you doing 55 or 60. That is about the only time you need it to lock up is when you are going over 55 for any long times. And you need to look at the the splines counts are on both 700 and 400 you will need them to be the same.. Good luck.. __________________ Southeastern Mini Truckin' Nationals April 27 and 28, 2012

05-03-2009, 08:16 PM	#3
scsindust Registered User Join Date: May 2009 Location: Jessup, MD Posts: 57	Re: th400 to 700r4 swap question You mean the splines where it mounts to the xfer case? I am just going to use the one that I got with the trans. I take it that the trans already has the solenoid in it to lock up the trans, and I just need the computer to tell it when to lockup, right? I appreciate the help! __________________ Jamie Play truck / kid hauler - 1989 V2500 Burb 4x4, 350, 700R4, 4" lift, headers, elec fans, the normal mods. Getting ready for the LS1 swap!!

05-03-2009, 08:32 PM	#4
scsindust Registered User Join Date: May 2009 Location: Jessup, MD Posts: 57	Re: th400 to 700r4 swap question Actually, is the wiring in place on my truck? Can I get an ECU for an 89 with a locking 700? Instead of keep bothering you all, is there a good site that explains all this. I guess my confusion starts with does an 89 come with a 700 w/ a locking tc? It just seems that it should be a direct swap in.... __________________ Jamie Play truck / kid hauler - 1989 V2500 Burb 4x4, 350, 700R4, 4" lift, headers, elec fans, the normal mods. Getting ready for the LS1 swap!! Last edited by scsindust; 05-03-2009 at 08:35 PM.

05-20-2009, 07:30 PM	#6
scsindust Registered User Join Date: May 2009 Location: Jessup, MD Posts: 57	Re: th400 to 700r4 swap question I've been told that I have to move the cross member back a set of holes and it will all fit right. Mine is a 4x4, which might be the difference between it working and not? __________________ Jamie Play truck / kid hauler - 1989 V2500 Burb 4x4, 350, 700R4, 4" lift, headers, elec fans, the normal mods. Getting ready for the LS1 swap!!

05-20-2009, 09:09 PM	#7
Albatrossian Georgia Boy Join Date: Jun 2008 Location: Douglas, Georgia Posts: 370	Re: th400 to 700r4 swap question I do know that a TH400 and a 700R4 in 2WDs are not the same length. It's very possible they don't use the same length driveshaft. A 9" tailshaft TH350 and 700 are 1/8" difference in length. __________________ 81 GMC High Sierra, 2WD, 357ci/700R4, 3.73s, posi.



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