Tranny swap ?, I searched ... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cochino12 · 10-07-2008, 09:22 PM

Sorry for the dumb question, I searched but apparently I am search function slow ha ha.

I would like to swap the th350 for a 700r in my 86 lwb k20 w/np208 t-case. Other than the tranny itself what else is needed?

Thanks

**old Rusty C10** · 10-07-2008, 09:26 PM

for sure youll need the different indicator thing on the dash

cochino12 · 10-07-2008, 09:28 PM

Quote:

Originally Posted by old Rusty C10

for sure youll need the different indicator thing on the dash

ha ha, thats the only thing I was sure about.

Albatrossian · 10-07-2008, 09:33 PM

You might have to relocate the crossmember and/or get a different one since it's 4x4.. not sure though. The crossmember had to be moved when my truck was swapped from a 350 to a 700.

Jonboy · 10-08-2008, 08:08 AM

I am pretty sure it is a bolt in affair. Since your truck is an 86, all of the necessary holes should be in the frame if the crossmember does need to be moved. The Th350 thould have a TCC also, so that will plug in. The bracket for the kickdown cable is the same to hold the 700's TV cable. I don't remember the output shafts having different splines, but it has been over 10 years since I have had a 4WD. If you found a 700/208 combo for sale, it would bolt right in for sure.

abebummy26 · 10-08-2008, 09:38 AM

Are you going to use your old Tcase?

JonnyTechMech · 10-09-2008, 11:34 AM

I haven't done such a swap, but don't you have to get a shorten drive shaft? It was my impression that the 700R4 was longer than a th350 or th400.

cochino12 · 10-09-2008, 08:33 PM

Quote:

Originally Posted by abebummy26

Are you going to use your old Tcase?

That was the plan

Quote:

Originally Posted by JonnyTechMech

I haven't done such a swap, but don't you have to get a shorten drive shaft? It was my impression that the 700R4 was longer than a th350 or th400.

Thats what I thought, I dont have a 700 here to measure though. I figured more people here would have done this swap?

Albatrossian · 10-09-2008, 08:37 PM

Between a TH350 with a 9-1/4" tail and a 700 there is only a 1/8 difference.

cochino12 · 10-09-2008, 09:33 PM

Quote:

Originally Posted by Albatrossian

Between a TH350 with a 9-1/4" tail and a 700 there is only a 1/8 difference.

hmm so just a crossmember swap? sounds pretty simple guess I could get to the junk yard and do a little research too.

Thanks everyone

Jonboy · 10-10-2008, 09:16 AM

Quote:

Originally Posted by Albatrossian

Between a TH350 with a 9-1/4" tail and a 700 there is only a 1/8 difference.

The 4wd doesn't use the tailshaft housing. The flange that bolts to the extension housing bolts to the transfer case adapter, then the transfer case.

I was curious about the transfer case as I figured it might be easier to find a 700/208 combo pretty reasonable, and then you would know the splines would be the same.

abebummy26 · 10-10-2008, 01:45 PM

The input shaft splines might be different on the Tcase. I'm not sure though.

10-07-2008, 09:22 PM	#1
cochino12 It followed me home? Join Date: Mar 2003 Location: Yup Posts: 5,751	Tranny swap ?, I searched ... Sorry for the dumb question, I searched but apparently I am search function slow ha ha. I would like to swap the th350 for a 700r in my 86 lwb k20 w/np208 t-case. Other than the tranny itself what else is needed? Thanks __________________ Adam That's why they call it a shortcut Kyle, if it was easy it would just be the way. 86 c-10 SWB 85 CCSB 90 GMC K30 Crew SRW 1985 C30 Dually

10-07-2008, 09:26 PM	#2
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	Re: Tranny swap ?, I searched ... for sure youll need the different indicator thing on the dash __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

10-07-2008, 09:33 PM	#4
Albatrossian Georgia Boy Join Date: Jun 2008 Location: Douglas, Georgia Posts: 370	Re: Tranny swap ?, I searched ... You might have to relocate the crossmember and/or get a different one since it's 4x4.. not sure though. The crossmember had to be moved when my truck was swapped from a 350 to a 700.

10-08-2008, 08:08 AM	#5
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	Re: Tranny swap ?, I searched ... I am pretty sure it is a bolt in affair. Since your truck is an 86, all of the necessary holes should be in the frame if the crossmember does need to be moved. The Th350 thould have a TCC also, so that will plug in. The bracket for the kickdown cable is the same to hold the 700's TV cable. I don't remember the output shafts having different splines, but it has been over 10 years since I have had a 4WD. If you found a 700/208 combo for sale, it would bolt right in for sure.

10-08-2008, 09:38 AM	#6
abebummy26 Registered User Join Date: Sep 2006 Location: New Haven, MO Posts: 1,243	Re: Tranny swap ?, I searched ... Are you going to use your old Tcase? __________________ -Lincoln 1987 GMC S15 (soon to be a chevy clone) 2.5l, 4 speed, no ps, no pb, no ac Silence is golden, but duct tape is silver. Spoken by Cletus the hillbilly I like stickers... a whole bunch.

10-09-2008, 11:34 AM	#7
JonnyTechMech STOP! Hamma time!!! Join Date: Feb 2005 Location: Dallas TX. Posts: 145	Re: Tranny swap ?, I searched ... I haven't done such a swap, but don't you have to get a shorten drive shaft? It was my impression that the 700R4 was longer than a th350 or th400. __________________ Plan your work and work your plan!!!, or pitty da fool!! 87 GMC BaseTrim, 305 under the wrench/TH400/ 92 Chevy 1500, 350,TH700R4 sittin on dubs

10-09-2008, 08:37 PM	#9
Albatrossian Georgia Boy Join Date: Jun 2008 Location: Douglas, Georgia Posts: 370	Re: Tranny swap ?, I searched ... Between a TH350 with a 9-1/4" tail and a 700 there is only a 1/8 difference.

10-10-2008, 01:45 PM	#12
abebummy26 Registered User Join Date: Sep 2006 Location: New Haven, MO Posts: 1,243	Re: Tranny swap ?, I searched ... The input shaft splines might be different on the Tcase. I'm not sure though. __________________ -Lincoln 1987 GMC S15 (soon to be a chevy clone) 2.5l, 4 speed, no ps, no pb, no ac Silence is golden, but duct tape is silver. Spoken by Cletus the hillbilly I like stickers... a whole bunch. Last edited by abebummy26; 10-10-2008 at 01:46 PM.

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