Another 700r4 conversion question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

TN4X4 · 10-23-2006, 11:00 PM

I'm still somewhat of a newby here so please forgive the repeat of this question. I drive about 50 miles (interstate) one way to work. My truck has a 4.11 rearend and 33" tires. Obiviously, this combo and a TH350 doesn't do well. I've researched these forums for quite some time and I haven't found anyone that has layed out in simple terms how to converted a '67-'72 K20 from a TH350 to a 700R4. I'm sure I've overlooked it. I'm pretty familiar with the 700, but not with these trucks, especially the 4wd's. For instance, I'm not sure what kind of transfer case I've got (np205?)and how/if the 700 would bolt to it (shaft size and spline count differences). Any advice and direction would be a huge help (FAQ maybe). I'm aware that the 700 is longer so I'll have the move the motor forward or the tranny mount back (which is what I'll be doing) and shorten the drive shaft. It can't be that simple, right? Thanks.

earl87gta · 10-24-2006, 04:03 AM

Hey I go threw your neck of the wood all the time my wife is from murfreesburo here you go this should help. http://67-72chevytrucks.com/vboard/s...d.php?t=128495

TN4X4 · 10-26-2006, 11:13 PM

Thanks for the lead. Aparently all I need is the adapter, saw off 15/16" of the 700r4's output shaft, move the the trans mount a few inches, cut the driveshaft down and dial in the TV cable. Sound about right? Definitely not a beginner's project.

earl87gta · 10-27-2006, 01:29 AM

with the adaptor no cuting needed its all bolt in. its not that hard and as long a you can turn a wrench you will be ok. Dialing ing the TV cable will be the hard part and its not that bad. you will also need to change out you break switch and use one from a new truck to unlock the TC or by one of the expencive kits. I recomend going hear http://www.tvmadeez.com/article/index.php good artical on the tv cable. they also sell kits for the TC lockup for like $75.

earl87gta · 10-27-2006, 01:31 AM

I will be puting one in the burb soon but Im going to use a devorced transfer case so it wont help with the adaptor part. wish I still had pics of the blazer I had with the 700r4 for you.

TN4X4 · 10-27-2006, 05:59 PM

Thanks again. Yeah, it sure would be nice to see what these steps should look like. I just rebuilt my motor and I'd like not to wear it out in 10k miles. One of these r4's would do wonders.

benoit454 · 10-29-2006, 08:48 PM

I'm doing the opposite sometime soon hopefully.

I got an 86 k10 with 700 which sucks and changing it out to th350.

earl87gta · 10-30-2006, 01:18 AM

Quote:

Originally Posted by benoit454

I'm doing the opposite sometime soon hopefully.

I got an 86 k10 with 700 which sucks and changing it out to th350.

I would think if your taring up 700r4 your going to eat up a th350 just as easy. I may be wrong here but a 700r4 is not much difrent then a th350 other then the lock up converter to give it an over drive. you may want to go to a th400. I have never had a trouble with the 700r4s and my TA dynoed at 430 lb of T and Ive never had trouble with it Ive broke a few axles but no trans trouble yet I did replace the sun gear in it with an after market one before it went in to the car that is the part that is supose to break all the time and it has a TCI shift kit.

**Chevy Fleetside** · 11-03-2006, 10:32 AM

The 86 year model was a weaker tranny anyway.. You want a year model 88-92 if you are doing a swap.. I put a 700R4 and NP208 from an 88 Suburban Donor in my 79. I pretty much bolted in. I had to drill two holes for the crossmember and that was it for that. I had to get a new driveshaft because my old one had a slip joint in it and I needed a solid one. The 203 transfer case I had in there was a full time 4x4 and it had to go. Man that thing was heavy.. I wired up a manual switch to lock up the torque converter that I turn on and off when I want it. If I forget to turn it off it lets me know as soon as it shifts into 2nd gear.. The tranny was rebuilt with the comercial clutch pack and also a Reprogramming shift kit. I am not crazy about the 1 2 shift but the rest feel great.. Gas milage went from about 10 for city and freeway up to about 15 or better.. I never really did this clearly. I will say I have recorded 17mpg out of it but I know this is not constant. I am running 3.73 gears..

TN4X4 · 11-13-2006, 12:09 AM

I guess I have a slip yoke. Would I have to change out my drive shaft? I thought I could just shorten it?

10-23-2006, 11:00 PM	#1
TN4X4 Registered User Join Date: Jul 2006 Location: Lebanon, TN Posts: 23	Another 700r4 conversion question I'm still somewhat of a newby here so please forgive the repeat of this question. I drive about 50 miles (interstate) one way to work. My truck has a 4.11 rearend and 33" tires. Obiviously, this combo and a TH350 doesn't do well. I've researched these forums for quite some time and I haven't found anyone that has layed out in simple terms how to converted a '67-'72 K20 from a TH350 to a 700R4. I'm sure I've overlooked it. I'm pretty familiar with the 700, but not with these trucks, especially the 4wd's. For instance, I'm not sure what kind of transfer case I've got (np205?)and how/if the 700 would bolt to it (shaft size and spline count differences). Any advice and direction would be a huge help (FAQ maybe). I'm aware that the 700 is longer so I'll have the move the motor forward or the tranny mount back (which is what I'll be doing) and shorten the drive shaft. It can't be that simple, right? Thanks. __________________ '72 LWB K20 - SOLD '66 Mustang 289 3spd '42 Chevrolet Fire Truck

10-24-2006, 04:03 AM	#2
earl87gta Senior Member Join Date: Dec 2003 Location: Kingsport TN Posts: 4,641	Re: Another 700r4 conversion question Hey I go threw your neck of the wood all the time my wife is from murfreesburo here you go this should help. http://67-72chevytrucks.com/vboard/s...d.php?t=128495 __________________ Earl 68 2500 4x4 GMC Burb Last edited by earl87gta; 10-24-2006 at 04:06 AM.

10-26-2006, 11:13 PM	#3
TN4X4 Registered User Join Date: Jul 2006 Location: Lebanon, TN Posts: 23	Re: Another 700r4 conversion question Thanks for the lead. Aparently all I need is the adapter, saw off 15/16" of the 700r4's output shaft, move the the trans mount a few inches, cut the driveshaft down and dial in the TV cable. Sound about right? Definitely not a beginner's project. __________________ '72 LWB K20 - SOLD '66 Mustang 289 3spd '42 Chevrolet Fire Truck

10-27-2006, 01:29 AM	#4
earl87gta Senior Member Join Date: Dec 2003 Location: Kingsport TN Posts: 4,641	Re: Another 700r4 conversion question with the adaptor no cuting needed its all bolt in. its not that hard and as long a you can turn a wrench you will be ok. Dialing ing the TV cable will be the hard part and its not that bad. you will also need to change out you break switch and use one from a new truck to unlock the TC or by one of the expencive kits. I recomend going hear http://www.tvmadeez.com/article/index.php good artical on the tv cable. they also sell kits for the TC lockup for like $75. __________________ Earl 68 2500 4x4 GMC Burb Last edited by earl87gta; 10-27-2006 at 01:30 AM.

10-27-2006, 01:31 AM	#5
earl87gta Senior Member Join Date: Dec 2003 Location: Kingsport TN Posts: 4,641	Re: Another 700r4 conversion question I will be puting one in the burb soon but Im going to use a devorced transfer case so it wont help with the adaptor part. wish I still had pics of the blazer I had with the 700r4 for you. __________________ Earl 68 2500 4x4 GMC Burb

10-27-2006, 05:59 PM	#6
TN4X4 Registered User Join Date: Jul 2006 Location: Lebanon, TN Posts: 23	Re: Another 700r4 conversion question Thanks again. Yeah, it sure would be nice to see what these steps should look like. I just rebuilt my motor and I'd like not to wear it out in 10k miles. One of these r4's would do wonders. __________________ '72 LWB K20 - SOLD '66 Mustang 289 3spd '42 Chevrolet Fire Truck

10-29-2006, 08:48 PM	#7
benoit454 Chris Join Date: Nov 2004 Location: Monaville, WV Posts: 3,737	Re: Another 700r4 conversion question I'm doing the opposite sometime soon hopefully. I got an 86 k10 with 700 which sucks and changing it out to th350. __________________ Chris GIT R DONE!!!!!! Check out all our rides, http://www.cardomain.com/id/benwa454

11-03-2006, 10:32 AM	#9
Chevy Fleetside Registered User Join Date: Sep 2006 Location: San Francisco Posts: 4,782	Re: Another 700r4 conversion question The 86 year model was a weaker tranny anyway.. You want a year model 88-92 if you are doing a swap.. I put a 700R4 and NP208 from an 88 Suburban Donor in my 79. I pretty much bolted in. I had to drill two holes for the crossmember and that was it for that. I had to get a new driveshaft because my old one had a slip joint in it and I needed a solid one. The 203 transfer case I had in there was a full time 4x4 and it had to go. Man that thing was heavy.. I wired up a manual switch to lock up the torque converter that I turn on and off when I want it. If I forget to turn it off it lets me know as soon as it shifts into 2nd gear.. The tranny was rebuilt with the comercial clutch pack and also a Reprogramming shift kit. I am not crazy about the 1 2 shift but the rest feel great.. Gas milage went from about 10 for city and freeway up to about 15 or better.. I never really did this clearly. I will say I have recorded 17mpg out of it but I know this is not constant. I am running 3.73 gears..

11-13-2006, 12:09 AM	#10
TN4X4 Registered User Join Date: Jul 2006 Location: Lebanon, TN Posts: 23	Re: Another 700r4 conversion question I guess I have a slip yoke. Would I have to change out my drive shaft? I thought I could just shorten it? __________________ '72 LWB K20 - SOLD '66 Mustang 289 3spd '42 Chevrolet Fire Truck



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