700r4 4x4 conversion:spacer vs. output shaft

[JJ55chevy]

I want to go with a 700r4 in my 72 chevy 4x4. I have read that attaching it to a NP205 is easy to do but it can be done two ways, either with a spacer or replacing the output shaft. what are the pros and cons to each? also, what do I have to look out for as far as what year 700r4 to shop for and what controls the kick down? thanks for the help!!

[truckster]

I'll be following this thread, because I want to do the same with my Blazer. I've done a lot of reading on the board, and I'm fairly convinced the way to go is with an Advanced Adapters output shaft (especially since I plan on having the trans rebuilt, and that's a good time to install the shaft) and moving the engine forward to keep the T-case in the same place. But I'm still not 100% clear if that's the way to do it, and I'm looking forward to input from people who have actually done the swap on a 4X4.

[JJ55chevy]

Originally Posted by truckster

I'll be following this thread, because I want to do the same with my Blazer. I've done a lot of reading on the board, and I'm fairly convinced the way to go is with an Advanced Adapters output shaft (especially since I plan on having the trans rebuilt, and that's a good time to install the shaft) and moving the engine forward to keep the T-case in the same place. But I'm still not 100% clear if that's the way to do it, and I'm looking forward to input from people who have actually done the swap on a 4X4.

I was wondering about moving the engine forward, my last truck I built was a 69 GMC 2wd and I ordered my exhaust from JC Whitney for about $200 and it fit like a charm(they are made by heartthrob exhaust in Minnesota) I wonder if I will have the same kind of luck if I shift the engine forward.

[crashflow]

I too am interested in this. I just stuffed a big block in my 72 blazer and wanted to go with a 700r4 but my transmission guy told me buy the time I put the shaft in and built it to take the power of the big block that for the money I could buy extra gas for years from the loss of fuel economy from running a th350. after the install I noticed that had I moved the engine ahead then the front cross member also would need to move forward to clear the headers.. good luck and keep us posted how it goes for you.

[JJ55chevy]

Originally Posted by crashflow

I too am interested in this. I just stuffed a big block in my 72 blazer and wanted to go with a 700r4 but my transmission guy told me buy the time I put the shaft in and built it to take the power of the big block that for the money I could buy extra gas for years from the loss of fuel economy from running a th350. after the install I noticed that had I moved the engine ahead then the front cross member also would need to move forward to clear the headers.. good luck and keep us posted how it goes for you.

I am only guessing but with the big block wouldn't your best bet be a turbo 400 to get the most bang for the buck?

[crashflow]

Originally Posted by JJ55chevy

I am only guessing but with the big block wouldn't your best bet be a turbo 400 to get the most bang for the buck?

that's what I asked my transmission guy too. He said they only put a 400 behind the big block for a coulple years and they put the 350 behind it forever. I don't know but he said it will hold up so I am hoping.

[SS Tim]

Was doing some research into this last year. Basically an additional 2.5" between the block and the t-case is needed for the shortest conversion.


"No modifications to the case, it goes in just like the stock one. The only difference is that it’s shorter than the stock one.

Basically, the 700R4 is very similar to the TH350: they are both 27 spline and both use the same 4 bolt tailhousing pattern. The issue is that the 700R4 output shaft is ~2” longer than the TH350 output, so you can install a shorter output or a spacer (to make up for the 2”) and at that point the back of the 700R4 looks just like a TH350.

The shaft will work in any 700R4.

Using the new output shaft is the shortest way to do it, it uses the adapter and drive sleeve that are already in the truck. The 700R4 case is still ~2-1/2” longer than the TH350 case and there isn’t a way around that.


Chris Holick
Engineer, Research and Development
Offroad Design
484 County Road 113
Carbondale, CO 81623
970-945-7777
offroaddesign.com"



From:
Sent: Thursday, March 13, 2014 1:39 PM
To: ChrisH@offroaddesign.com
Subject: New Short Output Shaft for TH700R4, to Mimic TH350 Allowing Use of an NP203 or NP205

http://offroaddesign.com/catalog/trannyoutput.htm

Chris,
Have a couple of questions about the advantages of this shaft.
Understand it replaces the output shaft of the trans and requires a teardown to install.
"Installation requires pretty major surgery on the TH700..."
Are any case machining operations required?
Is it a stand alone modification that could be transferred to a new transmission on the road in the event of trans. failure?
Does it simply negate the need of a spacer and shaft trimming or is there more?
http://offroaddesign.com/catalog/700r4spacer.htm
Will using the shaft reduce the 700R4 length down to a drop in replacement for a TH350 without moving the engine forward or the t-case aft in a 71 Chevy K20? The intent is to maintain a stock as possible vehicle yet gain the fourth speed O/D.

Thanks,
Tim

[Maxxd07]

I converted my 80 with a 205 transfer case and I had to change the shaft and install an adapter. I got the parts from a local tranny shop. I told him what I was doing and he got me the parts and I did it myself. It was 10+ years ago and I think I paid about $130 for the shaft and adapter. The shaft used the same coupler from the turbo 350. An 87 and up 700 will be the better tranny since they used a bigger input shaft and the spine count went up.(27 to 30 I think) They have a tv cable that attaches to the carb that controls the shifting up and down. They NEED to be set correctly or damage will occur. They are not to bad to set but the best is to set them with a pressure gauge. I have a toggle switch in the cab to control the lockup for the torque converter. In my opinion 3.73 gears or lower the 700r4 works pretty good. I had one in front of 3.08s with 31 inch tires and I never dropped it into od unless I was on the interstate running 75+mph.

[57taskforce]

http://67-72chevytrucks.com/vboard/s...d.php?t=654021
Hate to say this but seems all the answers you seek were in this thread you started and opted out of about a month ago...

[JJ55chevy]

Originally Posted by 57taskforce

http://67-72chevytrucks.com/vboard/s...d.php?t=654021
Hate to say this but seems all the answers you seek were in this thread you started and opted out of about a month ago...

I opted out of that conversation because it turned into a "go LS or go home" build.....and if you read what was said, there never was a direct answer as to what would be the most practical route to take in putting a 700r4 transmission into a 72 Chevrolet truck. Not to mention all the crap I was getting for not going with a 4l60 or 4l80....my garage is not the land of plenty of time and money.

with that said, here I am asking "what is the most practical route for putting in an overdrive transmission into a 72 Chevrolet truck or should I just **** can that idea and buy a rebuilt turbo 350 and quit bugging the big guys with my little guy problems.

[72_K10_Vegas]

700R4 is the way I went. Moved the engine forward 1.875". Heard other guys moved as far forward as 2.25". There may be some clearance issue with front driveline and tranny pan depending on lift. Some guys I have read didn't have the clearance issue. As Tim noted above, Chris at ORD is very good resource.

[JJ55chevy]

Originally Posted by 72_K10_Vegas

700R4 is the way I went. Moved the engine forward 1.875". Heard other guys moved as far forward as 2.25". There may be some clearance issue with front driveline and tranny pan depending on lift. Some guys I have read didn't have the clearance issue. As Tim noted above, Chris at ORD is very good resource.

how did you connect the transmission to the transfer case? spacer?, different output shaft?

[68K30]

I used the Advanced adaptors shaft in mine. I put all the upgrades in the trans when I built it, it is bolted to a 454. the engine mounts are in the original frame holes and I did not modify either driveshaft. The only mod I did was drilling new transfer case cross member holes 5/8" back from the factory holes. My 72 frame originally had a 350, Turbo 350 and NP 205.
Hope this helps
Bill

[jjzepplin]

I did mine in 1999. It has a 203 doubler too. Had it in a Blazer but since put the combo in my SWB. Running 4.10's. It loves 36" tires but can't afford some right now. I built the 700r4 with B-M guts and extra clutches etc. It is great and I tow a big 20' trailer. SO I guess it is a pretty solid unit. 1989 trans.

[DeadheadNM]

Been there done that! See my K20 build linked in my signature below. Basically, move the engine forward (1.75" IIRC - see thread), use Advanced Adapters 700r4 to NP205 output shaft, and use the linkage from Bowtie Overdives - done. The fan is REALLY close to the shroud and the angles for the metal upper rad pipe are more acute but workable with slightly shorter hoses. You'll need to go with a 2wd throttle cable to but cinch up the slack. Good luck. Pete

[JJ55chevy]

Originally Posted by DeadheadNM

Been there done that! See my K20 build linked in my signature below. Basically, move the engine forward (1.75" IIRC - see thread), use Advanced Adapters 700r4 to NP205 output shaft, and use the linkage from Bowtie Overdives - done. The fan is REALLY close to the shroud and the angles for the metal upper rad pipe are more acute but workable with slightly shorter hoses. You'll need to go with a 2wd throttle cable to but cinch up the slack. Good luck. Pete

there we go, that's what I was looking for, details!!!! thank you!!

[DeadheadNM]

Originally Posted by JJ55chevy

there we go, that's what I was looking for, details!!!! thank you!!

You bet. I went with a BO level II K-case 700r4. The owner of BO is helpful and did the same conversion in his 72 K20. It runs low RPMs with the 4.10 Eaton rear.

Also, if you have an OEM tilt column repro lenses are available with an added "O" for overdrive that fit nicely into the original housing and look otherwise more-or-less original. Haven't really been able to dial in the neutral safety switch from the OEM column though - the truck will start in neutral but not in park.

[jjzepplin]

Originally Posted by DeadheadNM

You bet. I went with a BO level II K-case 700r4. The owner of BO is helpful and did the same conversion in his 72 K20. It runs low RPMs with the 4.10 Eaton rear.

Also, if you have an OEM tilt column repro lenses are available with an added "O" for overdrive that fit nicely into the original housing and look otherwise more-or-less original. Haven't really been able to dial in the neutral safety switch from the OEM column though - the truck will start in neutral but not in park.

I seem to recall grinding something on my original column and that's how I got the trans to go into 1st gear. The neutral switch never got adjusted and worked as it did before. The gear indicator just goes off the map a bit. I don't have a tilt though.

[57taskforce]

JJ. Take a deep breath man I wasn't trying to start an altercation. My apologies. I'll admit I skimmed thru your initial post rather than fully reading it. After reading it I do see it's a different question. With that being said relax a little bit buddy, these forums are to learn and enjoy our old trucks not being at each other's throats. I'm certainly not a "big guy" at all and I'd venture to say your not bugging anybody. If you think this forum is bad read around on one like pirate4x4. People here are mostly mild mannered and interested in sincerely helping one another. If I've ever come across other than that my apologies.

As for your 700r: I would highly suggest you use these two things for torque converter control and your detent cable.
Your gonna have to select the carb you are running from this page and it will take you to everything you need to correctly put a tv cable in your trans.
http://www.bowtieoverdrives.com/cata...BCAT&CATID=WA3

Also: this lockup kit is pretty decent:
http://www.bowtieoverdrives.com/cata...php?ITEMID=332
Keep in mind with the detent cable if the geometry at the carb is not 100% correct the trans won't last long. That is why the above kit is a good buy. It will give you the right geometry for the carb you run.
Lastly good luck and please keep us posted on your progress!
Tyler

[JJ55chevy]

the more I read up on this 700r4 or any other type of overdrive conversion I am leaning more towards just going with a turbo 350 and moving on with my project.... not that everyone talked me out of it but in reality I am more informed now of all the hidden extras that go along with just bolting in a transmission...this truck will not see more than a couple thousand miles a year so it is really not worth all the trouble just to gain an overdrive...next step will be to get the 350 rebuilt and I can start putting things together (the engine was delivered last week)....thanks for the input everyone!!!!