72 4x4 converting to 700R4 problem

[FrankHoy]

I have a question on converting a '72 4x4 to a 700R4.

I also posted this under the engine & driveline but thought that I might have better luck getting a response from someone with this conversion on this board.

I have read numerous threads on this conversion here and don't recall this ever being an issue or problem. Search sure would be nice right now

I have been doing a frame off and conversion and just put the motor and tranny into the finished frame. I am now having problems with the fit of the front driveshaft.

I am working with a 402 BB & NP205, adding in the 700R4 . Frame originally had a 350SB / 350Turbo / NP205. I am taking a 2WD BB cab & 402 and putting on the 4x4 frame with original NP205. Transmission/Tcase crossmember is in original position, with engine crossmember moved slightly ahead.

One variation I did make was change to a deep tranny pan.

The driveshaft has a regular u-joint with slip joint on end that is suppose to bolt to the front axle. It also has a constant velocity joint on the rear(I believe that's what they are called-"knuckle joint with two encased u-joints".) Attaching a picture of similar shaft.


Now the rear joint will not clear the corner of the tranny pan by the transfer case front output shaft. It does not appear that it would clear even with the original shallow pan.

Has anyone else had this problem? Can the drive shaft be flipped and have the knuckle joint on the front or must it be on the rear? Can the knuckle be converted to a regular u-joint? Other possibilites?

All help & suggestions greatly appreciated.

[Mudder]

There have been guys that have talked about this in length here.

[special-K]

A couple questions:1)Is the truck at original height?2)What method of adapting did you use?Did you use an adaptor-spacer,or AdvancedAdapters shaft-swap kit?

[FrankHoy]

Yes original stock height & I used an Advance Adapter output shaft.

[71RestoRod]

My front driveshaft / double cardon / CV joint clears the stock transmission pan on the 700R4… but not by much. I used the AA shaft also. No way could I fit a deep pan without some tricky modifications. I also have the cross member in the stock location with the engine moved forward. My Blazer is lifted slightly, but I would think you should clear the shallow pan at the stock height. I looked into altering a deep aluminum pan but ultimately opted for a stock shallow pan w/ a beefy aux. cooler.

You need to run the CV on the transfer case side. You can convert it to a single u-joint but the drive angles will be extreme... and won’t match between the front axle and t-case, so you’ll be asking for vibrations and other problems down the road.

[ckhd]

Do you have a digital camera? Take some pics of the problem area.

I wonder if it's the original style output of the t-case.

I'll try to get a pic of mine and post tomorrow. I left the camera at the house...

[super72bb]

This is an excellent question... I just have purchased the shaft kit and adapter from Advance Adapters to convert my 4speed/NP205 combo to a 700R4/Np205. As I was reading through the paperwork I saw a short message ***There may be some clearance problems around the front driveshaft output quill when doing this conversion***

So does this mean that we have to run with a factory pan on the 700R4 when we do the conversion or is there more to it than that???

[FrankHoy]

Sorry I have been slow to respond, been away for a few days. Thanks for the responses.

I guess I will try changing the pan back to original and checking clearance, this weekend. I'll let you know how it goes and if problems post some pics.

[super72bb]

Hey Frank

Just curious... how did you make out with changing the pan? Please let us know.

Curt

[FrankHoy]

Curt,

I actually just finished making the pan change last night. It does clear with the original pan. There is not much clearance though, probably 1/4"-1/2".

I am afraid hitting some big crater in the road or large bump, that would cause major flex in the front springs, might allow enough upward movement of the rear knuckle to hit the corner edge of the pan. I won't be doing much, if any, major off road mudding/hill/rock climbing but if was intending on it I think I would need to find a better solution.

I plan on leaving as is and watching it closely after getting on road. I am just completing the frame and drivetrain and starting on body work/paint. So it will be at least several months before I am able to do a good road test.

I think the only other option might be a spacer adapter, to push the whole trans & engine ahead an 1" or so. That would allow plenty of clearance. I am not sure if they make those for the 205 or not. Seems, I remember some talk about them here but that may have been for another setup.

Frank

[72longbed]

Frank,
there is an adapter that goes between the NP205 adapter and the 700R4 tailshaft case. You need to using a TH350 NP205 to use it though. I think its about 1 3/4" thick and would push everything forward enough to give some excellent firewall clearance for the Distr. also.

Not sure who is making/supplying these adapters, but its been on the 4x4 Board in the past.

72longbed

[K5KRAZIE]

A little late to the party, but oh well. I used the A/A shaft as it was the only option when I did my conversion. If I had the option I think I would have still used the shaft as I'm worried about length. If you use the shaft you have to use the 1/2 ton cv and a "factory" style pan. I have to tell you though I wheel the PEE out of my K5 and have yet to have a problem with that area of the drivetrain. I have broken the A/A shaft however. With the spacer option you have enough space to use a deep pan or the bigger (1350) cv, as the pan is now clear of the joint and the shaft size is the only limiting factor.

[72longbed]

Who knows where to get the 'spacers'??

72longbed

[FrankHoy]

I believe what you need is on this page: http://eshop.advanceadapters.com/com...=1123728704640

I know when I bought my adapter shaft, Advance Adapters is the only company I found that made them. They sell direct to anyone. Definitely not cheap though.

It looks like they have a few options, but some of the descriptions aren't real clear. Once you have a look at the web page, I would call and talk to someone, telling them what you have and what you want to do.

[72longbed]

They don't make these 'spacers', but thanks anyway.

[Russell]

Can you clock your transfercase a bit clockwise to drop the front output shaft down an inch or so? May require that you have a custom spacer made, but it would solve this issue, allowing you to run a deep pan for extra cooling, and still have plenty of driveshaft clearance. The 4x4 guys often do this, but in the opposite direction to reduce the possiblity of getting hung up on their case or something, but if you don't plan on wheeling the truck too often, it wouldn't be a big problem as far as I can tell.

The 205 is a straight through type case, meaning the front input and rear output would still be in line, it'd just adjust where the front output is