1976 Highboy, c6 with 7" tailhousing, divorced np205

intro: Bought a GearVendors o/d a while ago and finally picked it up last night. I spoke with them on the phone and since I'd like the option of using it on something else if I decide to, it was suggested that I get the short version to go in between the trans and transfer case on my '76 HiBoy.
[it'll be: engine-->C6-->GV-->NP205] At the time of purchase I asked if there was anything "special" that I'd need to have done to put it on and was told that basic hand tools were all that were required other than having a new driveline built.

Long story short, the directions instruct you to have a trans shop replace the C6 output shaft with the supplied gearvendors output shaft. After reading this, I called them and at first the guy told me this was correct, that I would need to take it to a shop and essentially have it torn down and shafts swapped... I said "alright I'm going to need you to send me the NP205 stuff because I'm not tearing the trans down that's ridiculous, if not I'll just return it"

as soon as the word "return" was uttered, he quickly asked to research it a little and call back. Twenty minutes later he called back and told me that the short c6's that were put in the highboys were different than others; they only need the tailhousing removed and once it's gone, the output shaft could be removed simply by taking a retaining clip out and sliding the shaft out. "all others have to be torn down, but not the one that's in your truck"

I have a hard time believing that the internals are somehow different on this trans simply because of the tailhousing, but figured I'd get a reliable answer from the wealth of knowledge on this forum.

so, can the output shaft in the shorter C6's used in Highboys be removed by taking the tailhousing off and taking out one clip without tearing down the trans? Or is GearVendors trying to feed me a line of ****?

 

bump......

 

Call Brian's truck shop, BTS transmissions. He will know.

 

Will do, thank you.

 

The hiboy C6 has a fixed yoke (bolts on). this is why the output needs changed, the threaded end of the output shaft will not allow the GV to mate up.

I think for most applications, gearvendors supplies a spud shaft coupler to mate their OD unit to the existing trans output shaft. With a fixed yoke this isn't possible.

 

yep yep. they're selective with those little details, like leaving out the part about the trans needing to be torn down.

The guy I spoke to was basically trying to argue with me when I said they'd NEVER said anything about this shaft needing to be installed, and last time I called I ended up writing the owner of the company asking him why his employee was giving contradicting and incorrect information.

Not very pleased with them at all, I'll just call and request the NP205 adapter since I've had it with "dave". For north of $3k I expected a lot better.

 

Have you considered how short, the already short rear d-shaft will be after you mount the GV on the 205?
I think a CV joint would be mandatory to keep driveline angles correct.

I have no idea how hard it is to swap the hiboy C6 output shaft but thats what I'd do. Also with the GV behind the C6 you still have the ability of 4x4+O/D.

 

That's why I opted for the c6 variety so I wouldn't ever have to worry about o/d kicking in while I'm in 4x4, just install it and forget about it. also it'll fit on anything I get whereas the long one might not fit on a rig in the future.
That's where "dave" contradicted the owner... I spoke with the owner about the 8" driveline and my concerns about extreme universal joint angles; he said that it'd been done plenty of times and he's yet to hear any complaints. I called one last time for something and got "dave" on the phone, dave essentially said that was an idiotic idea and had no idea who would ever sell me the short c6 kit since it was such a terrible place to put the o/d [which prompted me to write the owner and ask what the hell his employee was talking about].

I've got a big move in 12 days, I'll just say hell with it and get the 205 adapter and be done with them.... hopefully.

 

I hope this is not too late. I have a 75 highboy that I swapped a 360 to a 460 in. I swapped the 460 & 2wd trans out of a 76 E350 van. The bell housings & tailshafts were different. I had to swap the highboy 4x4 yoke tailshaft to the 2wd slip yoke tranny.

The 2wd tranny with the slip yoke I had to completely disassemble, because there was a retainer clip on the front of the tailshaft. It was only accessible by tearing into the middle of the tranny.

I believe on the 4wd with the fixed yoke there was no retainer clip on the front of the tailshaft. There's a clip on the rear of the tailshaft by the bearing. I think all that holds it together is the yoke tightens up againt the bearing & the clip on the forward side of the tailshaft bearing holds it in place. Then the tailshaft housing bolts to the trans to keep it in place.

I think all you have to do is leave the yoke on & just remove the bolts that hold the tailshaft housing to the trans. The whole assembly (tailshaft housing, tailshaft, & yoke) should just pull out as a unit.

It's been over 3 years since I did this, so I'm not 100% sure. I do know for sure my highboy tailshaft had no retainer clip on the front of the tailshaft. When I installed the tailshaft I do know for sure I intalled it as a unit, (tailshaft housing, tailshaft, & yoke).

Hope this helps

 

I almost forgot. You're highboy tailshaft has the holes for mounting the transfer case linkages. I don't think the gear vendors does so you'll have to work out your transfer case linkage mounting somehow.

 

75 Highboy c6 tailshaft & housing assembly


Here's a pic of a 75 highboy c6 tailshaft & housing as a unit.