Slip Yoke vs. Fixed Yoke?

[FloridaPhil]

My past experience has been with cars, not trucks. The C6 I purchased to swap into my 68 F100 looks like it has a fixed yoke (universal joint connection bolted to the output shaft). My three speed manual had a traditional slip yoke. I read through this forum and it says something about a special fixed yoke driveshaft. I'm assuming I'll have to buy a new driveshaft for my manual to auto tranny swap. Can someone please explain how this works and what I need? Can a drive shaft shop supply this?

[PhantomoftheBumpside]

You are going to want a slip somewhere... the rear end moving causes the distance between the rear and trans to change. With a solid shaft between u-joints with no slip on the output, you're gonna break stuff. Probably on the first pot hole you try to ease through.

Sounds like your trans came from a LWB ... these trucks had two piece drive lines with a carrier bearing, so the slip is in the back half behind the carrier... but I think there was a SWB setup that still have a fixed yoke up front and a slip in the shaft...

[Kurt Combs]

I just had the opposite situation, slip joint and needed the fixed for my truck. Go to your local transmission shop and see if they have a tail housing off of a transmission with the slip yoke and what they want to swap the tail housings. Should be around two hours shop time and parts. While they are in the transmission they can change the front and rear seals which is a good thing.

[FloridaPhil]

I'm a little confused...(normal for me). Are you saying there are two types of truck C6 output shafts and matching tail housings; traditional slip yoke and fixed yoke? I assume all passenger cars used the long style tail housing and the traditional slip yoke? Did 1968 F100 2WD trucks have the fixed or slip yoke or both? I would rather not get into a two piece driveshaft. Can I buy the parts to change my short tail housing truck C6 to a slip yoke? If I can do this, will my 3 speed manual drive shaft work without modifications?

[FloridaPhil]

I spoke to a local tranny guy and he straighted me out on this. This is my first truck project and I had never heard of a slip joint drive shaft. I figured it had to slip somewhere or we would be in for a rough ride. He also told me the truck C6 I have is a heavy duty unit and the one to have. Whew, time for a nap...

[PhantomoftheBumpside]

The Hummer drive line is kind of set up like our old LWB Fords... except the 'male' front piece of the slip shaft is a tiny bit 'undersized' and has a pink teflon/miracle plastic coating on it to "keep it quiet".. if you pull it out and any rips off of it because it snags (and it is most likely going to gonna get snagged because it's gonna be chewed up)... well you gotta order a new drive line... or hope you get lucky with finding an undamaged set at the DRMO.

[Kurt Combs]

What did you decide to do for a drive shaft? Two piece with center support? I'm just curious.

[FloridaPhil]

I'm not sure at this point. It looks like I'm going to need a new drive shaft either way. I ordered the manuals and will be getting into the C6 in the next couple of weeks. I'm hoping to learn more about this issue as I go along. This should be interesting..