So, I've been having a bit of vibration at highway speed, sounds like a recent topic to me, and after following everyones advice on that post it looks like my extension housing bushing is toast.
I've located the parts that I need.
I suppose I have to remove the extension housing to get the bushing out. Is that correct?
Should I expect a flood of transmission fluid when I unbolt the housing?
thanks,
doug

 

I doubt very much the vibration is caused by the extension housing bushing (B3TZ-7A034-A). I'd be more inclined towards: an out of round driveshaft, the slip yoke, bad U-joints, broken rear spring, tires, or a bent wheel. If you have a 2 piece driveshaft, the center support bearing (D9TZ-4800-A = complete kit) is what I'd look at first.

 

Thanks Bill,
Suspension parts and wheels are all ok. One piece drive shaft. U-joints are not loose and are well lubed. Maybe the slip yoke? I was under the truck yesterday and had a lot of play in the extension housing bushing, I was able to wiggle the slip yoke shaft side to side a bit. I hope the output shaft is not worn out as well.
I still need to pull the drive shaft and see if it's straight and balanced. I guess I'm just trying to run the ole process of elimination routine on it. I'll find out everything it isn't and maybe I'll find out what it is.

 

If your transmission is leaking tranny fluid around your slip yoke then the bushing needs replaced. I just went through this last month on my '53 with a C6 mated to a 400. I have the slightest vibration on high speed deceleration. I looked at my slip yoke and it was a bit sloppy and fluid was leaking. So, I replaced the tail shaft bushing, the slip yoke and had the driveline rebalanced. I even fabricated a new tranny mount to get my angles more spot on with the rear pinion. Anyway, I took it out for a drive and the vibration is still there. I have not a clue what it is now. When I took my Grandpa out for a drive in it last summer (before I did the work) he said that vibe was from my engine mount design, they're rigid. Well, I wasn't convinced and you already heard the rest of the story...

Anyway, as to how much fluid you will lose when you remove your tailshaft. I was told it would be "not much". However, I ended up replacing 2 quarts when all was said and done and put back together. You will want a catch pan underneath. I think the angle of the transmission had a little bit to do with how much fluid I lost as well. I just set the truck up on jack stands so as to keep the truck level. Are you going to have a shop replace the bushing? I bought the bushing and a new seal (NAPA sells them together in a "kit") and took it to the driveline guy who also replaced my slip yoke and rebalanced my shaft. Anyway, I handed him the tailshaft and parts and he replaced the bushing and seal for $15. It's well worth it, because you really need a press to do this. Good luck and keep us posted with your results.

 

I chased a similar vibration that appeared exactly at 55 on a Camaro, had the rear end rebuilt, new driveshaft, new tail bushing. It turned out to be the rear planet carrier itself. These '60's, '70's, even '80's trannies are getting long in the tooth, and a rebuild generally doesn't replace anything but friction materials, seals, and other wear parts. The metal parts themselves get worn and are expensive to replace.

 

Rigid motor mounts can transmit every bad nuance into the cab. This is the way things were originally until "Floating Power" came along in the early 1930's. Floating Power refered to engines mounted on rubber. First car with it: Plymouth.

 

I'm pretty lucky. I work for a machinery manufacturer, and we have all the equipment to do just about anything. I'm thinking of just how many parts I can make out of stainless steel on our CNC equipment..........

 

Bill, the NumberDummy wins the prize for diagnosis of my vibration! Bent and or out of balance driveshaft. Now if only I can figure out a good prize for the winner. On that note, I think we should come up with a "virtual prize" for who ever gets closest to diagnosing a problem with someone else's truck via the forum. Anyone out there got that kind of skill? I'm thinking something simple like a bit map plaque or something.....
Anyway, thanks again for the advice Bill.
I took the drive shaft to a local big truck repair shop that does a lot of drive shaft work and they fixed it while I waited. He had to "straighten it a little" and added two balance weights on the shaft. Done in under 30 minutes and cost $50. Hurrah!

 

Glad to hear it was something simple -- thanks for posting the results, it adds to the knowledge base.