a bit of drivetrain help needed

[170-3tree]

I have found the reason my car acts awkwardly while cruising around town, but now I must track down the source. It seems as though the drivetrain has entirely too much play in it. I know there is some play in the rear end, but how much should be acceptable. I can spin the rear yolk about five or so degrees without making the tires twitch. It seems like a lot to me, but I am not an expert on that part. How much should be in the transmission?
The car runs really well, but it just shakes like crazy at highway speeds and acts weird around town. I am having the crankshaft checked for balance right now and then it will be time to move on to the next step in figuring out this problem.

[rbohm]

it sounds like the U joints have gone quite bad, as has the rear end. i doubt the carnk has any balance issues.

[The Plankster Prankster]

i'm gessing he meant to say he was having his driveshaft checked for balance, as the crankshaft doesn't fit with the issue whatsoever.
as for the slop in the rearend, every rearend i've handled had a fair amount of slop as you describe. this always APPEARS to be excessive, but is normal.
also check the yokes on both the tranny and rearend for ANY non-rotational movement, as they should be tight on their bearings
U-joints are a VERY likely option, as rbohm mentioned. you may also want to check out your tires. a couple months ago i was driving Suzie, something felt weird so i stopped and found severe tire damage, leaving it so far out of balance i could feel it. check for bulging and other damage.
another thing to inspect for is loose hardware. awhile ago, my car "larry" just had a vibration at various times (you could see the dash vibrating up and down over 1/4"). problem was a couple of loose mounting bolts holding the front crossmember in place. such unexpected things can confuse the heck out of you!

can you tell roughly where this shaking is coming from: steering column, greater front end, greater rearend, one corner, etc. and what does "acting weird" look like?

[170-3tree]

Well I dropped the driveshaft off for balancing and the guy who I spoke with told me right off the bat that the front yoke was in need of replacement. He told me he is surprised it wasn't leaking a lot of tranny oil out the tailshaft. They will balance and replace u-joints (even though we just replaced those, standard practice). I hope that all of this will help a bit, but i'm not expecting much difference. Who knows.
The shaking is definitely coming from the rear end of the car felt mostly in the seat. I have checked the tires and rotated them so that should alert me to tire troubles if the shaking is not in the rear anymoe. By acting weird I mean honestly that it seems as though my driveshaft is flexing (like a section of it is rubber) a little bit. almost like there is too much space between gears in the drivetrain.

[fmartin_gila]

If the front yoke needs replacement, you may possibly need to install a new bushing in the tail housing of the trans also. Check how much clearance you have when you try a new yoke.

Fred

[170-3tree]

What does it take to instal that bearing on this transmission? I am thinking about digging up another one in better condition, or getting this transmission rebuilt, but I don't know what the best and least expensive option would be.

[The Plankster Prankster]

i don't remember what tranny you have, but on EVERY tranny i've worked on the tailshaft housing unbolts from the rest of the tranny easily. usually, the tranny mount mounts to the tailshaft housing, but it can be removed while still in the car, simply support the tranny with a jack, remove the mount (and possibly crossmember) to gain enough clearance, and unbolt the tailshaft housing, while expecting to lose some fluid.

as for changing the bushing itself, i'm not sure, but if its too involved, you could have your local tranny shop do it if you just bring in the housing and give them the details on it.

[fmartin_gila]

No need to pull anything but the driveshaft to change the rear bushing. There is a tool to insert into the bushing and expand to grasp it and pull it out. Then drive a new one in.

Fred

[66 Fastback]

Fred,
Isn't the output shaft and splines in the way of replacing the bushing?

I have always pulled the extension housing off. The bushing itself is cheap and you might also require a new gasket (or sealer) and some fluid. It is just a bit of labor involved in replacing the bushing.
Doug

[fmartin_gila]

No interferance by the output shaft. The tool slips in where the yoke would and expands out to grip the old bushing, then a jackscrew pushes against the output shaft end to extract the bushing. With this extraction tool and the driver for the bushing, the job can be done in about 15 minutes cause you don't have to mess with any of the mounts or removing & reinstalling the tailhousing. A great tool setup when doing fleet work as I used to do.

Fred

[The Plankster Prankster]

i learn something new every day... where do you find this tool

[fmartin_gila]

Most any of the mobile roaming tool trucks (Mac, Proto, Etc) serving fleet mechanics and dealership mechanics carry these type tools. I imagine you could have the normal stores (Napa, and such) order for you. There are a lot of tools out there to do a lot of jobs in very short order that Fleet and Dealership mechanics have used over the years that most people who don't make their living doing vehicle maintenance don't know about. On the other side of the coin is that most people only need some of these specialty tools once rather than over and over, hence it is not really economical to purchase these type of tools to do a one time job.

Fred