General => General Discussion => Topic started by: scud on January 18, 2019, 19:55:27 PM

Title: Propshaft questions
Post by: scud on January 18, 2019, 19:55:27 PM
Recently 2-3k miles ago I replaced the propshaft dohnut rubber on my Xr's rear prop with a custom spacer that allows use of the still available Cosworth item and at the same time I replaced the center support bearing, the rear uj seemed fine at the time.

during testing after that everything was fine up to about 140mph, where some moderate vibration occoured that was hard to tell where it was coming from but did quieten quit alot if i went on the throttle and got worse backing off or just fethering it, but since i dont go that fast very often i didnt worry too much at the time as i said the uj looked fine and i recently rebuilt the front one.

then i broke an exhaust mount got it welded and found i had really bad vibs at 60-70mph which turned out to be the exhaust on the bumper .. mostly
After i sorted that i found, while testing the previous hard to pin down high speed vibration seemed to have moved to the 110-120 mph zone and gets slowly worse going faster but still changes with the throttle.
 so i had a poke around while fitting my accusump, and the center bearing had some signs of wear already, and there is some noticable play in the rear uj too not much but it moves by hand without much effort.

can anyone confirm my suspicions that this play in the uj and preamature wear in the center bearing is most likely the culpriit before i pull it all apart again ?

oh and can anyone tell me the size of the rear uj please
Title: Re: Propshaft questions
Post by: capri v8 driver on January 20, 2019, 19:31:10 PM
There should be no noticeable play the joints or in the center rubber. I would start to have the prop shaft balanced. I would also check the engine and gearbox mounts and the angle the engine/gearbox sits against the diff. With a sierra you want 0 degrees in the first prop shaft and no more then 5 degrees in the second prop shaft.
Title: Re: Propshaft questions
Post by: scud on January 29, 2019, 21:02:33 PM
yes ive got a new center bearing and spider, the engine and gearbox mounts are all new I will get the shaft balanced once they are all fitted, got a new diff mount to finish it off.

my prop is one piece, just one uj at the rear diff.

once I finish all the emergency jobs on my friends ST I will get on it