what to do if you get tailshaft shudder?

[400ZED]

this is in a zed car independant rear axle behind a 341 slip yoke
All in and running but i think i have a shudder coming from the tailshaft at around 80k + under power. probably running my shaft to straight i was thinking. any other thoughts. it is running near as to the line of the old one which did not make any shudder ( except one realy big one ). but is is pretty straight i am just trying to sort out these problems before i can get out there and see what it has got.
some of you must have had experience with this problem.

 

[R-Jay]

what do you mean by tailshaft shudder? is this where there is heaps of movement in the rear end???
if you're talking about axle tramp, then yeah, i had this problem with my 180sx before... i put on some new diff cradle bushes (polyurethane ones) and that fixed her right up.... got heaps better launches after that too...

RJ

 

[Lexurious]

Was the t/s balanced before it was installed? What about play in the uni's. I assume all the bolts are the same this time. lol also check the input shaft on the diff for play.

 

[Zuffen]

I think we could take it as a given that the shaft was well balanced before it went in. 400ZED seen shaft problems before.

I do lean toward a mounting problem. More the mounting of the diff or gearbox. Are the mounts seriously strong and not allowing any movement?

I had a race car many years ago that had the rear gearbox mount fail and like 400ZED it literally tore the gearbox in half, didn't finish the race either! Even a few millametres of movement is enough to get things moving around and once the shaft steps out of true you will almost need to stop to correct it.

I would also not discount your rev limiter problem having some effect here. You have two problems that could interelate. I would sort out the Wulf first then the shaft.

 

[400ZED]

cheers zuffen the shaft is balanced new mounts all round and the best bolts i could buy.
The wolf rev limit at five could it be the spark blowing out ( i know nothing about this at all just wondering A what does flame out do and B could it be happening to me)
the wolf runs beautifully till five which is not where the shudder is ( by shudder i mean the tailshaft is vibrating and transfering throught to shaking the entier rear end not a lot but it does not instill confidence.) so i don't think they are related but if i combined them at the same time ie 80-km/h and 5000rpm it might get really ugly all over again.
I think you are right with the mounting problem i am looking at spacing the back of the diff down to increase and match the angles of front and rear uni's which look fine as does diff

 

[LEXUSV8NZ]

The only times i have heard about the spark plugs being blown out have been when running high amounts of boost, with this blowing the spark out (but this was over 1.5bar)
You could try to close the spark plug gap up to make sure that it isnt that causing it(And if it is you may have to look at a more permanent fix)
Hope this helps

Logan

 

[400ZED]

Cheers lexusv8NZ i doubt that it the cause of the five thousand rev limit.

The tail shaft shudder: engine is on a 4 degree decline and the diff is on a 4 degree incline Equal and oposed spoke to the guy that made the shaft and he recomends between 3 and 6 degrees. so i am still no wiser as to why it shudders.any thoughts?

 

[Zuffen]

400ZED,

This may sound real dumb but.

Are the rear wheels balanced?

You have two separate issues.
1 a miss at 5,00rpm.
2 shaft vibrations at 80kmh.

The two do not seem to be related but could be.

Lets look at 2.

If it is always at 80kmh does it vary depending on road surface. It should be worse on rougher roads if it is wheel balance. It only costs $10.00 to have two wheels balanced.

The angles you are using are within tolerance IF they were the same way. You are looking at 8degrees of driveline "bend". I would certainly balance the wheels first then if that doesn't work try adjusting the pinion angle of the diff. Visit a 4x4 site to see how critical it is to those guys, and they drive at a snails pace.

Lastly is the engine running down the centreline of the car? Some swaps require the engine to sit at an angle across the car.

Good luck. Keep us posted.

 

[gianttomato]

I'd check the pinion angle. Buy a magnetic roofing protractor and measure the angles from vertical of the engine pulley and diff pinion face. With the IRS diff being rather solidly mounted in the diff cradle, you'd probably only want a maximux of 2-3 degrees of pinion angle.

 

[400ZED]

BENT PINION FLANGE! It is nver any thing simple with me all fun and games in my gararge.
so if i can get that dam tight nut off i will get it machiened put it back on and see if the shaft is bent.
thanks for you sujestions. as for the 5000 limit toock it to the tunner and it revs to 7000 (where the limiter is set) and he won't tell me exactly what it was. said there were a few problems. dam these motors sound nice up there.

 

[LEXUSV8NZ]

he won't tell me exactly what it was. said there were a few problems. dam these motors sound nice up there.

Is this the same person who set it up originally?
Sounds like a cock-up to me
Good to hear everythings slowly working out for you

Logan

 

[400ZED]

slowly! but it is getting there
no it's not the same guy who set it up originally.
I set it up then a tunner had it for a while who did bugger all other than push my car into something
It was then tunned by the guy that was in it when the tail shaft let go who it went back to yesterday and he fixed the limit thing. he said it was a few things some hardware nd some software. He is a good guy it does kinda sound like a cock-up


i am just off to look at a viscous lsd and cv set up to see if it would be a hard conversion to adapt the cv's to the companion flange as the diff bolts in but the half shafts don't. a stright bolt in used clutch pack LSD is $1200 where a viscous is ~$200
any one reckon cv' would be better than uni's?

cheers