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Triumph TR6 - Driveline vibration

My 69 TR6 (w/o OD) has a bad vibration in teh driveline that starts around 52mph and gets worse with increasing road speed. I have had the main shaft rebalanced by reputable drive line shop, but no improvement. I have also rotated wheels front to back and swapped my spare for each of the road wheels one at a time, but gotten no relief. The vibration is road speed sensitive, independent of the gear used and occurs when under power or coasting. Can anyone give me a hint as to what could be wrong.
Geof Burns

Geof,
If it is only related to road speed, you can narrow down to differential to back wheels, and front wheels.
Since drive shaft is balanced, start with all the U joints (total 6 of them ).
Paddy
Paddy Kan


Geof,

Don't forget the wheel bearings..front and rear. As Paddy say's the 'U'joints might be a good place to start. With these hard to find problems I always start with the easiest things to do first. Especially if they are maintenance items. So, if you haven't done U joints and wheel bearings for a while it's probably a good time to do it. Maybe the problem will go away. I know the front wheel bearings are pretty easy. The rear wheel bearings appear to be a bit more difficult. I'm sure someone on this board has done rears. If after the "easy" stuff is done, and you still have the problem, you can narrow down the more difficult possiblities such as diff and trans (some parts are still turning when coasting out of gear....but low on the probability scale).

Good luck
Henry
HP Henry Patterson

Vibration analysis can be difficult. Here's a method.
At lawnmower shops you can get a 'reed tach', which has little fins that all vibrate at different frequencies. Place one of those somewhere on the car where it feels the vibration, and where you or a passenger can see it. When the problem is at its worst, note the frequency (rpm) of the vibration. Now, with some simple math, you can begin to hone in. If it's the same as the engine speed, then it's crank related; half that is cylinder head related. Work out the math to figure the frequency that a tire spot would hit the ground (I've lost those charts), but you can do it. Same for u-joint frequency, which of course will be very high, or if there is an off balance prop shaft. You may have a body harmonic vibration, which can be cured with a mass damper (something heavy glued to a strategic spot).
Good luck in your hunt.
paul

My brother in law had a similar problem with his TR6 and at about the same speed. He replaced the U joints and checked everything and, as I remember it, finally narrowed it down to worn splines in the rear axle shafts.

I think the new owner has likely tackled the problem by now. Hopefully yours didn't come out of Vancouver BC about 4 years ago???

SID
Sid Turner

Geof,

I,m currently troubleshooting a similar problem with vibration at speed, both under load and coasting although under load the vibration was harsher.

I discovered a severely worn driveshaft U-Joint and some minor to moderate wear on the axle U-Joints.

I'm now in the process of having all the U-Joints replaced and hopefully that will solve the problem.

John Parfitt
John Parfitt

I seem to recall a post in the archives describing a similar problem after reassembly of the drive shaft without care to ensure the proper relationship between the two universal joints.

Geof, join the BBS and search the archives for 'vibration'. The post titled 'U-joints' started December 17, 2001 contains a comment by Rick Crawford (on Dec 20) about this. I'm not saying this is your culprit, but if the DPO or his/her mechanic had the drive shaft out of the car and failed to re-install it properly, that could account for vibration.

Good Luck!
EC Smith

EC
Good point...now that I recall it. In the drive shaft there are 2 universal joints. If the UJs where replaced or the drive shaft seperated at the spline then you could have the UJs not synchronized. There is a proper word for this and STILL can not remember it. Simply they have to oriented exactly the same on either end of the drive shaft. If not they will be out of balance. The UJs on the axles can not be out to one another (either side of car) as the male and female splines here are "keyed". Ofcourse it has been said to check the UJs themselves. If they look original, then it is time to replace them. The drive shaft UJs are the easy ones to replace. The axle shaft UJs are the fun ones. Not bad to do but you need to pull the hub and this is the proverbial opening up of a can of worms. Also another thing to check is that all bolts are tight everywhere in the drive line..especially at the rear axle. There are bolts hidden under the plastic black boots (not the acordian rubber boots..this is the spline).
Rick C
Rick Crawford

Rick you are looking for the term phase,
Ujoints must be in phase.
Christopher Trace

Kinda like what my brain is suppose to be.
Thanks Chris
Rick C
Rick Crawford

This thread was discussed between 27/02/2005 and 02/03/2005

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