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Play in Vitesse Diff


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Hi all

I have been trying to find the source of a low tone whirring noise and vibration on the Vitesse, start to feel it after about 40mph. I mentioned it on here a while back. I can feel the vibration through the floor, and if I rest my hand on the rear tunnel. I have a sense that its coming from the rear. Tracking this down is not helped as the body is solidly mounted to the chassis. My first thought was that the exhaust was vibrating on the chassis, or prop out of balance. Had all four wheel in the air today, exhaust is fag paper close in a couple of places, but couldn't get it to touch the chassis, so ruled that out. I have a couple of cotton reel rubbers mounting the rear of the exhaust system to the diff, and wondered if these were a bit to firm and transmitting some exhaust vibration, but that wouldn't account for the whirring noise. Prop is a new, wheels were balanced in the past, and new wheel bearings all round. I have TLD sliding rear drive shafts, both as new.

Whilst pulling on one of the diff quarter shafts I can just detect an tiny bit of up and down movement. The shafts are under load with the spring at the moment but thinking it could be the bearing that is the source of the vibration.

Thing is I always felt that the diff was good. When I first drove it the one and only time around the block 16 years ago I remember thinking how quiet and smooth the drive felt. It did have rotoflex rear end at the time so the doughnuts were probably more forgiving than a sliding spline solid shaft.

Not looking forward to removing everything, but be worth it if this is the cause of the vibration.

 

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Blimey....... look at the secondaries on that!

If you can feel play in the quarter shaft bearing..... it’s not well.

Should be fairly easy to get out with the sliding spline shaft?  Getting the bearing off the quarter shaft can be a challenge.....

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Yep long secondaries, whether it actually helps with performance, cant really gauge at this point. Goes well when I put my foot down, but makes a lot of noise with this configuration and Bastuck back box. Problem with this set up is I can't ad a centre silencer! Probably look at the back box stuffing at some point as you suggested.

Definitely felt a tiny amount of movement, and pretty sure it wasn't the driveshaft UJ moving. Once I take the spring tension off I should be able to tell for sure. Hope it is the cause, save more head scratching.

Intention has always been to put the car on a rolling road,  with a standard engine, other than exhaust and carbs, and then go from there,  but have been holding off until I sort out the Vibration.

Thanks for the link John. Their explanations do point more to a diff problem than wheel bearing in my case, so hopefully on the right track!

Edited by Mark
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Surely with a Roto rear and sliding spline shafts, there shouldn’t be any tension at that point anyway? You should simply be able to unbolt the UJ from the diff flange, even if you can’t move it far enough out of the way to be useful without suspension dismantling.

FWIW, my prime suspect remains the propshaft. I have never had a small chassis Triumph that didn’t have a propshaft rumble and that includes new, purpose built, balanced and rebalanced. It probably telling me something about my driveline angles but on the Vitesse at least I got around it by balancing on the car.

Rear wheel balance shouldn’t be overlooked either. When swapped wheels on Chris’ Spit recently a high speed rumble we’d taken to be propshaft related suddenly went away.

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I'll have a go, but from memory with the weight off the wheels the driveshafts wedge hard against the chassis, and bolting them back up to the diff could be difficult, but I will try that way first.  I was going to replace bearings on both quarter shafts. With the rear of the car up in the air on ramps I could see a trickle of oil dripping out of the nose of the diff, so possibly a seal gone.

My first thought was propshaft, but as it was made up for the car I assumed it would have been balance, big specialist driveshaft place with all the gear, but maybe I shouldn't assume.

I did wonder about propshaft angle, and didn't give it a thought when I fitted it,  but looking at it yesterday it looks pretty level between box and diff.

If I hadn't felt slight play in the diff I would have got the propshaft balance checked first, maybe I still should, means dropping the exhaust to get the prop off which will be a job on my system.

Wheels have weights on, and I did get them balanced a couple of years ago, but maybe I've lost a weight, I'll swap fronts with back and give it a drive before I start taking things apart.

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Had a sort around and found some diffs that I had put to one side over the years a couple of 38.9 and one 3.63. Not sure of the condition but they all feel OK with no obvious faults. Going to take a chance and replace the one on the car Just to rule it out as the cause of the vibration.

Released the rear spring from the diff and vertical links and unbolted the drive shafts and prop and started to remove the diff mounting nuts and bolts.

I confirmed that there is a bad oil leak from the nose of the diff, then when undoing the nearside front diff mounting nut I saw that the ear of the diff was wedged hard against the chassis. Checked the O/S and there is a about 1/8'' space. Initial thought was that the diff mounting bracket was bent.  I checked the front chassis mounting stud was true and straight, which it appeared to be, so went ahead and fitted a replacement diff.

Same problem. The front N/S ear of the diff mounting is hard against the chassis.

This could possibly be the  source of the vibration I feel at speed, diff noise and vibrations as it moves about in its mounts rubbing against he chassis.

I may be replacing a good diff with an unknown, but it does have a oil leak that needs sorting.

Problem is whats causing the diff to interfere with the chassis?  I've never seen this before. I am using supposedly harder red mounts and they do sit tight in the diff cups, but they are a sloppy fit on the mounting studs, and don't push on and hold tight on the studs as the originals would. With the bolts through the rear diff mounts/chassis the N/S ear is a tight fit against the chassis, there is no flex when trying to lever it away , as the rear mounts hold it square. There is no damage on the chassis I can see, and the front chassis mounts are thick plate and look true.

Under the car with not a lot of room it was hard to see if the stud was square, but it appeared to be.  Looking at the photo, is it me or does it look as if the end is leaning back a nats?

Before I start whacking it with a club hammer, I'd appreciate yours thoughts, suggestion?

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I have seen this before and mine is the same given half a chance. I’ve always put it down to the front mount on the diff being bent, which they often are, but not sure it’s the whole story. Tweaking the front mount usually secures a miss, albeit a small miss.....

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Thanks Nick

Makes sense that it is the mount. What made me wonder was having the same problem with two different diffs.  But they are a heavy lump to carry and can imagine them being damaged at some point in their lives.

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Well its not the diff. Replaced with a spare after adjusting the n/s front mount with a club hammer. Some clearance was achieved, but not much. It was surprisingly easy to bend,  just a couple of light taps was enough. The front mount is a convenient hand grip, so being placed down hard on the opposite end could knock it out of true. 

Test drive was just the same. After about 40mph the the low vibration could be felt, more so under hard acceleration, 70mph is enough to make me want to ease up.

So I am hoping Nick's gut feeling that it could be the prop is right, and going to get it re-balanced.

Today I removed the exhaust, and briefly attempted to remove the prop from from underneath. The connection at the gearbox is right where the centre rails brace is, so I gave up. I am resigned to take the centre consul/stereo carpet etc out, which I have just recently put back in, and get to the prop from the top.

On the three diff mounts I checked, the n/s mount were all slightly further foward than the o/s when measured from the diff flange. The one I adjusted was significantly further forward but only gave marginal clearance when fitted.

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