Section : General

General Stag messages

Dreadful Rumbling Noise!

Posted By : Jason Matthews, 22-Jun-2007, 04:55pm

Hi. My stag has started making a dreadful rumbling noise. Its ok when pulling off, in first or second, and seems fine up to about 25 or 30 mph. By this time i've changed up to 3rd or 4th and in both of those gears theres a real deep growly rumble when accelerating and you can feel a shuddering in the car. If you lift off the noise seems to stop (although there is still a slight rumbling vibration, which may or may not be connected). As soon as you put any load on the engine/drive with your foot it starts up again. Once i'm up to about 50 i can cruise ok but the noise and vibration are there if i put my foot down. Any ideas?

Followups :

Dreadful Rumbling Noise!

Posted By : Jason Matthews, 22-Jun-2007, 07:44pm

I'm thinking the problem is most probably either in the propshaft or UJ. I've just laid under it and rocked the propshaft about and i get quite a clonking in the diff though. I'll jack it up and have a proper look tomorrow but any ideas in the meantime would be really helpful!
- Dreadful Rumbling Noise!
  
  Posted By : Chris Taylor, 24-Jun-2007, 07:16am
  
  If the car was of the Herald family I would definitely look first at the propshaft u/js. However, from what you describe, could equally be a collapsing diff pinion bearing. Replacing u/js is not too difficult and a DIY job. If you're lucky, you will not need it rebalancing either. Diff problems are however a rather more serious matter. I would drive with a knackered propshaft for short distances if essential. If however there is visible play in the diff input shaft, I would not drive anywhere as seizure of the diff will lock the rear wheels instantly.
  - Dreadful Rumbling Noise!
    
    Posted By : Jason Matthews, 25-Jun-2007, 05:31pm
    
    Hi thanks for that. I tightened the gearbox mountings up at the weekend and the problem has improved a great deal. Now its fine in the first 3 gears, up to about 30. If i then engage 4th gear from this speed up I get the rumble, which you can feel in your seat. Its much quieter than it was, suggesting that maybe the vibrating 'box was maybe part of the problem, but still there at speed. At speed, if you lift your foot off the gas the rumble is still present but much quieter. Accelerate at all, and its instantly noisy. The noise in the diff that i described, you get if you grab the prop shaft and twist it. The diff clonks when you do this. I'd assume they all have some play, and that they all clonk a bit when you rotate the propshaft, but I'm only guessing. There is no 'side to side' play here. Don't know if this has made things clearer or muddied the water for you!
    - Dreadful Rumbling Noise!
      
      Posted By : Mark Hammond, 25-Jun-2007, 05:37pm
      
      Have you checked the gearbox tailshaft housing for cracks? I had this on a Triumph 2000 once. If the car has O/D (which it probably has, being a Stag) then this won't apply. It could be U/Js) or just old fashioned propshaft imbalance.
      
      Mark
    - Dreadful Rumbling Noise!
      
      Posted By : Chris Taylor, 25-Jun-2007, 06:40pm
      
      Well, the diff isn't about to instantly disintegrate. They all have play in the way you say, and will "clonk" to a certain extent when you reach the limit of backlash in each direction. It's all a question of degree, and you really need to get someone with experience with this sort of diff to check it and see if they think it excessive. (Same type of diff used in 2000/2.5 saloons and Tr4a-Tr6, as well as Stag).
      I am intrigued as to your comments about being worst in 4th gear. While I would now suspect propshaft balance, they are almost entirely dependent on speed, and you should get the same problem at the crucial speed in any gear. And while that might point to the gerbox itself, in general gearbox problems are LESS in 4th where there is direct drive and no gearwheels or the layshaft are involved in power transmission.
      - Dreadful Rumbling Noise!
        
        Posted By : Jason Matthews, 26-Jun-2007, 07:35am
        
        I'm sorry guys, it's a bit of an odd one i know! The rumbling is def more apparent in 4th gear, although I always try not to over-rev the old girl in lower gears and may need to see if it appears at the same speed in 3rd. Really seems to start up about 25-30mph so is related to speed. I'm beginning to wonder if it may be propshaft imbalance as you suggest. The propshaft ujs seem to be fairly tight. I did notice that (when the stag was converted to 2.5PI power I assume) the exhaust is bolted directly to the rear of the gearbox, as opposed to on rubber mounts. Don't know if this is true of 'normal' stags but I've visions of the whole propshaft, gearbox, exhaust vibrating due to a propshaft imbalance. As the cheapest option to fix though, it may be just wishful thinking!!