| Author | Message | ||
     Koby Millo New User Username: kobym Post Number: 5 Registered: 7-2011 |
Hi, 1976 Silver Shadow (LHD), which suffers from steering wheel vibrations, but only on acceleration when the gas pedal is pressed. Once the pedal is released, all is fine. Wheels balanced, bearings replaced both front and rear, prop-shaft rebuilt and balanced, front suspension rebuilt. Engine mounts looks fine. Any ideas would be appreciated. Regards, Koby | ||
| h_kelly Prolific User Username: h_kelly Post Number: 215 Registered: 3-2012 |
Hi Kobe, have you considered swapping front and back wheels just to rule out any problems with hubs, unlikely but inexpensive way to rule out same? P's I realise you gave balanced wheels. | ||
| Jim Walters Prolific User Username: jim_walters Post Number: 107 Registered: 1-2014 |
Do a search for "Detroit pots" and "rear springs" here on this site and Tee One Topics. It is likely your rear springs are sagged and/or the inner axle shaft joints (Detroit pots) are worn. SRH8505 SRC18015 SRE22493 NAC-05370 www.bristolmotors.com | ||
| Patrick Francis Frequent User Username: jackpot Post Number: 91 Registered: 11-2016 |
I have had just this experience and it was as Jim says, my rear suspension. On correcting the sag in the rear suspension, the vibration went away. I also swapped the half shafts (left to right)over as has been suggested on another thread. Hope this helps. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1799 Registered: 6-2006 |
Is the vibration speed related or engine rev related? I would describe detroit or drive train vibrations as coming more from the car through the seat of your pants. If it's through the steering wheel I would also look at engine mounts , especially front engine mount stop air gap. Also look for pipes or exhaust touching the body transmitting engine vibrations. | ||
| Patrick Francis Frequent User Username: jackpot Post Number: 92 Registered: 11-2016 |
I remember, when I had the problem, that I could feel the vibration on the steering wheel, but it was not the unbalanced wheel type of vibration, and it varied under acceleration and deceleration and speed combined. I also found it was worse with the car loaded, because my self levelling was not working at the time either, so the half shaft angle exacerbated the problem. As Paul rightly says, mounts etc can also be the cause. I check mounts by putting car in Low gear with my foot (hard) on the brake and prodding the accelerator with someone watching the engine. Again the same in reverse gear. Hope this helps | ||
| h_kelly Prolific User Username: h_kelly Post Number: 216 Registered: 3-2012 |
Hi, just wondering if a brake roller test rig might rule out front/rear vibration cause. Ie rear, the drive,trans,etc ..front roller test might isolate vibration to front of vehicle etc etc.. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 1295 Registered: 9-2004 |
Don't think the brake roller tester would get up to the speed needed, a rolling road dynamometer would but not really suitable IMO. Have had this on cars tyres that have been stood then balanced up Dynamically, when the tyre heats up and settles to its true configuration the vibration returns, more so with a steering rack. Just a thought. | ||
| Koby Millo New User Username: kobym Post Number: 6 Registered: 7-2011 |
Hi, Thank you all for the enlightening comments. The proposal to swap LH & RH half-shafts certainly makes sense, though I have to point that the Detroit pots were refurbished. Another point to mention: the vibration happens at various speeds, but only when the gas is pressed. Also - no problem when everything is cold, but once the car warms up, the vibration begins. does it bring any additional advise ? Thanks and regards, Koby | ||
| Patrick Francis Frequent User Username: jackpot Post Number: 95 Registered: 11-2016 |
Hmmm sounds like it might be engine? Running smoothly with choke on, then rough as engine warms and choke stays on?? Just a guess, but have you checked choke goes off when engine is warm? | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 1297 Registered: 9-2004 |
Had this sort of problem with a Triumph Stag with a suspension bush worn but not enough to give the usall clonk. This allowed the hub to run out line with the drive shaft UJ under load causing a vibration. The vibration was felt through the car but not on the steering! Is the car fitted with a steering rack if so from memory the rack has adjustable dampener. This can need adjustment if all else has been carried out. Have known the steering go light on exceleration with the trim hieght low at the rear King pin inclination effect. | ||
| John Beech Grand Master Username: jbeech Post Number: 359 Registered: 10-2016 |
808-type keychain cameras connect with a USB cable and are so cheap you can zip-tie several in place at once to observe for vibration. https://www.walmart.com/ip/Mini-808-Car-Key-Chain-Micro-Camera-HD-720P-H-264-Pocket-Camcorder-F5/263002236#about-item More expensive, this one comes with a yellow composite video-out connector, which allows plugging into the back of any television for replay: https://www.amazon.com/808-Lens-Camera-Pocket-Camcorder/dp/B00CTO0Y06 | ||
| Patrick Francis Frequent User Username: jackpot Post Number: 96 Registered: 11-2016 |
Hi John If memory serves, was it you that discovered your propshaft vibrating by using this method? Apparently the problem was the propshaft was 180 degrees out? Clever idea! Patrick | ||
| John Beech Grand Master Username: jbeech Post Number: 362 Registered: 10-2016 |
Nope, not me, but nevertheless, I agree it's a clever idea ;>) | ||
| Patrick Francis Prolific User Username: jackpot Post Number: 107 Registered: 11-2016 |
Hi Koby Any luck with finding the source of the vibration? Patrick | ||
| Koby Millo New User Username: kobym Post Number: 7 Registered: 7-2011 |
Hi Patrick, On a closer inspection, I found that my "UR72000 COMPLIANCE MOUNT" were worn, and it might cause a vibration of some sort in the front suspension. I'm going to replace them soon and I'll see if it solves the problem. If not, I guess I'm going to swap the 2 rear "Detroit pots". I'll update you all. Thanks, Koby | ||
| Patrick Francis Prolific User Username: jackpot Post Number: 112 Registered: 11-2016 |
OK thanks. Good luck Koby. |
