Keith Scotch Posted May 19, 2022 Report Share Posted May 19, 2022 My GT6 Mk 3 ( non-rotoflex) is running fine until I get to around 50mph when I start to get a vibration from thew rear of the car which gets worse and noisier as speed increases. The tyres and rims are fine and balanced. I can't see anything obvious wrong with the wheel bearings or UJs. There doesn't seem to be any excess play or clunks. I'm left thinking that it could be prop shaft related (out of balance?) or maybe it is the bearings or UJs? Is there an easy way to track down the fault? Have I missed something obvious? Don't want to mess around removing the prop or wheel bearings if they're ok. Thanks Link to comment Share on other sites More sharing options...
JohnD Posted May 19, 2022 Report Share Posted May 19, 2022 Prop shaft possible, or else U/j . Get it up on wheel stands, look under, shake the prop shaft for looseness. Ditto all the suspension joints - a pry bar may be useful. Then run the car on the stands, while observing it from a safe distance! Can you see prop vibration at the appropriate speed. (This requires careful thought for a safe test!) There is a method to 'rebalance' the prop, by putting two jubilee clips on it, with the screws on opposite sides, so they balance. Then move ONE around. If vibration worse, move it the opposite way, until the vibration settles. THis isn't a quick procedure! Link to comment Share on other sites More sharing options...
dougbgt6 Posted May 19, 2022 Report Share Posted May 19, 2022 Keith, Before you start diving into the worst possible case scenario I would swap the tyres around. Just because they look OK doesn't mean they are. Doug Link to comment Share on other sites More sharing options...
Clive Posted May 19, 2022 Report Share Posted May 19, 2022 But experience suggests the orop us orientation suspect. My gt6 had an out of balance prop, made the car horrible 50-70mph. Current spit had a uj seize. Unbearable, but nonpayment in the uj, only obvious once dismantled. Changing the uj left the prop out of balance, so that was another job. If prop is the likely cause, find somewhere to fit quality ujs and rebalanced. Wheels are about the only other suspect, bearings and diffs don't vibrate. Bent driveshaft could. Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 19, 2022 Report Share Posted May 19, 2022 Keith pop it round to sunny luton and we can have a listen firstly props run at engine speeds wheels and drive shafts about 4 times slower so the frequency of the vibes is a good pointer to the culprit also if someone has had the prop apart the yokes must be aligned to each other at each end of the prop one spline error on the telescope will give problems so is it a va va room vibes or a round and roundy vibe ??? ie say the prop at 50mph is at around 3000 rpm the wheels are at 750 theres a big difference Pete 1 Link to comment Share on other sites More sharing options...
JohnD Posted May 19, 2022 Report Share Posted May 19, 2022 Hang on, Pete! The prop runs at a speed proportional to road speed, not engine speed, the proportion being the diff ratio. It also runs at a speed proportional to engine speed but that depends on which gear you're in. And the yokes that connect at each end have bolt holes spaced in pairs, so each can only be connected in one of two ways, not four. It is said that they were originally balanced in situ, and should be pop-marked before being taken off, so that they are reassembled in the same orientation, else vibration will occur. With two ways at each end that's 2x2 =4 possibilities, and while one is perfect, two are bad and the last is AWFUL! If you have had the prop off, then think about refitting it in different orientations. But the balancing was done by welding a small steel plate to the shaft, about halfway down. I don't think the plate was well protected against corrosion and can just rust away! Having said all that, my money is on a U/j fault. A pry bar should reveal which one. John 1 Link to comment Share on other sites More sharing options...
NonMember Posted May 19, 2022 Report Share Posted May 19, 2022 My GT6 had similar vibration. On investigation it turned out the sliding spline on the propshaft was shot. That may be fitted at the front, so not readily accessible, but it's well worth a check. Link to comment Share on other sites More sharing options...
Keith Scotch Posted May 19, 2022 Author Report Share Posted May 19, 2022 Thanks for your advice chaps - much appreciated. Pete - I live in Flitwick so not far from Luton. I'll take you up on your offer of having a listen to it. Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 20, 2022 Report Share Posted May 20, 2022 13 hours ago, JohnD said: Hang on, Pete! Im just trying to make the vibration frequency into a more understandable where it coming from at 50mph Keith will be in 4th Ish and as Rob says the telescope can be badly worn maybe because it never travels , my Vit6 was appalling when we got her . Pete Link to comment Share on other sites More sharing options...
JohnD Posted May 20, 2022 Report Share Posted May 20, 2022 12 hours ago, Keith Scotch said: Thanks for your advice chaps - much appreciated. Pete - I live in Flitwick so not far from Luton. I'll take you up on your offer of having a listen to it. Best idea so far! Pete will see you right! Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 21, 2022 Report Share Posted May 21, 2022 we will attempt a test run at Mondays Pub meet at the Raven first problem is .....getting me into a GT6 then getting out again Pete 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 26, 2022 Report Share Posted May 26, 2022 Just been out with Keith and its pretty certainly propshaft its comming off so we can have a look , this could be phasing .or telescope wear, unlikely a UJ its a high frequency kicks in at 50 quite hard /noisy but can be felt earlier at low speed all will be revealed sometime later think a trip to Bailey and Morris is on the cards Pete Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 26, 2022 Report Share Posted May 26, 2022 just looked at normal triumph supplies and yikes props have certainly gone UP a lot luckily im just looking not buying will have a gander at the prop before Keith jumps into deep wallet syndrome Pete Link to comment Share on other sites More sharing options...
Clive Posted May 26, 2022 Report Share Posted May 26, 2022 Dave Mac quoted me £195 recently, I doubt that included VAT..... Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 26, 2022 Report Share Posted May 26, 2022 yes the 150ish has jumed to over 200 maybe im just getting out of touch but after covid everywhere is playing price catch up Pete Link to comment Share on other sites More sharing options...
NonMember Posted May 26, 2022 Report Share Posted May 26, 2022 2 minutes ago, clive said: Dave Mac quoted me £195 recently, I doubt that included VAT..... That's still cheaper than I paid at Bailey Morris last month (for a GT6 prop). Link to comment Share on other sites More sharing options...
Clive Posted May 26, 2022 Report Share Posted May 26, 2022 Canleys are £218 incl. VAT, seems pretty good. HD version a bit extra. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now