Transmission Vibration between 30 and 45mph

[bassman1]

I've checked the rear axle and the prop and they seem ok ,the clutch was changed after recent engine rebuild the vibration is still the same with the new clutch as it was with the old ,so i dont think its that, the flywheel was skimmed and balanced with a new starter ring fitted about 3000 miles ago and this was fine with no vibration so i'm not sure its that either, i can accelerate smoothly with no vibration third gear is no problem through 30mph and as soon as i change to 4th gear there's a lot of vibration coming through the gearstick you can feel it through the car body , dip the clutch and it stops re engage 4th and it starts again,its not the wheels as the vibration is way more intense that a wheel imbalance or buckle and it would still be there if the clutch was depressed if it were. I'm fearing a gearbox rebuild is on the cards , is there an easy fix ? any advice ?

i recently found my rear top leaf had broken , i have replaced this now axle is all squared up and this has not solved it either .

[mogbob]

I doubt whether a gearbox rebuild would be a solution to the problem.It's more likely to be in the transmission /suspension / wheels area.

Where both rear springs changed when you discovered the broken leaf ? Did you replace the rubber pads and bushes at the same time , leaving the nuts finger tight....only fully tightening when the car ( and therefore it's full weight ) was back on the ground ? Dampers got oil in and nuts secure ?

Any evidence of the propshaft having been "balanced" in the past and the "weight" ( usually welded on ) having fallen off ? i.e. a clean'ish rectangular area on the prop somewhere.

UJ's nuts all tightened up, good and tight and no slop , when you hold either side of the joint firmly and try to twist ?
Evidence of the propshaft having been greased regularly or joints seized or partially seized.Does the yoke move / slide freely if you jack up the gearbox...ever so slightly to take the weight off the join.You didn't have to force it in when the gearbox was put back in, after the clutch change / If so you may have damaged the splines slightly.

Draft question I know, I don't mean to be rude but are the wheel nuts tight.That has been a problem I've come across with my son's car after a Main Dealer service.Swopping over the tyres on the rear would eliminate the tyres and you would have the opportunity to thoroughly look over both side walls for bulges.

Lots of possibilies I know but most solutions aren't going to cost you a fortune to put right.Give it all the once over with a critical eye and see what you turn up.
Good luck with it and let us know how you get on.
Bob

[bmcecosse]

So - if you do this speed in 2nd or 3rd gear - there is NO vibration? It's only there when you change into 4th? And at higher speed - say 60/70 mph - any vibration then??

[bassman1]

@mogbob the rear top leaf nearside was broken sometime between August and end of october when i noticed it , i have just fitted a pair of new springs , with polybushes and new rubbers by the u bolts , i fitted loose then tightened on the ground , i even went back yesterday and undid the nuts and moved the car backwards and forwards then tightened back up again just in case,the car is at the same height both sides and up nicely , i would expect the axle to be nicely square now ,the dampers have oil in and operate very well with plenty of resistence, the prop has sealed uj's and no play the gearbox was refitted by my mate who is a mk1 mini restorer and has his own repair business i doubt very much whether he'd have fitted it incorrectly. i'll check the uj's again but i couldnt feel any sideways movement , i didnt shove a lever/screwdriver in to see if there was any forward rearwards movement though, all wheel nuts tight.if it was wheel probs i'd have expected the vibration to continue whilst free wheeling . just thawing and drying out after fitting the springs not looking forwards to lying in the road again !

[bassman1]

@bmcecosse , hi , yup no vibration untill i change into 4th it eases off at around 45 to 50mph , i'm still running the engine in so i won't know if it continues vibrating beyond 50mph i dont want to take a chance on this engine , its a tad frustrating and one of those problems that can be a number of things, i was suprised to see the sealed uj's on the prop which had been painted with silver hammerite so could be a replacement or recon , there appear to be no tab weights missing. i have never drained out the oil from the gearbox just checked it was topped up with 20/50 ,its not a tight box it is a bit of a sloppy gearchange , but doesnt jump out , the reverse gear is a bit noisy but works ok.

[bmcecosse]

If it's only in 4th gear - could be internal gearbox, although normally - being a 'straight through' drive in 4th - it's the quietest of the lot! Is there definitely a bronze bush present in the tail of the crankshaft?

[DAVIDMCCULLOUGH]

Have you tried taking the 4 bolts out of the propshaft and turning it round 180 degrees?

When my halfshaft broke going to this 2013 national my friend said to mark which way the prop came off, I said it wouldnt matter as id never bothered on any of my other cars before. Once everything was back together I had a constant vibration above 40mph which went away about 55mph. When I got home I turned it 180 degrees and the vibration was gone. Hope yours is this as well!

[bmcecosse]

Yes - certainly could be that ^^^^^^ well worth a try.

[bassman1]

yeah i rotated the prop shaft 180 a few weeks ago hoping that might be the problem but it didnt solve the vibration. The Bronze bush is this at the gearbox tail end ?

[bassman1]

i've just checked through my pics of the engine rebuild and unfortunately i haven't a pic of the crank end i had the vibration before the engine was changed and still have it now , i didnt check tbh oh crap i have to take the bloody lot out again jeeeeesus h !!!

[mogbob]

Another thought, has the previous owner / owners put the gearbox supports back in wrongly ( after a clutch change / engine work say ) and your mate put it all together " as he found it ".
The supports are right and left handed.A swop may have put the alignment out, with intermediate gears functioning with just enough slack in the box internally,straining in top.
All the mounting rubbers OK and gearbox restraint cable in place ?
My mates Moggie had it's cable " disconnected " .A previous garage had cut it free for clutch change ...with bolt cutters ! Didn't bother to replace it ...left it unconnected, great ?

Bob

[bassman1]

So far i have a doubt as to whether there is a bronze bush in the end of the crank i bolted on the clutch myself but cant remember looking to check if there was one there, this means removal of the gearbox and clutch to do it , if i fit a new bush and reassemble and this still doesn't solve the problem and i have all of the mounts correct , then i just have to remove them all again and fit a new gearbox oh what joy , i wonder if the vibration will be caused by just that front bush or a combination of things , what a nightmare !

[bassman1]

spoke to my mate today and he confirmed that the gearbox cross member and mountings were fitted the right way round , my cross member has 'front' stamped into it. He has booked me onto his ramp on monday next , he has a snake inspection digital camera he can insert inside the bellhousing and thinks i should be able to see on the viewer whether the edge of the spigot bush is visible if it is fitted , fingers crossed wish my memory was better i just dont remember whether a new bush was fitted to the new crank when we rebuilt last doh !

[bmcecosse]

I'm not saying that IS the problem - but it certainly could be. Although I would think the clutch plate and the first motion shaft splines would hold the first motion shaft firmly enough in place. However - the bush does have a purpose, and should be there. I 'hae ma doots' that you will be able to get the snake in there to have a look - but worth a try. If it does -any chance of a picture from the viewer of the snake??

[kennatt]

As you say BM if the bush was missing the only time the first motion shaft could rattle about would be when the clutch was depressed,its held solid by the pressure/friction plates when in drive.. Sure its not simple wheel ballence,I would be having them checked out before pulling the box.

[bassman1]

hi Kennatt, its a much more intense vibration than wheel imbalance , i've had front wheels throw balance weights on my old victor and you could feel a definate wobble through the steering wheel this is a quite intense vibration through the gearstick and bodyshell off the car,and i'd be getting it at 30mph in 3rd as well , but its only in 4th gear , My Mate thinks if it was the spigot bush causing the problem then it would be apparent in all gear selections not just 4th gear , has to be eliminated though , i shall put a lever in the prop uj and give it a good going over just to finally put that one to bed , i'll try and remember pics of the snake while we're checking it over , just be glad to get it up on ramps for a change its doing my neck crawling around in the road !

[M25VAN]

As you say BM if the bush was missing the only time the first motion shaft could rattle about would be when the clutch was depressed,its held solid by the pressure/friction plates when in drive.

When the plate is held could it be off centre due to the bush missing and the shaft running a bit off line? I had a similar bad vibration problem at 50ish in 4th only (probably wouldn't get there in third ) Turned out to be badly worn rivets on the plate allowing it to move a few millimeters and I guess sometimes clamp off centre and cause bad vibration. Dipping the clutch a few times would cure it by it eventually catching it 'on' centre.

[lambrettalad]

Slipped springs on the cover plate ?

[bassman1]

i fitted a brand new AP clutch kit when the engine went back it in october so reckon thats not causing it , all will be revealed monday hopefully !

[bassman1]

put car onto the ramps today at my mates garage and found the rear UJ to have play in it i checked it by hand a couple of weeks ago and it felt tight , we checked by twisting and forwards rearwards motion as directed by the workshop manual with a lever i got up close with an inspection lamp and the movement was easily visible but only when using the lever, probably why it showed up in 4th only with more load on the higher gear, i will replace both joints , the front felt ok but i want to be 100% with it , hopefully this will eradicate the vibration, if not i'll check out whether the spigot bush is the problem , it was useful crawling around underneath i found i need a new rear offside bump stop welding onto the chassis rail in the wheel arch the original is a bit corroded and moves slightly when tapped with a hammer, but the rest of the car is clean as a whistle still. Overall i'm hopeful that the 'fix' will be a damn sight cheaper than a rebuilt box !