vibration on 3rd gear upchange - help

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bodmodbaby

New Member
Posts
64
Location
atherton near wigan
when i bought my 110 (1989 2.5td) i was told it had a noisy transfer box. i drove it and the noise was a whirring whining noise, but completely livewithable. and since carpetting the cab the noise virtually went away.
a week later i get some chirping from the drivetrain, intermittently when under power, and the speed of the chirp was relative to the speed of the wheels turning, gradually it got louder and more often.
the next thing that started to happen was loud knocking when setting off or changing up gears, this i thought was slack in the drivetrain so i checked all the UJs in the rear drive shaft as there was some play, but no play in the front. i regreased and reassembled and it was ok for a week, with no real wear visible on the UJs themselves.

now the most recent problem is when i build up speed, i get to third gear, around 27mph, i put the clutch in nice and soft, and as the clutch goes down to the floor and im inbetween gears, the rear wheels feel like theyre making the drivetrain kindof skip, and the whole rear end vibrates.

its very similar to the shake you get from an unbalanced wheel, or if the driveshaft was not evenly weighted for instance.

my thoughts are that this whole time the bearing that holds the rear driveshaft inside the transfer box has been wearing away, and now its worn to nothing, so much that when the drive is engaged and the rear wheels are under power, the torque of the drivetrain holds the entire assembly straight and true, and when not under power, or coasting, the drivetrain becomes loose and shakes, shifting its weight around in an arc like a skipping rope, causing the vibration.

first of all am i talking complete bull honky. im not a mechanic but will do my own work if needed, and i have more of a theoretical mind than a mechanical mindset???

if im right, or near enough to being right, what do i need to change.
does the transfer bo have to come out, or can i take the rear driveshaft out, and get the input shaft out of the transfer box with the worn bearing attached, and just replace it?
 
if there is a lot of play replace out out bearing ,checking oil by draining some out can show if a particular box has a problem ,as can running through the gears with t/box in neutral (everything in t/box turns except diff and output shafts
 
so still noisy with t/box in neutral ?

well in neutral its not the same noise, i say its loud but reli its a light whiring, if the door wasnt open with my head poppin out i wouldnt be able to hear it at all. its pretty insignificant.

but when driving i still get knocking on gear changes which i presume is the slack in the drivetrain, which i can deal with, using very soft slow gear changes and clutch action which has become the norm.
the major problem im having is the jumping skipping vibration. its definitely coming from the rear, and is happens just below 30mph when i put the clutch in to change to 4th, its almost as the rear wheels are driving over a cobbled street for a few seconds.

i dont know if its some sort of backlash, or binding.
anyway i checked the transfer box oil today, its just about level with the fill plug which i thought was ok, and i also did an unrelated engine oil change with a new filter. got myself a haynes manual aswell.

if its not anything to do with the transfer box or output shaft, i can only assume its some scientific reason that involves the most apparent wobbling of unblanced wheels happening at 27mph, and the coincidence of being always when i shift up to 4th, and also being magnified by the clutch being in.

im looking to fit some cooper st 33/12.5/15 on new modulars, which ive been assured will fit to a standard 110 with wider arches, i dont wana buy the wheels if the slight raise because of the tyre diameter is gona casue a worse problem with the angle of the driveshaft;

any more ideas?
 
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