Gearbox/Diff Problem
Discussion
Was having a great day out in the Griff today until some strange noises started....
First off was a clunk felt through the seat when disengaging power or reapplying power, even at a moderate cruise. Started to think, okay - something in the transmission line is worn/loose.
Then when accelerating or engine under load as a kind of knocking noise. Pulled over, engine sounded perfect, revved fine, no strange noise. Pulled off and after a short while the noise was back.
As I got home it sounded terrible, quite severe noise even when the clutch is in. Very bad sound when the power was applied and just minor clunking when clutch depressed.
So far I have checked that there are no loose driveshaft bolts, the prop at the diff end appears okay - not yet dropped the exhaust.
With the car jacked up the is some noticable play in the diff when rocking the wheels back and forth - probably about 5-10mm tyre travel. I'm not sure what the norm should be?
With every rotation of the wheel - there are two 'clunks'.
I replaced the diff oil about 500 miles ago with Castrol SAF-XJ (75w-150), so I've emptied it out this afternoon and it has gone a very dark brown colour - a lot darker than it went in. Checking the drain plug there were some very small metal flakes on the magnetic part, but only about 1/4 finger nails worth. There was about 1.2l of oil in total, I've had a minor leak - couple of drops on the floor after a drive, but nothing serious - I can't remember how much went in. (Will try to Google this - fluid capacity isn't in the 'Bible')
So, under the car - I've had the wife turning the wheel (she's a lucky lass), to try and identify the location of the clunking. With a screw driver handle pressed to my ear, touching the tip to the back end of the gearbox - it sounds like it's coming from there.
At the moment, I'm a little bit lost!! Going to remove the anti roll bar and drop the exhaust tomorrow - would appreciate any poiniters in the meantime!! (Or if any experts live near Rugby - there are some Beers on offer!!)
First off was a clunk felt through the seat when disengaging power or reapplying power, even at a moderate cruise. Started to think, okay - something in the transmission line is worn/loose.
Then when accelerating or engine under load as a kind of knocking noise. Pulled over, engine sounded perfect, revved fine, no strange noise. Pulled off and after a short while the noise was back.
As I got home it sounded terrible, quite severe noise even when the clutch is in. Very bad sound when the power was applied and just minor clunking when clutch depressed.
So far I have checked that there are no loose driveshaft bolts, the prop at the diff end appears okay - not yet dropped the exhaust.
With the car jacked up the is some noticable play in the diff when rocking the wheels back and forth - probably about 5-10mm tyre travel. I'm not sure what the norm should be?
With every rotation of the wheel - there are two 'clunks'.
I replaced the diff oil about 500 miles ago with Castrol SAF-XJ (75w-150), so I've emptied it out this afternoon and it has gone a very dark brown colour - a lot darker than it went in. Checking the drain plug there were some very small metal flakes on the magnetic part, but only about 1/4 finger nails worth. There was about 1.2l of oil in total, I've had a minor leak - couple of drops on the floor after a drive, but nothing serious - I can't remember how much went in. (Will try to Google this - fluid capacity isn't in the 'Bible')
So, under the car - I've had the wife turning the wheel (she's a lucky lass), to try and identify the location of the clunking. With a screw driver handle pressed to my ear, touching the tip to the back end of the gearbox - it sounds like it's coming from there.
At the moment, I'm a little bit lost!! Going to remove the anti roll bar and drop the exhaust tomorrow - would appreciate any poiniters in the meantime!! (Or if any experts live near Rugby - there are some Beers on offer!!)
Edited by jeboa on Saturday 24th March 19:00
The oil will go dark quickly if the oil you originally drained looked grim as you cant get the last 1/2 pint out near the nose of the diff, the new oil tends to wash all the diff case walls and gears thus staining the new CLEAN oil inc the stuff that dont drain, i agree you may have a fautly prop UJ not hard to diagnois once you give the prop a good twist & turn motion with a firm up & down motion thrown in & staying close to the joints, carry out the same treatment on both driveshafts too whilst checking diff security.
Edited by Simon says on Sunday 25th March 11:26
Thanks everyone. Okay ARB and exhaust off, no bolts loose on the prop and the hanger looks fine.
Yanking up and down on the prop I get tiny bit of movement and a slight noise at the gearbox UJ end.
I've removed the prop and I'm not sure if you should be able to feel play in the UJ's when off the car, but I can't seem to feel any play in them at all.
I think I have found the cause of the terrible noise though....note the new shiney marks on the UJ's and the exhaust silencer box.
It might be that when I fitted the new Y-Piece I have 'pulled' the box toward the front of the car on it's mounting rubbers.
This might sound like too easy a fix - but is it worth just knocking a slightly bigger dent in the box?!?!?!?
The gearbox rubber mounts are fine, all the silencer mounting rubbers are new (this could be pushing the box up a bit higher?). I fitted the SC polymounts (the ones in the metal cages) a while back and this could be contributing to pushing the front end of the engine up - and the gearbox end down slightly?
Yanking up and down on the prop I get tiny bit of movement and a slight noise at the gearbox UJ end.
I've removed the prop and I'm not sure if you should be able to feel play in the UJ's when off the car, but I can't seem to feel any play in them at all.
I think I have found the cause of the terrible noise though....note the new shiney marks on the UJ's and the exhaust silencer box.
It might be that when I fitted the new Y-Piece I have 'pulled' the box toward the front of the car on it's mounting rubbers.
This might sound like too easy a fix - but is it worth just knocking a slightly bigger dent in the box?!?!?!?
The gearbox rubber mounts are fine, all the silencer mounting rubbers are new (this could be pushing the box up a bit higher?). I fitted the SC polymounts (the ones in the metal cages) a while back and this could be contributing to pushing the front end of the engine up - and the gearbox end down slightly?
Well done that looks certain to be your problem, be a nice easy fix if that's everything, it would do no harm to just beat that area small area in a little more but your just as likely to achieve the same result lining everything up properly exhaust related or combination of the two maybe 
if that prop is fitted with grease nipples now is the time to give them some grease gun action 
a general purpose LM or CV grease will be just fine
if that prop is fitted with grease nipples now is the time to give them some grease gun action a general purpose LM or CV grease will be just fine Edited by Simon says on Sunday 25th March 21:23
lol, thats indeed a easy fix and pretty clear problem 
a bigger dent can help, but I guess when the exhaust gets warm the iron expant also...maybe better see if you can put it more away from the propshaft? by first loosen bolts from the exhaust and twist it a bit away from the shaft? together with the help of the points were it hangs in the rubbers.
difficult to explain in English
a bigger dent can help, but I guess when the exhaust gets warm the iron expant also...maybe better see if you can put it more away from the propshaft? by first loosen bolts from the exhaust and twist it a bit away from the shaft? together with the help of the points were it hangs in the rubbers.
difficult to explain in English
Thanks all. Will check the rubbers and position of the box tomorrow (as well as bash a bigger dent!). I have ordered two new UJ's - they're pretty cheap (£15 for two) - so I thought I might as well replace whilst I've got it all apart.
I'm still not 100% that there isn't a bit of play in the gearbox end, but have to admit I don't fully understand the internal workings. The end of the drive shaft has some wear marks on it - they're not grooves, just shinier than the rest of the shaft - is this normal?
I'm still not 100% that there isn't a bit of play in the gearbox end, but have to admit I don't fully understand the internal workings. The end of the drive shaft has some wear marks on it - they're not grooves, just shinier than the rest of the shaft - is this normal?
Changing the UJ's is sensible while you have the prop out those marks are just wear marks from the plain bush/bearing that supports the PS inside the gearbox and the oil seal marks the shaft too as the seal lip polishes the surface, looking at your pic you have nothing to worry about unless you have excessive up and down movement when the prop is positioned correctly into the back of the g/box of course, in my opinion you have found your problem already anyway 
those marks are just wear marks from the plain bush/bearing that supports the PS inside the gearbox and the oil seal marks the shaft too as the seal lip polishes the surface, looking at your pic you have nothing to worry about unless you have excessive up and down movement when the prop is positioned correctly into the back of the g/box of course, in my opinion you have found your problem already anyway Hi Simon, there is a little bit of up/down movement when the prop is in the gearbox. I am going to wait until I have the prop apart and put the shaft back in on its own to feel/see how much it is. I could be over sensitive - just trying to figure why the UJs would suddenly start to bash into the silencer (unless the exhaust has moved).
While the exhaust is off measure from the centre of the output shaft in the gearbox to, for example, the underside of the square chassis rail. Post your measurement on here and ask someone else who has the exhaust off, to measure in an identical way for a comparison. This may help determine if your gearbox is somehow lower than it should be. I cant see this being the case, but hey, no harm in checking.
TJC46 said:
While the exhaust is off measure from the centre of the output shaft in the gearbox to, for example, the underside of the square chassis rail. Post your measurement on here and ask someone else who has the exhaust off, to measure in an identical way for a comparison. This may help determine if your gearbox is somehow lower than it should be. I cant see this being the case, but hey, no harm in checking.
the gearbox mounts may have "sagged"Well, final troubleshooting analysis was the diff. Two things, the o/s bush was shot, but there is also an internal problem. Will replace the two side bushes - close inspection of the rear bush shows it to be in tip top condition - so won't be tackling this.
Dropping the diff was one of the more interesting jobs I have tackled - up on axle stands, lots of spanners, wobbler adaptors and socket combinations eventually let it free. Not a job I'd like to have tackled single handled, so welcomed the help of a good friend! Used the tried an tested method of removal - loosened all bolts then bench press, twist sidesays and lower onto chest - followed by snake shuffle backwards from underneath car. Will need an alternate method for refitting!!!
Dropped the diff off today at CTS for diagnosis, but looks like it may be a Crown/Pinion problem - which is going to be expensive - if the parts are even available (GKN Diff)!!!
Two questions for the experts!:
1. For the bushes, I have seen a couple of threads on polybush replacements, etc. But I think my mount is the 'thinner' type that the polybushes won't fit into (1994 car), I think the standard replacements are about £26 each at Power - any recommendations?
2. If the worst comes to the worst, whats involved in swapping to a BTR diff - new front (nose) brackets??
Dropping the diff was one of the more interesting jobs I have tackled - up on axle stands, lots of spanners, wobbler adaptors and socket combinations eventually let it free. Not a job I'd like to have tackled single handled, so welcomed the help of a good friend! Used the tried an tested method of removal - loosened all bolts then bench press, twist sidesays and lower onto chest - followed by snake shuffle backwards from underneath car. Will need an alternate method for refitting!!!
Dropped the diff off today at CTS for diagnosis, but looks like it may be a Crown/Pinion problem - which is going to be expensive - if the parts are even available (GKN Diff)!!!
Two questions for the experts!:
1. For the bushes, I have seen a couple of threads on polybush replacements, etc. But I think my mount is the 'thinner' type that the polybushes won't fit into (1994 car), I think the standard replacements are about £26 each at Power - any recommendations?
2. If the worst comes to the worst, whats involved in swapping to a BTR diff - new front (nose) brackets??
jeboa said:
Well, final troubleshooting analysis was the diff. Two things, the o/s bush was shot, but there is also an internal problem. Will replace the two side bushes - close inspection of the rear bush shows it to be in tip top condition - so won't be tackling this.
Dropping the diff was one of the more interesting jobs I have tackled - up on axle stands, lots of spanners, wobbler adaptors and socket combinations eventually let it free. Not a job I'd like to have tackled single handled, so welcomed the help of a good friend! Used the tried an tested method of removal - loosened all bolts then bench press, twist sidesays and lower onto chest - followed by snake shuffle backwards from underneath car. Will need an alternate method for refitting!!!
Dropped the diff off today at CTS for diagnosis, but looks like it may be a Crown/Pinion problem - which is going to be expensive - if the parts are even available (GKN Diff)!!!
Two questions for the experts!:
1. For the bushes, I have seen a couple of threads on polybush replacements, etc. But I think my mount is the 'thinner' type that the polybushes won't fit into (1994 car), I think the standard replacements are about £26 each at Power - any recommendations?
2. If the worst comes to the worst, whats involved in swapping to a BTR diff - new front (nose) brackets??
Hi jeboa, I went through the same as you the end of last year (I posted a thread then). My Crown Wheel and pinion were shot along with all three seals and output bearings (hence the really noisy diff). Bernie at CTS done me proud on the refurb (GKN diff), and John Reid of Grantura Engineering sourced a mint crown wheel & pinion for about £100 delivered to Bernie. Give John a call, I can't promise he will have anymore though. Anyway the bushes; after speaking with several people in the TVR trade I got mine from David Gerald TVR, he has the smaller size type for the GKN diff mounts, he also recommended the standard 'metalastic' type (which I bought from him and fitted) as his comment was 'unless you are doing competition work, the polybush type are not necessary and are a lot harder!Dropping the diff was one of the more interesting jobs I have tackled - up on axle stands, lots of spanners, wobbler adaptors and socket combinations eventually let it free. Not a job I'd like to have tackled single handled, so welcomed the help of a good friend! Used the tried an tested method of removal - loosened all bolts then bench press, twist sidesays and lower onto chest - followed by snake shuffle backwards from underneath car. Will need an alternate method for refitting!!!
Dropped the diff off today at CTS for diagnosis, but looks like it may be a Crown/Pinion problem - which is going to be expensive - if the parts are even available (GKN Diff)!!!
Two questions for the experts!:
1. For the bushes, I have seen a couple of threads on polybush replacements, etc. But I think my mount is the 'thinner' type that the polybushes won't fit into (1994 car), I think the standard replacements are about £26 each at Power - any recommendations?
2. If the worst comes to the worst, whats involved in swapping to a BTR diff - new front (nose) brackets??
By the way, getting it back is a pain unless you have a good mate, patience, a reasonable trolley jack and be prepared to try more than once. I found putting it on a trolley jack with one of the output drive flanges facing up, jack it into the space, carefully turn it around, place a bar across the front to stop the prop shaft flange swinging around and taking your head off, carefully jack up once inserted between the chassis rails so as you can get a bolt in the back mount, then carefully jack up the front, remove the bar, fit the side mounts with one of the M12 Cap heads in each bracket, whilst supporting it lightly on the jack fit other cap heads, torque up, fit locking nuts on back etc. I took the opportunity to fit new fixings throughout, including the drive shaft fixings (high tensile M10 Cap heads).
As you may have read in other threads, the old bushes are a pig to get out!!! All the best, Pete
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