Late differential issues.

Late differential issues.

Author
Discussion

ClassiChimi

Original Poster:

12,424 posts

148 months

Wednesday 10th February 2016
quotequote all
I've got a sneaky feeling my diffs a bit sloppy, as much as it is to much power going through it i feel the years of slight shunting have taken a tole. I've not really experienced any other Chimaera on local roads etc so it's hard to know if I'm inventing an issue.
Replaced all driveshaft CV joints a few years ago and I've been gentle ever since but still on off throttle there's slack, is it just a trait or is my diff loose,, driving fast it's not an issue but slow stuff I have to be very careful as to not introduce judder,,, engines running bang on, no real shunting anymore since Ecu upgrade but that slop is still there, prop shaft UJ's greased and found to be strong and tight!
Waffle,,, my question
With the later cars if I was to jack one side off the ground and try to rotate a rear wheel ( in nuetral ) what should I expect to find in a good or bad diff.
How much movement of the wheel should I expect before it locks,,

Thanks in advance Alun smile

SILICONEKID345HP

14,997 posts

230 months

Wednesday 10th February 2016
quotequote all
Its probably going to be mapping. It can cause a slight shunt which travels down the drive train .







Brerabit

74 posts

106 months

Wednesday 10th February 2016
quotequote all
Without doubt fuelling/ignition problems can be responsible for the irregular issue of power i.e. shunting, hunting, surging etc. and these symptoms can exacerbate and even cause wear in the drive train. However, once that slack exists no amount of mapping is going to replace metal that’s been worn from the numerous components between the engine and the wheels. I’m in a similar situation to ClassiChimi; I’ve invested heavily in getting my RV8 to behave in a civilised manner with a Canems EMS, Stage III heads and other induction mods and now it delivers as much wide range, smoothly delivered power as is reasonable to expect from a normally aspirated but significantly modified 4.0L engine and yes, the clanks and clunks I used to experience when trying to crawl along in traffic are considerably lessened - but even the slightest reversal of load immediately remains me that something isn’t as snug back there as it should be. So far I haven’t been able to trace it to the prop or drive shafts which leaves me wondering/worrying that it may be the diff. So I would also appreciate any straightforward check that would indicate whether the problem lies in that big chunk of expensive GKN hardware - or elsewhere.

ClassiChimi

Original Poster:

12,424 posts

148 months

Wednesday 10th February 2016
quotequote all
That's a relevant point but not really what I'm talking about, just that slack when reengaging gearbox off the clutch etc, just wondering what else I can play with on the car really,

I'm now able to drive in say 3rd gear from as low as 800 revs and gently accelerate with no shunting at all, slightest hint at 14-1700 revs but it's barely detectable and doesn't cause transmission clunking, it's now more on/ off throttle and gear changes that I find have to be matched perfectly but then that's half the fun I suppose,
It's more a question of if my dif is good rather than thinking it's bad!
The wheel turn test as I'll now call it, hah, so what should I expect, i can turn my wheel fairly freely for about 2/8 th of a turn, no real noise from the dif, could I use a slightly thicker grade oil in there or is that bad practice.
Just trying to perfect the car more smile

ClassiChimi

Original Poster:

12,424 posts

148 months

Wednesday 10th February 2016
quotequote all
Brerabit said:
Without doubt fuelling/ignition problems can be responsible for the irregular issue of power i.e. shunting, hunting, surging etc. and these symptoms can exacerbate and even cause wear in the drive train. However, once that slack exists no amount of mapping is going to replace metal that’s been worn from the numerous components between the engine and the wheels. I’m in a similar situation to ClassiChimi; I’ve invested heavily in getting my RV8 to behave in a civilised manner with a Canems EMS, Stage III heads and other induction mods and now it delivers as much wide range, smoothly delivered power as is reasonable to expect from a normally aspirated but significantly modified 4.0L engine and yes, the clanks and clunks I used to experience when trying to crawl along in traffic are considerably lessened - but even the slightest reversal of load immediately remains me that something isn’t as snug back there as it should be. So far I haven’t been able to trace it to the prop or drive shafts which leaves me wondering/worrying that it may be the diff. So I would also appreciate any straightforward check that would indicate whether the problem lies in that big chunk of expensive GKN hardware - or elsewhere.
Well put sir,, it's not just me then,,, Yep it's the last line of interest to me in developing the manners of the car, I suppose you can only really check by opening and looking at the dif gears etc,

Alan461

853 posts

130 months

Wednesday 10th February 2016
quotequote all
Hi Alun,
If you lift one wheel it won't tell you much because it's not an open diff.
Rotating the propshaft back and forth while in neutral will give an indication but there has to be some slack when cold or when it was hot it would cease up.
Can't tell you how many degrees of free play there's supposed to be, sure someone on here knows though.
A good diff specialist will be able to adjust it. Getting out and back in is fun.

Brerabit

74 posts

106 months

Wednesday 10th February 2016
quotequote all
I would have hoped that it was only necessary to open the diff to fix it - if it’s worn. I was hoping there was some way of comparing input to output and checking whether it was within tolerance - or is that difficult to determine without 250BHP of grunt at one end and a tonne of inertia at the other. In other words are simple attempts at feeling for slack by hand confounded by friction, limited slip mechanicals etc.

ClassiChimi

Original Poster:

12,424 posts

148 months

Wednesday 10th February 2016
quotequote all
I havnt got a lot of Tvr man funds in the kitty so I'm not really aiming on doing much now but it's something I often think about when driving, my dif is pretty silent so it's not something I'm expecting to go bang anytime soon,, maybe a tweak to the map may help but it's skirting the problem, it's that slack, I'll do the prop test again and update, maybe just change the UJ's at the next service and see what that does. I'm pretty sure my prop UJ's are original, 61,000 miles now so they've had a good innings. smile

Brerabit

74 posts

106 months

Wednesday 10th February 2016
quotequote all
I’m thinking along similar lines, change the uj’s as probably the cheapest potential fix and at 85k probably not before time - although I have tried to detect play and it’s not obvious. If that doesn’t fix it move on to the cvj’s by which time if it’s still clanking, it’s time to face up to the the inevitable and drop the diff out. After all it's not going to get any better when I move it up to 4.8L
No - it's not a typo...

OleVix

1,438 posts

147 months

Wednesday 10th February 2016
quotequote all
Ive had the same clunking and decided to do a full diff recon with a new LSD unit to swap. There is a quaife unit available for our BTR cone diffs from gearboxman. It should give superior traction, no maintenance and no cluncks! I purchased a 3.08 P/CW set from aussieland aswell, since its a nice upgrade while the diff is out

Alan461

853 posts

130 months

Wednesday 10th February 2016
quotequote all
3.08 porn, calm down..
I'll ask the diff man what the tolerance is supposed to be, mine is noisy at 54k, I've been avoiding the issue

SILICONEKID345HP

14,997 posts

230 months

Wednesday 10th February 2016
quotequote all
How are you getting on with the 3.08 ?

ClassiChimi

Original Poster:

12,424 posts

148 months

Wednesday 10th February 2016
quotequote all
Oly, I remember seeing that, keep us posted please,,,, I'm glad I raised it now,,
What I will say is I had all four drive shaft CV joints replaced and 3 new dif mountings within days of owning the car,,, drove our the garage and it felt exactly the same, top bush was foooked so I was right to change em wink but it didn't make any difference at all !
Combination of worn gearbox and dif, from the shunting, my car was owned by one person for most it's life, his money was spent paying it off I think! It's inherently a shunter I reckon, always suffered with it but only now has it been eradicated to a large extent,, it was never very bad but I also think the car spent a lot of its life in and around Edinborough so always stop start, gearbox itself feels tight and rather lovely but somethings not quite perfect.

OleVix

1,438 posts

147 months

Wednesday 10th February 2016
quotequote all
ClassiChimi said:
Oly, I remember seeing that, keep us posted please,,,, I'm glad I raised it now,,
What I will say is I had all four drive shaft CV joints replaced and 3 new dif mountings within days of owning the car,,, drove our the garage and it felt exactly the same, top bush was foooked so I was right to change em wink but it didn't make any difference at all !
Combination of worn gearbox and dif, from the shunting, my car was owned by one person for most it's life, his money was spent paying it off I think! It's inherently a shunter I reckon, always suffered with it but only now has it been eradicated to a large extent,, it was never very bad but I also think the car spent a lot of its life in and around Edinborough so always stop start, gearbox itself feels tight and rather lovely but somethings not quite perfect.
Gearboxman can do the total rebuild with quaife and 3.08... abit pricey but worth it!

Daz I blasted and painted the housing today, will put it together in the next couple of days... I'm guessing this diff will go nicely with the turbo smile

Bassfiend229hp

5,530 posts

249 months

Wednesday 10th February 2016
quotequote all
Brerabit said:
I’m thinking along similar lines, change the uj’s as probably the cheapest potential fix and at 85k probably not before time - although I have tried to detect play and it’s not obvious. If that doesn’t fix it move on to the cvj’s by which time if it’s still clanking, it’s time to face up to the the inevitable and drop the diff out. After all it's not going to get any better when I move it up to 4.8L
No - it's not a typo...
I have similar driveline "shunting" on mine - have just changed out the gearbox and have had the propshaft UJ's done too. I *SHOULD* do the driveshafts too but to be honest I just can't afford to - or more accurately I think that I need to concentrate spending on the bits that are most difficult to get to when the car is back together but easier to get to while the engine and transmission is all out.

I can change out the driveshafts and CV joints myself at a later date if necessary as I did them about four years ago - especially if I get round to changing the shocks and springs at the same time.

Phil

Dominic TVRetto

1,375 posts

180 months

Thursday 11th February 2016
quotequote all
Just in case - before you guys pull the diff out, check the propshaft itself...

I had the same from years of shunting in slow moving traffic and it had got really bad - thought it was the diff, but garage said when they had gone to remove the propshaft, all the bolts were totally loose and thats where the play was coming from, rather the diff.

May not be the same for you, but easy enough to check before commencing with the diff removal just in case...

HTH,


Dom

Clive-sz8cz

108 posts

103 months

Thursday 11th February 2016
quotequote all
Probably a totally erroneous piece of advice born of experience with Jag Mk 2. I had the engine rebuilt with a lightened flywheel and it was subsequently quite difficult to pull away in first and impossible to reverse smoothly due to horrible shunting. I put it down to the flywheel. After five years of this and two weeks before I sold the car I replaced the diff pinion oil seal and noticed the prop shaft was assembled 1 spline out so the two UJs were fighting each other. I lined up the UJs and the car was beautifully smooth - doh!