MOT brake test on rolling road ?

Messages
596
#41
In my case, I have come to "suspect" the LSD because of backlash in the drive train..
Whilst this is not confirmed the cause, after some discussion, what I notice is a shunting. It occurs at the back axle. I can sense it in all gears even if I dont feel the shunt, I hear it .
Lifting the car off the ground at the rear, selecting 1st (manual car), the wheel rotates a full handful before locking to the drive train....:eek:

I voiced my concerns to McGrath's when it was in for the service. (they also did a PPI for me) Not something I picked up on during a short test drive myself. Admittedly, I was relying on McGrath to focus on the potential issues, thats what i paid them for after all. They still shrug and say "they all do that sir"..:D
I cant believe it's how they would have been from the assembly line...which brings me here !
Reading that a clumsy MOT test can wring the diff out in seconds, its not a massive leap of logic to guess at the cause....
Confirmation to follow....
 
Messages
193
#42
In my case, I have come to "suspect" the LSD because of backlash in the drive train..
Whilst this is not confirmed the cause, after some discussion, what I notice is a shunting. It occurs at the back axle. I can sense it in all gears even if I dont feel the shunt, I hear it .
Lifting the car off the ground at the rear, selecting 1st (manual car), the wheel rotates a full handful before locking to the drive train....:eek:

I voiced my concerns to McGrath's when it was in for the service. (they also did a PPI for me) Not something I picked up on during a short test drive myself. Admittedly, I was relying on McGrath to focus on the potential issues, thats what i paid them for after all. They still shrug and say "they all do that sir"..:D
I cant believe it's how they would have been from the assembly line...which brings me here !
Reading that a clumsy MOT test can wring the diff out in seconds, its not a massive leap of logic to guess at the cause....
Confirmation to follow....
If anybody is ever looking for a top notch transmission specialist I would absolutely recommend Mackie's in Glasgow. They have rebuilt s couple of different gearboxes and axles for me. Especially on some of my big power yank autos where the usual answer is 'needs a new gearbox.' they are more than happy to do total strip and build and even custom work.
 

Evo Cymru

Junior Member
Messages
465
#43
Rear diff has a limited slip diff so I don’t get mine tested on rolling road and wouldn’t, not worth the risk.

The mot station I use have a gauge inside the car and drive it at a few mph to test brakes and handbrake.
Same for me and always did the same with the Integrale as well - not worth the risk for me...
 
Messages
3,944
#45
In my case, I have come to "suspect" the LSD because of backlash in the drive train..
Whilst this is not confirmed the cause, after some discussion, what I notice is a shunting. It occurs at the back axle. I can sense it in all gears even if I dont feel the shunt, I hear it .
Lifting the car off the ground at the rear, selecting 1st (manual car), the wheel rotates a full handful before locking to the drive train....:eek:

I voiced my concerns to McGrath's when it was in for the service. (they also did a PPI for me) Not something I picked up on during a short test drive myself. Admittedly, I was relying on McGrath to focus on the potential issues, thats what i paid them for after all. They still shrug and say "they all do that sir"..:D
I cant believe it's how they would have been from the assembly line...which brings me here !
Reading that a clumsy MOT test can wring the diff out in seconds, its not a massive leap of logic to guess at the cause....
Confirmation to follow....
Yea your not the only one, excessive backlash on 3200 diff crown wheel and pinion is not a new thing
The clacking /shunting you experience is fairly common, some do it, some don't, even from new!

There basically an old school ZF multi plate diff, the excessive play can be easily adjusted out with shims, but you need special tools...

Dave
 
Messages
596
#46
Yea your not the only one, excessive backlash on 3200 diff crown wheel and pinion is not a new thing
The clacking /shunting you experience is fairly common, some do it, some don't, even from new!

There basically an old school ZF multi plate diff, the excessive play can be easily adjusted out with shims, but you need special tools...

Dave
This is another possibility considered...
Neither issue can be resolved without removing the gearbox, Im guessing ? How to diagnose the cause though...?
AV @voicey have said they would do the work with the box out of the car but otherwise not interested. Could be the offer I need. If I can get the thing diagnosed, and a 4post lift locally for the duration...

Grtzzz..!
 
Messages
3,944
#47
This is another possibility considered...
Neither issue can be resolved without removing the gearbox, Im guessing ? How to diagnose the cause though...?
AV @voicey have said they would do the work with the box out of the car but otherwise not interested. Could be the offer I need. If I can get the thing diagnosed, and a 4post lift locally for the duration...

Grtzzz..!
If the diffs at fault there's no need to remove the gearbox, I'm betting voicey has never taken a old 3200 diff apart before... might be wrong though!

In the old days Maserati service would say just fit a new unit and charge the customer accordingly, about 3k with labour

That was fine when the cars were still worth 40 grand!

Dave
 
Last edited:

spn

Junior Member
Messages
46
#48
If the diffs at fault there's no need to remove the gearbox, I'm betting voicey has never taken a old 3200 diff apart before... might be wrong though!

In the old days Maserati service would say just fit a new unit and charge the customer accordingly, about 3k with labour

That was fine when the cars were still worth 40 grand!

Dave
Doesn't Tim have a 4200? In which case the diff is on the back of the gearbox.

Cheers,

Simon
 

spn

Junior Member
Messages
46
#49
In my case, I have come to "suspect" the LSD because of backlash in the drive train..
Whilst this is not confirmed the cause, after some discussion, what I notice is a shunting. It occurs at the back axle. I can sense it in all gears even if I dont feel the shunt, I hear it .
Lifting the car off the ground at the rear, selecting 1st (manual car), the wheel rotates a full handful before locking to the drive train....:eek:

I voiced my concerns to McGrath's when it was in for the service. (they also did a PPI for me) Not something I picked up on during a short test drive myself. Admittedly, I was relying on McGrath to focus on the potential issues, thats what i paid them for after all. They still shrug and say "they all do that sir"..:D
I cant believe it's how they would have been from the assembly line...which brings me here !
Reading that a clumsy MOT test can wring the diff out in seconds, its not a massive leap of logic to guess at the cause....
Confirmation to follow....
If you just have backlash and no grinding or clunking then I suspect the problem is with too much backlash in the crownwheel and pinion either due to wear or bad assembly at some point.

If the gears in the LSD were broken it would almost certainly clunk badly and possibly seize. If the plates were worn then you'd only notice it when one wheel loses grip or when cornering, not as drivetrain shunt.

The locking wheel you describe could well be the LSD pack working as it should, the multiple turns may just be required because the load on the diff is far lower than when it's being driven. Interestingly the 4200 has more diff locking action on power off than power on.

Either way, it's worth getting it looked at if it's bothering you.

Cheers,

Simon