Diff Backlash

[oleander]

Hi all,

I'm looking to buy a Tuscan. Tried a wonderful Mk3 earlier in the week.

But was surprised to hear some 'diff backlash' on so late a car (Sept 2006).

1. Is this normal: i.e. the soft, occasional clunk.
2. Do the earlier Mk1's have the same characteristic?

Edited by oleander on Friday 11th September 14:15

[Snaaakeey]

Quite common. They agricultural at best. Some are better than others but I know people who have had the dif refurbished and it made no difference at all.

[The Three D Mucketeer]

The Convertible and MK3s used the newer Dana Spicer M80 diff with a 3:46 ratio , because of the shunt , I changed within 2 years to the older M78 with 3:73 ratio and its perfect even now with a 4.5 Super Sport from Powers.Although in the Spec. TVR never supplied any Close Ratio gearboxes even on "S"s

[cliffords]

My MK1 did have a diff with a fair bit of backlash.
On investigation the prop shaft bolts were so loose you could turn the whole shaft a few mm before the diff moved .

[Modrich]

Could the shunt be dependent on final drive ratios on the M76 and are the Hydratrak versions any better?

[v8sag]

Reading through the Holden and GTO forums, it appears the m80 build quality wasn't the best, however rebuilds overcame any issues.

It wouldn't surprise me if the issue with the m80 in TVR's was, they used quite a long nosed 6 bolt cv pinion flange, followed by a 4-bolt prop shaft adapter. That flange was fine for a two-piece drive shaft running a centre bearing and a cv joint at the diff, but a one piece with a uj would be putting immense strain on the pinion bearing causing potential premature failure.

Edited by v8sag on Monday 14th September 22:43

[The Three D Mucketeer]

v8sag said:

Reading through the Holden and GTO forums, it appears the m80 build quality wasn't the best, however rebuilds overcame any issues.

It wouldn't surprise me if the issue with the m80 in TVR's was, they used quite a long nosed 6 bolt cv pinion flange, followed by a 4-bolt prop shaft adapter. That flange was fine for a two-piece drive shaft running a centre bearing and a cv joint at the diff, but a one piece with a uj would be putting immense strain on the pinion bearing causing potential premature failure.

Edited by v8sag on Monday 14th September 22:43

No .. The TVR prop shaft was different with the M80 3 bolt flange , I had to get a new propshaft aswell when I went to the 4 bolt flange M78.

If a customer complained , the factories way of fixing the problem with M80s was to revert to the M78s .

Edited by The Three D Mucketeer on Tuesday 15th September 12:34

[v8sag]

The Three D Mucketeer said:

v8sag said:

Reading through the Holden and GTO forums, it appears the m80 build quality wasn't the best, however rebuilds overcame any issues.

It wouldn't surprise me if the issue with the m80 in TVR's was, they used quite a long nosed 6 bolt cv pinion flange, followed by a 4-bolt prop shaft adapter. That flange was fine for a two-piece drive shaft running a centre bearing and a cv joint at the diff, but a one piece with a uj would be putting immense strain on the pinion bearing causing potential premature failure.

Edited by v8sag on Monday 14th September 22:43

No .. The TVR prop shaft was different with the M80 3 bolt flange , I had to get a new propshaft aswell when I went to the 4 bolt flange M78.

If a customer complained , the factories way of fixing the problem with M80s was to revert to the M78s .

Edited by The Three D Mucketeer on Tuesday 15th September 12:34

Are you sure? Here's the TVR m80 diff and the 6 to 4 bolt adapter. Anyway, this comes out a mile, which isnt the best for the pinion bearing. I was going to use this flange as I'm running a cv ended propshaft but went off the idea for reasons above.

[The Three D Mucketeer]

It was nearly 20 years ago and Heath(XWorks) and John Reid (Grantura Engineering) did it for me ... I had the old propshaft for years (but sold it last year) and there was an adapter with it. I guess because of the adapter the propshaft was shorter hence I needed the longer propshaft with the M78 without an adapter ...But I'm guessing.

[The Three D Mucketeer]

oleander said:

Hi all,

I'm looking to buy a Tuscan. Tried a wonderful Mk3 earlier in the week.

But was surprised to hear some 'diff backlash' on so late a car (Sept 2006).

1. Is this normal: i.e. the soft, occasional clunk.
2. Do the earlier Mk1's have the same characteristic?

Edited by oleander on Friday 11th September 14:15

It was 1st registered 1st Sept but I would imagine it was "built" between 1st Jan'06 and June-06 at the latest, since nothing came off the line after that
Probably sat in Drivestyle at Harrogate for a while.The last 4 digits of the VIN will give an indication of when it entered the order/build process.

[oleander]

So I understand that all the later cars (including the Sagaris) have this later diff fitted - with its notable degree of backlash.

And that the Mk2's are less prone, as they still had the M75 diff fitted...

[The Three D Mucketeer]

I'm not sure about early MK2 .. but I would bet virtually all MK2s have M80s certainly 2005 onwards

[Snaaakeey]

mine is a 2002 Tuscan with 50k on the clock. During the rebuild last year me and my Mechanic noted quite a bit if back lash. You could rotate the drive shaft a 10mm-15mm before engagement. The spider gears can be re shimmed. Spoke to a recommended chap ( Thegearboxman) for some advice and although he said it would have worn by now he also said they had a lot of play from new... Take what you will from it...