While the diff is out?

[jono]

...are there any other jobs or upgrades worth doing?

My Plus 2S is stripped bare and I have the Spyder chassis away being blasted and repainted in a nice grey as opposed to horrible orange.

The engine has been rebuilt to 135bhp spec with big valves and QED 360 cams and will be running on FI.

I am retaining the 4 speed box but the diff is currently being converted to 3.54 and the driveshafts to Sue Miller CV.

I think the diff casing is the stronger one but the torque rod holes are ovalised so I am having them reamed and re bushed.

Are there any other mods worth doing to ensure good manners and reliability? I think I have the stronger diff output shafts but will not know until the chap rebuilding the diff has cracked it open.

Are diff mounts and bushes worth upgrading and if so which are best?

Many thanks.

Jono

[paddy]

Popular opinion has it that standard diff mounts will fail pretty quickly after you've upgraded to CV joints, and this was my experience too. I replaced with TTR ones (also popular recommendation).

Paddy

[rgh0]

As you say you want to check your diff output shafts and if they are the early version with the reduce diameter shaft between the spline and the beaing mount or if they show any sign of twisting in the spline replace them.

The diff case itself is not important as long as it is in good condition. Fit the steel brace to the diff if you dont have it.

You have a Spyder chassis so it should be ok where the upper diff mounts bolt to the chassis. If you had a standard lotus chassis have a close look around where the diff mounts to the upper cross member for cracks. In a plus 2 it is worthwhile reinforcing this area with a plate clamped between the diff mount and the chassis and a large washer cut to clear the diff mount where it interferes under the head of the bolt on the top of the diff mount to help spread the load, even with donuts. Ideally the plate should be welded to the chassis but that is a body off job. Even with a spyder chassis put a shaped larger washer under the nuts locating the diff mount ot the chassis is worthile as the diff mount ears themselves can break

Ensure the diff torque rods mount bolts similarly have no cracks around the chassis and that the assembly with the rubber bushes leaves no free play anywhere either at the diff or the chassis. The torque rods should have a conical cut out in them and a conical nut and lock nut matched it to secure the toque rods to the chasiss without movement. This special nut is not listed in the parts manual or in the Dave Bean catalogue or refered to in the workshop manual though it is shown in the drawings and often this conical nut has been replace with a standard nut and the rods move around on the bolt hole resulting in chasiss cracks or the welded in bolt failing. The early Elan chassis did not have this arrangement and had a free bolt in a hole in the chassis rather than the later welded bolt and no conical depression in the torque rod but this would not apply to any of the plus 2 chassis I believe.

Assembling the rubber bushes on the torque rods is also debatable. The later parts manual shows just one cup wash and the rubber bushes bearing direct on the ears of the diff housing. The later S4 / sprint workshop manual refers to having 3 cup washers ( 4 if you include the fixed one on the torque rod with 2 between the rubber bushes and the diff housing ears.
Potentially the rods varied as well between these variations

cheers
Rohan

[gerrym]

Just to add to Rohans comments on the importance of correct hardware and mounting of the diff.

For the Spyder chassis, the torque rods are anchored to the chassis by bolts running through holes in the lower square section members. The holes in the chassis are bushed to prevent the tubes being crushed.

The bolt and nut is completely standard hardware. The important part is the conical washer which sits under the head of the bolt and mates with the conical depression in the torque rod. Check these have been correctly fitted, they are normally supplied with a new chassis by Spyder.

Regards

Gerry

[jono]

Many thanks for your comments guys. I have checked and have those conical washers which are mentioned.

I need to find a diff brace - perhaps one will turn up at Donnington?

I am alos at the dreaded budget creep stage adn think I may put a Quaife ATB diff in while I am at it

Jono

[gerrym]

Re ATB Diff:-

Go for it, otherwise you will pay the cost of rebulding twice over!

However, make sure all components are up for it. (output shafts, hub shafts, hubs, couplings, etc)

Regards
Gerry

[jono]

Hi Gerry,

My thoughts exactly!

However when you say, with regard to components, 'up for it' what do you mean. I have the non waisted diff output shafts and the outboard shafts look to be in good condition. Sue Miller driveshafts are being fitted.

Will the ATB diff put apprecaibly more strain on the driveline than a std open diff?

Are you suggesting that I should not fit an ATB diff unless I go for billet shafts al la TTR? (which my budget will not stretch to!).

Jono

[Foxie]

I am alos at the dreaded budget creep stage adn think I may put a Quaife ATB diff in while I am at it
Jono

I'm considering this, (when finances improve )

Is the Quaife ATB supplied as a kit, or all assembled in the standard casing ?

[memnon]

If you are doing that, just get the Tony Thompson hub shafts too

[rgh0]

The Quaife ATB diff centre comes complete. You just bolt it in to replace the existing open diff centre. However this does require that you dismantle and reassembly of the diff. I use a quaife diff in my Elan and it is great on the track especially accelerating out of corners. However I rarely if ever come across a situation on the road in the plus 2 where it would be needed. The wider track of the plus 2 unloads the inside rear much less in corners and you rarely push a car to the same absoluites limts in road use.

cheers
Rohan

[gerrym]

Jono, the open differential will always try and balance the torque,or less if there there is no traction on one side.

An ATB differential, depending on the exact bias ratio (fixed function of the tooth geometry), allows for torque transfer.

At the limit (gross simplification), for an Open diff, think of 1/2 the power going through one diff output shaft, rotoflex (or CVs etc), hardware, hubshaft, hub itself, peg drive, thin Lotus Steel wheels) as a maximum case. For a launch in first gear, the transmission provides a torque multiplication, the rubber tyre provides a torque reaction. For an ATB diff, depending on design ratio, the limiting case is all of the torque going through one diff output shaft etc.

So check that all loaded components are up for it.