Diff Hitting Chassis

[aussieelan]

Recently rebuild the diff in my +2 ... new crown wheel, pinion bearings etc. All went well. The car always had a driveline clunk, which I assumed was caused by diff internals.

On removing the unit I noticed the housing was worn at the top were it had been hitting the chassis (image below). When I re-installed, I added a couple of extra washers (diff brace, big washer and added 2 x 2mm washers) to try and drop in down a bit further to remedy this. I also had to trim back the torque rob bushes to swing the diff forward to try and get clearance between the diff and the chassis. I managed to get a mm or 2 clearance, but no where near enough. I still have a driveline clunk and lots of noise as the diff is basically in contact with the chassis when driven.

All this seemed a bit odd, so I went looking for reasons why. First assumptions were top diff mounts, and as I had to remove the fuel tank for another project, I decided to move this project up and do it now.

Not having much experience with older Elans chassis (my knowledge base is M100's) I did some searching for pics, and after finding a few chassis images of the area, It appears that a previous owner had modified the "diff housing cage" on the chassis and re-inforced it with a plate (as pictured below). The job was so well done, it had never occured to me that it was non-factory.

So ...

Is this a modification? .. or is it as it should be?
If it is a mod, I need to undo it.

Options would seem to be either

a) drop the diff in the car and move it forward, cut out some more bodywork inside the boot and "modify" with an angle grinder to get some clearance.

b) remove the diff totally and do the re-mod from under the car

c) body off and chassis mod (~shudder~)

d) something else

If its not a modification, then I need to start looking for why I have so little clearance in this area.

Appreciate any feedback or ideas.

Andrew

[Old English White]

... A baby Elan chassis !?!
More seriously , what about gearbox & main shaft ?
Does a "big flange" at the place of a "small flange"diff be the reason ... ?
Andrew , one of us will soon give you a clue to the solution ...
Christian.

[rgh0]

Hi Andrew
I have never seen a reinforcing plate like that on a standard Lotus chassis or the Spyder replacements so I dont think its orginal. However it does look very well done with the formed hole flanges.

I would not try to move the diff to far out of its orginal position, I think its better to remove or alter the added reinforcing plate to get enough diff clearance.

The contact area is relatively small and the diff must only be just touch so you can perhaps "panel beat" the reinforcing plate a little to provide more clearance. You would need to be careful you dont bend the rest of the chassis when you do it.

You could try and cut the plate out entirely or at least cut a hole where the diff hits with a grinder with the body still on. Be careful you dont cut or nick the top cross member or the 2 tubular braces that run back to the chassis bottom plate behind the diff. Also be careful that none of the grinding sparks lodge against the fibreglass somewhere and potentially sit there until it catches fire.

From the photos it looks like its the flange around one of the holes in the reinforcing plate that is hitting the diff - you may only need to flatten or grind off that flange to get the clearance you need.

If all that is to hard to get access to do then its probably body off time to get access needed.

cheers
Rohan

[tcsoar]

Hi Andrew,

That plate looks suspiciously like the side panel from a spyder chassis, the formed holes were what caught my eye. I agree with Rohan that it does appear to be well done, but why I do not know why, and I would not move the diff any further than you already have. Personally I would take out the diff and try to remove the lip from the holes, otherwise it would be removing the body to rectify.

Chris.

[robcall]

Spyder chassis from the rear.I am assuming the vertical tubing behind the diff has been plated.

[CBUEB1771]

I have attached a photo of a new Lotus replacement chassis I recently bought for my +2. As with the other folks replying, I have never heard of an Elan or +2 being reinforced behind the final drive. And thanks to Gary Anderson and the ever-vigilant Beau for getting the chassis to my house in his pickup truck.

[aussieelan]

After much cursing and scuffing of knuckles ... trial fitting and trial re-fitting of diffs ... panel beating and more cursing .. trying different sized washers/combination of washers, I was about to give up ... ... when the replacement diff mounts I had ordered arrived.

OMG, they are totally different from the old ones, and once installed everything else just kinda fitted!

I also took the opportunity to seal the inside of the fuel tank and fix some small electrical gremlins. This afternoon the +2 ran and drove for the first time in a couple of months ... with a nice quiet diff with no driveline clunks

All I have to do now is finish fixing the (no such things as a) small electrical gremlin, the squeaky front suspension bushes, a couple of minor oil leaks, throttle return springs, hesitation in the acceleration curve........ mmmmmm

More garage time needed, but atleast it runs.