NC2.0 Vibration / gearbox jumps when starting

Technical Area Engine, Transmission, Exhaust etc
1
  1. My model of MX-5 is: 2.0 Sport Tech 2013 Manual
  2. I’m based near: Glasgow
  3. I’m looking for technical help or recommendations on: After lowering the car and having full geometry done, I’ve gone out a good blast and bottomed out a couple of times, ripped one of the smaller under trays off and sheered a bolt head off one of the chassis braces.
    So had a fantastic day out, now I’ve got a very strange “kick” when starting the car and a vibration going on.

The kick is like the whole gearbox jumps on start up, clutch down or not depressed or in gear.

Out the car up on a ramp and had the car running. While it’s running I can feel the chassis after the engine mounts and it feels smooth. Touch the rubbers they vibrate, no visible signs of broken engine mounts. Shocks all look good, as do ARB etc.

Putting my hand on the offside upper wing when the car is idling , being revved I can feel a vibration.

Through the steering wheel driving I can feel a vibration.

Exhaust looks to be clear of body and mounts etc.
Thanks in advance.
I’m stumped…

Any clues?

2

Have you checked the diff casing for signs of road contact ?
PPF bolts tight ?
Maybe diff contact with road and PPF misalignment ?

3

You beat me to it :nerd_face: … also which undertray and which bolt sheered off may help diagnose the issue . The diff/ppf studs and nuts are pretty low hanging .

4

How much did you lower the car? I’ve recently fitted Meisters and accidentally got seriously low at the front and scrapped over speed bumps even at five MPH. You must have been tooling it to wipe out the stuff you did!. Sounds like extra enthusiasm. I like that😀

5

Diff hasn’t hit the ground, good idea thought!
Luckily / unluckily I’d had the car at Preserve and Protect, so it’s covered in Black Goo, aka Dinitrol. Which actually has an unintended consequence that impact point are reasonably easy to see.

PPF?

6

Haha!
It’s MeisterR Sportives and basically had them as low as I could without the wheels/tyres rubbing.

I also may have been driving enthusiastically within speed limits.

Thanks for the speed bumps reminder, the more I think about this, the more I think it’s been a combination of events.

There are very very large speed bumps all within the 1/2 mile approach and departure of my house.

I’ve been as careful as I can but the reality is this vibration could be from multiple low speed impacts and the enthusiastic drive.

I’ll get some impact photos up, when I get a chance to get under the car, when it’s up on a ramp.

Davie

7

Power plant Frame …it’s the girder type section that holds your diff assembly.

1 Like
8

Thanks you.