Hi everyone! I bought my Locost 7 with a Pinto engine and Type 9 'box a few weeks ago and love it to bits! I knew I would never have the time to build one from scratch so I did the next best thing and bought an example that needs some work. It is MOT'd and has today coped with me and a friend hammering the nuts of it all day round Abingdon Airfield! The plan is to rebuild her bit by bit so I can still enjoy driving her while I work through the rebuild and will end with a new more powerful engine (yet to decide which one).

The only problem I had today is that as I was changing up or down in anger the rear of the car would lurch to the right as the clutch engaged. The rear suspension is independent and I noticed that one side seemed softer than the other. I adjusted them to be even and it helped a little but not enough for me to think this has solved the problem.

I had her on the ramp the other day and thought that the gearbox mounting rubber seemed to be very soft and is starting to perish. Didn't have time to order one before Track Day though.

I would appreciate opinion on whether a dodgy gearbox mounting would cause the issue outlined above.

Thanks in anticipation of any replies...

a bit more info on the car would be good, what axle does it have diff etc. The type 9 mounts are a touch soft so wouldnt think this was your problem. are you used to driving RWD as this is a totally different feel than FWD. The feeling you may have is similar to what a FWD drive does without and LSD the car will pull you one way RWD pushes

Hi. Yep I have always only driven RWD cars and my daily drive is a RWD 4.0L V8 so I know the 7 doesn't feel right. The rear drive comes from a Sierra diff connected to the hubs with driveshafts (not live axle), and suspension is Avo adjustable for height and damping. She is not particularly fast as she only has the 1.8 Pinto with twin carbs. With another 20bhp she would be undrivable in her current condition in my opinion as the car would just spin out as soon as you change up under hard acceleration, or change down when lifting off however careful you were. It feels like someone heavy is jumping on the offside rear corner of the car and making her pivot as soon as I lift the clutch. As you say it is very similar to torque steer on a FWD (but from the rear), but it is very severe. I could understand it if the car was pushing out a couple of hundred BHP, but she probably doesn't have 100!

I am pretty sure the problems are one, some or all of the following but just wondered if anyone had any other opinions...

1, Gearbox shifting as mounting too soft
2, Knackered rear offside shock
3, Rear camber problems
4, Worn rear bushes

Has anyone else had a similar symptom and what was the cause/cure?

[Edited on 15/4/11 by david_hornet27]

[Edited on 15/4/11 by david_hornet27]

I can't see how soft gearbox mounts would have any bearing on the rear end handling as the diff is fixed to the chassis so. Besides the mounting is always soft even on the larger v6 fords with type 9's. Sounds like either you have a troublesome limited slip diff or a suspension joint is worn

That too me sounds very much like a knackered diff. The effect being that you only have 1 wheel drive so all the power going to one rear wheel is causing it to lurch that way or engine brake only on one side when you lift off the power. When my E30 BMW's diff let go (on numerous occasions) it always felt just like you have described.

diff or rear wishbone/hub bush/mounts

needs identiyfing before you drive it much further

I agree with either uneven power deliver from a differential or worn bushings on the suspension. How were your rear brakes? Don't suppose one is binding when its gets hot is it?

Thanks for all the help guys! I had the Formula Ford guys look round her yesterday and they were convinced it was engine or gearbox mounts. Engine mounts are fine and I wasn't convinced about it being the gearbox mount which is why I thought I'd ask here. Knackered diff seems much more likely and I hadn't really thought of that as I was under the impression that they either worked or they didn't.

To continue...

I had a good look under the car today and this is what I found! Scarily the weld had failed on the bracket holding the bush for the offside lower rear suspension arm, the inner front bracket ...













I have obviously had a GOOD look to make sure there are no more problems or likely failures and I am confident this is the one dodgy weld on the car. One too many I know! I understand that the welds are obviously under load, especially in this area, but has anybody else experienced anything similar because I was shocked at what I found? I will be checking regularly now for similar problems...

I was hoping I could get some opinions on how best to repair this. I am not a welder and will be calling someone competent in to sort it for me. What worries me about the repair is the hole left by the bracket coming off! Should I be looking to cut a hole in the chassis and welding another square piece in its place, or do you think it would be better to patch just the hole and refit the bracket to the repair? I am looking for the safest option.

This is how i would do it
Cut the small part of box out from the bulk head to the weld/ joint then weld a new piece of box in / re-weld the bracket on + weld it to the diff mounting plate
Jacko

Thanks Jacko I was thinking along the same lines so it's nice to have it confirmed. Just got to find a piece of box now, and a welder.