My car has started to make a clonking noise when I open or close the throttle quickly. If I roll on the power it is fine. Actually, I can't so much hear it as feel it.

I quickly lifted the bonnet last night and turned the prop by hand from the engine end. The box was in neutral. There seemed to be 5-10 degrees of backlash in the prop.

What are the potential problems, other than diff backlash and a loose prop?

Is it going to be a big problem or should I not worry.

For info, I have a sierra LSD and an R1 engine with a two-piece prop and no reverse box.

A couple of things worth checking if you havent already.

Diff to chassis bolts loose

Lobro joint bolts

regards
agriv8

I'm having the same problem since fitting my new engine. Chatting to a mate, he suggested the much sharper throttle response of the new engine might be a contributing factor, sao i'm going to try fitting a heavyish spring to the throttle pedal to see if it damps it a bit. Its always clunked, but it seems to be getting worse. prop bolts etc are all tight......

I'd say the prop uj's the most likely culprits - the bearings could have gone

worth checking anyway

If it is the prop uj's they are easy fixed if you can get the propshaft off the car

[Edited on 5/9/06 by mcerd1]

I have the same driveline (apart from a ZX9) and mine does the same.
I'm sure someone brought this up on the forum before...and from what I can remember about reading the discussion, it didn't unduly concern me so it must have been OK
fingers in ears..... lalalalala

Sounds like it might be prop.u/j's. DO NOT ignore these if this is the case, a flailing prop in a car like this could be very unpleasant!
Phil

Mine's definitely not the prop as the backlash is apparent at both the diff input and the sprocket adaptor in the same amount. The prop is only 20 miles old too.
I've found the thread I originally read at
link to thread

Sorry for appearing so blase about it

Mine does this on part throttle and when you lift off. Ive checked the prop as best as I can and it just seems to be the backlash in the diff and gearbox. It also isn't helped by having everything solid mounted and right next to you. Every little thing feels much bigger when it's bolted next to your kness!

TRT prop will go a long way to curing your problem

Phil

Helfire, what is a TRT prop like and who sells them, also how much is one?

Cheers

matt

Torque Resilient Tube. Basically, it's a tube within a tube and the two bonded together with rubber. Dunning & Fairbank modified our MK propshaft for about £125 IIRC which involved replacing the rear section with TRT, fully balanced and even painted

Hang on while I go get a link for Dunning & Fairbank........................

Here you go - Link





[Edited on 5-9-06 by Hellfire]

So the most likely thing is diff backlash. I'll check next time I'm in the garrage. Will this problem only get worse? Will the diff brake? Is the backlash caused by knackering the teeth on the crownwheel and pinion or by backing the pinion out a bit?

I can see how a TRT might slow the problem but I guess that it won't cure it. Am I right?

My guess is that it's just normal diff backlash. Once you get used to driving a car and become more comfortable with it, you pick up on noises that have always been there - you've just not really noticed them before. I would also imagine that it's quite difficult to break a diff in a seven style car under normal use, given the weight of the car that it originally had to propel.

You're right though, it won't cure the problem with the driveline clonking, it'll just be far less noticeable and not so harsh a take up on your gearbox, which can be beneficial for engine longevity.

Phil

Thanks Phil, that's rassuring.