matt80
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| posted on 9/7/17 at 05:22 PM |
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Help for a new guy
Hi all. I posted on here last week (Advice please). I am looking to buy my first kit car. Looked at a locost with a 2ltr red top. He wanted 5k but we
settled at 4.5k. It seems to have a slight knocking noise when you come off the accelerator. Been told this is a worn bush on the diff. Does that
sound right? If so is it an easy fix and roughly how much? Thanks again everyone.
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r1_pete
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| posted on 9/7/17 at 06:32 PM |
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Some idea of what cars the various components are from would help.
Differentials usually run bearings not bushes, it depends which bearings are worn as to how much, a replacement used diff will almost certainly be
cheaper, unless you have the kit and skill to preload the bearings and set the backlash in the gears.
The noise could also be worn UJs in the prop, or several other components in the drive train.
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matt80
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| posted on 9/7/17 at 06:37 PM |
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Thanks for the reply. It's a sierra diff. I haven't bought it yet and probably won't til this is sorted
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Sam_68
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| posted on 9/7/17 at 07:44 PM |
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Very difficult to diagnose this sort of thing on the internet...
Is the knocking related to wheel rotation speed, or is it more random?
If more random, it could very well be a knackered bush allowing enough movement in the diff. for something to be contacting the chassis.
The other frequent culprit for this sort of noise is a worn UJ's in the propshaft.
If it sounds to be a regular knocking related to the wheel rotation speed, prime suspect would be driveshafts (CV joints probably), or very
worn propshaft UJ's.
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madteg
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| posted on 9/7/17 at 09:23 PM |
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I have spent 2 years trying to get rid of a knocking when coming off and back on the throttle. Fitted new gearbox,prop and had diff rebuild. It still
does it,
i have put it down to diff being solid mounted and no rubber shocker/doughnut on propshaft. You have to have a certain amount of backlash in
diff.
As above the doughnut/shocker stops the diff from knocking
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SCAR
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| posted on 9/7/17 at 09:50 PM |
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In your other posts you say it had the cam belt done less than 500 miles ago but bear in mind its only done 90 miles in the last 6 years so the cam
belt is now old.
Also you refer to the recorded mileage being low which is pretty irrelevant as the engine is from a different vehicle to the donor. If the current
seller bought this to fix it up and resell he should know what the knocking noise is.
I understand you wanting the car, they can be great fun and our heart can overrule our head but if your not mechanically adept be prepared for
potential heartache and expense.
Running a home built car is not like running a production car.
There is a good recent example on here where a guy wanted a v8 viento for well over a year. He contacted me several times to ask about buying mine,
eventually he found what appears to be a pretty good example on ebay. 3 weeks after buying it he's trying to sell it.
Try and be realistic with your expectations and understand what you are buying in to and you should enjoy owning a kit car
Good luck.
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jambojeef
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| posted on 10/7/17 at 11:11 AM |
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quote:
Originally posted by r1_pete
Some idea of what cars the various components are from would help.
Differentials usually run bearings not bushes, it depends which bearings are worn as to how much, a replacement used diff will almost certainly be
cheaper, unless you have the kit and skill to preload the bearings and set the backlash in the gears.
The noise could also be worn UJs in the prop, or several other components in the drive train.
Perfectly reasonable to suggest that the diff mountings, which are often bushed rather than solidly mounted, could be worn causing on/off throttle
knocking.
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