Rough patch

[Grant]

Hi, my P38 4.6 has a runs rough between 35-50ish, 3rd gear. Any ideas what i could look for here, desperately hoping its not a gearbox prob.

Cheers for any advice

[Range Rover Blues]

Propshaft balance possibly at that speed.

[Grant]

Hi,

To be more specific it accelerates smoothly until about 43mph it goes rough/slightly noisy, at about 48 it smooths out again.

Still think the propshaft could be at fault? I was thinking along the lines of it being a slight missfire.

Think i better get it hooked up to rovacom, reluctant to waste any more money on it but it'll be unsellable like this

Cheers

[Range Rover Blues]

Yes I do, also the rear rubber doughnut, and it's support bush.  It goes though the rough patch becasue it's resonating (like a tuning fork) at just the right speed.

Yes it can be a missfire, it can also be bearings supporting the CV, wheel bearings etc etc.  But start with the simple stuff.

Try driving it with first the front, then rear props removed (obvioulsy you have to refit the front) and check tham by hand for tight spots and play int he UJs, also look for evidence of grease exiting all 4 bearings of each UJ.

[Grant]

Thanks RRB

Come to think about it, i bolted a cheapo middle box from ebay on her a while back which ended up scraping on the propshaft.

We spent hours stripping down the brakes before we realised it was the exhaust causing the scraping noise! Perhaps its still haunting the car