hi i have recently converted my 120y to manual i couldnt get a driveshaft for a borgwarner diff so i got a h165 driveshaft and put on the borgwarner flange for the diff.

the whole thing is a bit small but the yoke enters the gearbox more than halfway so i thought it shuld do for know. the only problem is at 80km i get a slight vibration from the car, nothing specific shakes just sort of the rear of the car moving forwards. it deacreses at 100km/h

if you change the yolk from a different driveshaft do you have to get it rebalanced?

Thanks!

typically no but it may be the shaft wasnt balanced before. i wouldnt think the uni joint sizes would be the same.
that may be the issue.

take it to a tailshaft shop get it done right imho.

yes, you should

put new uni's in?

thier the same size and yes new uni at the back only not the front yoke.

They might take a different size circlip, which would not center the J-joint. causing vibration.

I wouldn't change the front u-joint unless it is bad, and you can easily and accurately test it by hand. Remove the Propeller Shaft from the diff and flex the u-joints by hand. It should move smoothly (not stiff), in all directions and be tight and smooth. Replace if loose or binding or notchy feeling.