Hey chaps

I have a 2wd cossie 1990. when i bought the car i had a lot of transmission vibrations. I have been working on trying to make it a smooth car to drive.
Have had a new clutch assem, balanced the flywheel. taken the rear axles off re greased the cv joints and had the drive shaft checked for uj's and balance.
Its getting better but still has a annoying vibration at approx 3000rpm. sounds like the whole back end of the car is vibrating at this rpm. happens on acceleration and deceleration... to the point i feel like selling it and starting again. I am sure the diff is quite worn cause there is quite alot of slop when accelerating and then quickly lifting off. so im going to try another diff, problem is there arent any over here! so can anyone tell me if i get a xr4i or xr4x4 diff head and axles (bit more common) will they fit into the back of this car? what is interchangable with these sierras. tried buying a saphire 2.0 twin cam diff which would fit but the flanges are alot smaller than what is on my axles. then thort i could just use the cossie stud axles but ones longer than the other. ahh dam cars. comments would be cool

 

have you changed the bush that holds the diff?

 

Yeh mate that was the first thing i tried. cheers though. it just feels more mechanical than a bush though if that makes any sense!! to the point when it gets into its vibrate mode the gear shifter if vibrating to when you hold if ya can feel if shakin pretty much the whole drive line

 

Could be a tooth of the rear diff? Happened to mine when it lifted a rear wheel when I was on full song in 4th lol. Could also be a problem with your prop being unbalanced?

 

2WD Cosworth diffs, are completely different to lesser models, also as you found out, as is the rear beam. Lesser models were 7" diffs, 2WD Cosworth are 7.5".

The rear suspension setup on any model derived from the Granada, but I believe these have have 7.5" diffs (Probably the same diff, if so one of these would work?).

Also all Cosworth varients have a LSD, most other models don't, so you don't want to be fitting the diff you have!

As said though ultimatly it's bushes that let these down due to age (What else can you expect from perished old rubber)

A poly diff mount for £100 is a good investment, and maybe check the condition of the beam bushes, in particular the beam mount bushes.

Martin

 

Check the prop support bushing too, mine was badly worn and gave very similar symptons to yours.

 

thanks for the thoughts peops, i have had the drive shaft checked and balanced the centre support was within specs. i did send the diff to a local company who told me he could tighten (shim) the lsd but when i got it back it was the same, just left me $250 lighter, wanker. i did notice the spider gears were prity worn so the comment on the chiped or broken tooth may be a good point. have found someone local with a 4x4 v6 car that he has wreaked so am going to try his diff. one thing i did notice is the lsd basically doesnt work and when i use to much power and it spins one wheel (quite often!!) it makes pretty nasty noises. il let ya know how i get on

 

got same problem with mine,if you boot the car the rumbling is terrible but once up to speed and cruising its fine or driving very carefully it seems ok

 

so im not the only one!! your car sounds the same, its weird if you use real light throttle you can hardly pick it. as it goes up through the rev range you can feel the different spots of smooth and vibration through the gear shifter, but its at its worst at bout 3k, with accel and deaccel. will try this other diff and let ya know how i get on...