Propshaft alignment question ?

[Mark]

I started mocking up my 302 in my Sierra and could do with advice on how critical prop alignment is.

It's probably going to have to be a 2WD cossie prop with the front end shortened and a T56 front spline as I think it's a bit too long for a one piece.

Does the prop have to have a dead straight run from the back of the box to the diff ?

The problem is at the moment I have nothing to fit to try and guage it as the T56 prop that came with the box is too short and the cossie prop is too long

Thanks for any help

Mark

[sidecar]

You don't want the propshaft alined, this is really bad for the UJ bearings, you want a small angle at the diff joint, and the same angle but in the opposite direction at the gearbox joint. Basically the setup should look like a very stretched out "Z" either looking from the side or looking from above.

[kiwicar]

Aim for 3 to 7 degrees flex at each end if you can and as said try to have the same at each end, but you don't have to be too fussy, a degree or two different at each end is fine as long as they arn't straight.
Best regards
Mike

[Mark]

Thanks for the info chaps

Mark

[Ian Anderson]

And the UJ's out of phase or you'll get bibrations

Ian

[Mark]

Thanks again,
It looks like my engine will be tilting back between 2 and 3 degrees and the diff points up at between 1 and 2 degrees.

So in theory I have between 3 and 5 degrees difference.

Engine mounts are turning out to be a pain in the bum

Mark

[ChrisJC]

If all else fails, you can get CV joints in the propshaft. They were used on the Rover SD1.
When I had the prop made for my van, I used Bailey Morris (in St. Neots), and they had brand new CV joints (SD1) in stock!

Chris.

[Mark]

I am a bit concerned at the amount of revs that it might do.

With a 0.62:1 top gear, the prop could in theory IF I had enough power be turning at 9700 rpm if the engine hits 6000 rpm

The front part of the two piece prop is going to be fairly short compared to the original cossie one, would this cause problems ?

thanks
Mark

[ged]

Don't you mean 3720 RPM.
Oops!! Got home totally knackered last night & got everything back to front.

[Mark]

Don't you mean 3720 RPM.

0.62 engine revs = 1 propshaft rev

So in 6000 divided by 0.62 = 9677 rpm

I doubt it will have the power to pull 6000 in top but 5500 is a possibility.

Mark

[kiwicar]

Hi
If it is ballanced properly it will be fine, scary thought though! personally if it were me I would put a loop around it (or maybe 2). think of the ones on NASCAR oval tracks they spin at those sorts of revs for 500 miles at a time
Mike

[DEVONMAN]

[0.62 engine revs = 1 propshaft rev

So in 6000 divided by 0.62 = 9677 rpm

I doubt it will have the power to pull 6000 in top but 5500 is a possibility.

Mark[/quote]

On the sierra there is a centre support to the prop. If you have changed the position of the engine then you may have to adjust the centre support to get proper alignment of the prop. On my sierra project (4.6 RV8) I got clutch judder until I lowered the centre support with some spacers and longer bolts. Ford say that the two sections of the prop should be straight in line with each other and as standard some spacers are fitted to some cars.
Regards Denis

[Mark]

I remember having the same problem when I did a Rover V8 Sierra, I also has to mess around with spacers to get the two halfs aligned.

cheers

Mark

[Ian Anderson]

Vibration is probably from the UJ's not being out of sync

Ian

[DEVONMAN]

Vibration is probably from the UJ's not being out of sync

Ian

What vibration? The Sierra prop has 3 uj's so keeping the 2 sections in a true line eliminates the effects of the middle uj.
regards Denis