Diff central.

[Staghound]

Having replaced the diff on its bracket and fixed it to the shell,the front(where it fixes to prop) is not central.The diff shape and the differing length of the extension piece brackets suggest it won't be,so the question is.....is the gearbox off centre when installed,is the offset corrected by the prop or have I done something wrong already?

Thanks Andrew.

[Rubce]

Hi Andrew

The brackets on one side of the extension piece are longer than the other. Looking at photos in the book I did of my car's restoration the propshaft is positioned towards the driver side of the transmission tunnel. So yes the input flange of the diff will not be perfectly central but positioned towards the drivers side.

Regards

Bruce

[dasadrew]

A picture paints a thousand words (as Telly Savalas sung!)

Lubrication Chart.jpg

[jleyton]

A picture paints a thousand words (as Telly Savalas sung!)

Well, 57 anyway !

Cheers

Julian

[dasadrew]

Well, 57 anyway !

Cheers

Julian

Can't sleep Julian??

-20.5°C outside here now - hope the daily will start!

[jleyton]

I've always been an early starter (even if I do come out with c**p, like the above, first thing in the morning ) and that's especially useful now that we've got a log burner powering our central heating Luckily, we're a lot warmer than you right now. Good luck with your daily !

Cheers

Julian

[73stagman]

There is a reason for this! It is so that the propshaft universal joints get proper movement to move grease around inside the cups in the uj joints. Thats what I got told when doing my apprenticeship thirty years ago.... maybe it was a wind up I dont know. Every prop shaft siince then I have seen does not run centre to centre! There is always an angle some where between the output of the gearbox and the input of the diff. Either in the vertical plane or the horizontal plane sometimes (ie Stag, big trucks etc... it is in both.
There was a maximum and a minimum design angle specified by the design team when I was building Herclules cargo loading trucks we had to adjust the central holding brackets to be within these angles.

[wilf]

You are correct Neil - UJs need some misalignment to work properly.

[V Mad]

.......and did they tell you the angles at each end have to be equal to avoid vibration?

[73stagman]

.......and did they tell you the angles at each end have to be equal to avoid vibration?

The drive shafts we were fitting were rev limited because the angles and "raise and lower" capabilities of the trucks ensured vibration was inevitable. In fact one tester ignored all the warnings and drove one of the trucks beyond its capabilities and the drive shaft removed itself from underneath the truck and was thrown across a kids playing field like a javelin including the final "point in the ground"

[73stagman]

I should add that on all future builds the truck engines and gearboxes were rev and road speed limited to prevent repeat occurrences.! And also that no one was injured during the "R & D test case" but the diff and gearbox were written off!

[alan_thomas]

surely the simplest reason why the prop is offset is because the crownwheel is to one side of the input shaft which means, if you want to keep the drive shafts the same length the input shaft is offset.
I cannot believe the triumph engineers thought of 'UJ' wear.
-Alan

[73stagman]

If it was not for practical engineering reasons then it would be simple enough to cast a symmetrical diff housing and position the crown wheel and carrier in such a way as to align the centre of the input shaft with the centre of the diff thus eliminating the "off set" all together.

Triumph designers didnt design a differential they just adapted a well proven drive system to fit the Stag / Triumph 2000 and other similar cars. The offset requirement is a fundamental requirement of a differential because of the UJ's requirements for lubrication. The offset is in place to ensure the angles exist in all applications. It just so happens that in the Stag there are angles in the vertical plane too. In the case of the Spitfire the angles in the vertical plane are negligible and so an off set to one side is essential.

Just saying..........

[Staghound]

Well I've learnt something here today.....so the prop must be offset with equal angles front and back,thanks for the info chaps.

Many thanks,Andrew.