Diff oil leaking from a Ford diff

[Steve-T]

I've recently changed over the 4.2:1 LSD on my kit car to a 3.54:1 diff. The axle is a MK 1 escort.

The oil has leaked out of the coupling from the diff to the prop shaft.

When changing over the diff, the mechanic had to swap over the 'flange' from the 4.2 to the 3.54, so that it it would fit the prop shaft coupling.

The question is, does the diff 'flange' need to be have a specialist fitment onto the diff spline......the reason I ask is that the when I said "well if I don't like it, we can always refit the old diff..." He said " it will need a specialist engineering fitment for the 'flange' because it needs to be fitted under pressure.

The hind-sight question to that is.....does this one we're fitting now also need the specialist fitment....I guess the answer was yes.

I've attached a couple of pictures to show the diff in situ :-





I will be having the current diff removed, mainly to check it.

Many thanks for any advice given,

Steve

Edited by Steve-T on Sunday 15th April 12:28

[grahambell]

Not done much with diffs, but from memory, on the 'English' axle where the diff is in a housing that bolts to the front of the axle, there's some sort of compression ring that the drive flange tightens down on. Think there's a set amount you're supposed to 'squash' this when assembling the diff unit, which could be what your man means.

Haynes manual for Anglia/Mk1 or 2 Escort/Mk1 or 2 Cortina/Mk1 Capri would tell you as they all used that type of axle.

[that daddy]

Some have the collapsible spacer some dont they have a fixed length sleeve(Ford chopped and changed at random),it adjusts the bearing preload get it wrong and you will have pinion bearing failure soon after,if the oil is leaking down the splines of the pinion shaft beetween the teeth of the flange you need to remove the nut(marking its position & turns off)degrease the splines on the shaft & flange then smear with some silicone sealant refit flange and nut and tighten to original position and turns but nip up an extra 15 degrees approx(this part is most important).I had the same problem on above axle running 3.7 gears,i thought it was the front seal(it was not)then realised the oil was seeping past the splines,the strange thing was this axle had not had bits swapped around there was no mention of doing this sealing on a rebuild, even with the factory Ford workshop manual,hope this is useful

[Steve-T]

Gents, thanks for your replies. My plan is to take off the diff and swap it back with the 4.2:1 which was originally fitted. This will give me the opportunity to check the condition of the 3.54:1 fitted.

I changed the diff over because the car was pulling about 8000rpm at 70mph. Changing the diff didn't make a vast amount of difference. I understand that fitting 14" or 15" rims and appropriate tyres should drop the revs and give a greater top end. Apparently it currently about 105mph.

The car is up for sale, due to my bad back not being compatible with the driving position :-
www.pistonheads.com/sales/155557.htm

I very keen to sell it as A1, so the option of re-filling the diff with oil and moving it on to some poor unsuspecting punter is not one that I would take.

I'm going to source another correct sized flange and have it pre fitted to the 4.2:1 diff. (The one that came with the 3.54 was too big for the drive shaft, so we had to swap over the existing flange...that's probably where the problem was created...)

I'll then take it back to my man and we'll swap the diffs, safe in the knowledge that it won't leak again.

To be fair, fitting the 3.54:1 diff did take a bit of the sparkle from the car.

Many thanks,

Steve.

Edited by Steve-T on Sunday 15th April 10:46