3.9 diff question

[67-2door]

Hi all.
I'm sure it's probably been asked before but is a 3.9 diff a useful upgrade for a standard 1098 morris or will it struggle to pull it?
Thanks.
Neil.

[Monty-4]

I ran a 3.9 with a 1098 in kind-of-alright condition and it was fine, just a bit slower up hill! It's only an 8% change but takes the edge off the noise at higher speed.

[bmcecosse]

Yes - well worth doing -especially if you 'improve' the engine slightly with a larger 1.5" SU on a good alloy manifold and decent filter. Depends on the price of the final drive of course (the 'diff' remains the same) - some are taking the p*** now with prices, but it is 'money in the bank' - they won't go down in value!

[Monty-4]

The trick is finding one in good condition that doesn't whine at you during your journeys (insert jokes about other halves here).

[dalebrignall]

ive got one on mine you gain on crusing but loose going up hill

[bmcecosse]

But with that little bit of extra power I suggested above (a good 5 bhp) it will cope well with the hills.

[67-2door]

Well, I purchased the 3.9 diff this morning, not sure when I'll get around to fitting it (I'm in no rush). If it needs it I'll do a couple of the mods mentioned to make it breath a bit better.
Having said that, the man was also selling a 295 and a 940 cylinder head for not too much money .

[bmcecosse]

Well - you should have grabbed them - both!

[67-2door]

I might still go back and get one from him. Which is the better head to have, the 940? What's a reasonable price nowadays?

[olderisbetter]

I notice people using midgets diffs and half shafts, is it possible to change the whole axle to a midget one or is that not an easy thing, just asking as i have a 1500 midget complete axle i think it is a 3.9

[panky]

I believe the Midget axle is narrower so the half shafts are shorter and wont fit a Minor axle The diff is a straight swap though

[IslipMinor]

The 1500 Midget axle could have either a 3.9 or 3.7 diff in it, and the complete Sprite/Midget diff assembly is interchangeable with the Minor, BUT like the Minor, the later units have the filler in the axle case, and not in the diff nose. Most, if not all of the 3.9 are the later type, as are 3.7.

Sprite/Midget halfshafts of all years are shorter than the Minor and cannot be used (they are the same as the A30/A35/A40). The Minor shares its rear axle with the Wolesley 1500 and Riley 1.5.

[ManyMinors]

Most remaining Minor 1000 cars (all the 1098cc models) have the oil filler in the axle case. It is only the earlier 948cc cars which had the filler within the diff casing

[panky]

Yep, my 3.7 is from a Wolseley so no problem with the filler plug

[andypocock]

ive got one on mine you gain on crusing but loose going up hill

He's in Lincolnshire from the looks of it. Flat and windy from memory

[olderisbetter]

Thanks for some reason i thought the midget half shafts could be used, i guess the standard minor half shafts are strong enough for mild engine mods or do they have a habit of failing?

[panky]

At the most awkward of times

[bmcecosse]

Just don't do wheelspin starts....treat them carefully and they will be fine. The lower final drive ratio actually helps their longevity. Always handy to have a spare in the shed.

[bmcecosse]

Both heads are handy -the 940 obviously much better for air flow but you need to check exhaust valve clearance - looking for minimum 300 thou - if not you need to sink the exhaust valves into the head until there IS that 300 thou.And NO high lift cam !! A 295 is an easier fit - but if not already skimmed - it will need a good 60 thou off the face... They are 2.750 " thick when new. Don't pay more than £60 for either head - and only if they look 'ok'. Cracking between the seats on a 940 is always a possibility if the engine has been badly overheated/run dry of water.

[liammonty]

Don't pay more than £60 for either head - and only if they look 'ok'. Cracking between the seats on a 940 is always a possibility if the engine has been badly overheated/run dry of water.

I'm afraid 295 heads in good condition fetch a lot more than £60 these days - mine sold for over £200. It may well be worth paying more than £60 for, if it's what you want.