3.98 diff conversion possible?

[NDP]

Having a horrible job tracking down a 3.27 diff (at a reasonable price if it need rebuilding), so I was wondering if a 3.89 diff could be converted to 3.27 by exchanging the crown and pinion wheels? Something tells me this probably isn't possible otherwise more people would do it rather than search for a complete diff. 

Second part of my enquiry is: If adding a LSD unit into the diff, does it replace everything apart from the crown and pinion wheels?

[Pete Lewis]

3.27 and 3.89  have different  diff  carriers

Pete

[Nigel Clark]

The 3.27 crown wheel and pinion don't fit into the 3.89 carrier and casing. To change ratio you will need a complete 3.27 diff.

You could go far a Spit 1500 3.63 ratio to give slightly higher gearing. Blackline helical gear LSDs can be fitted to any of the small chassis final drive units, though extra machining is required for the 3.27 ratio. Paul Hughes at 2Spec Transmissions built one for my 2.5 litre GT6, it's excellent.

Nigel

PS: Simultaneous posting with Pete Lewis!

[NDP]

Cheers Pete. This confirms my fears that I have to go back to my search for a 3.27.

[chrishawley]

Worth a look at the following?

 

https://www.ebay.co.uk/itm/225139910849?hash=item346b6268c1:g:z5wAAOSwWEFirxjH&amdata=enc%3AAQAHAAAAoKKKFschttEQ8ZHQdX%2Boe%2Fyd%2B86cm54TxRQa24gZ1qK1MC3o%2FH5G84lMecK%2BYPeQ3E5RmtM7G7E08oev2rA0GCIyH595Hj2yiZLL4rkamv%2F%2BaI7hNNR33QLb7UwROfBchuo5Vzv91A7uUB5tMTovE%2FIGk6lRGepeyoxnOhlIsWVPVSIfcKAP8a5d5k%2FRjE%2FU8TswZUsnHdde3pNHH9OYEnU%3D|tkp%3ABk9SR5afysniYA

[NDP]

Nigel, thanks for the info and link to 2Spec.

[NDP]

Chris, yes I have seen it but lets be honest it needs a full referb and the price that is being asked is way too high to make it economically viable. For something in that condition I would only go up to £200.

[NDP]

I just know somebody somewhere will have one laid in the back of a shed / workshop and would rather get a couple of hundred for it in the knowledge that it is going to make an old Triumph back to its original spec again, than let it rust away where it is! Fingers crossed.

[johny]

Even secondhand unknown condition 3.63 diffs are getting to that money and 3.27 are much rarer (a lot more 1500 Spitfires produced than non OD GT6) so going to be difficult. Obviously when spending that kind of money you have the right to ask to see the internals either by photos or in person and thats the important part not the exterior...

[Nigel Clark]

The axles for Dolomite auto (I forget which engine size) also used the 3.27 ratio. The front casing/carrier from the Dolomite auto axle can be mated to a small chassis rear casing.... Gives another possible source to find a 3.27 diff, though they are all getting rare now.

Nigel

[johny]

Youre right although the Dolomite front casing is no use as it doesnt have the holes to bolt the front cross support plate required for the small chassis models. So you would have the crownwheel + carrier and pinnion but it sounds like still need a complete 3.27 casing☹️

[Peter Truman]

If I remember correctly a fellow club member here in OZ wanted a 3.27 diff in his GT6 for freeway driving he found the correct crown wheel & pinion but needed a new diff case as he wanted to keep the 3.63 diff too. He was searching for a std Herald 4.1 case acknowledging he would have to modify the inside of the case by grinding it out to clear the larger crown wheel. Not sure if he ever achieved or completed the mod or if it worked! 

Interestingly there was a supposed NOS 3.27 GT6 diff on Gumtree here a couple of years ago for sale locally in Melbourne but he wanted over $2k for it, a very rare beast here as all GT6's were personnel imports!

[Pete Lewis]

they have different diff case carriers to compensate for the thickness of crown wheel ( diff case= the bit with the CW attached and house the differential gears )

offten called bevel gear carrier  and many more   not the axle case 

a 3,27 has bigger pinion diameter so has to be thinner than a 3.89  its this offset that makes them non interchangeable 

Pete

[NDP]

Thank you all for your input. If anyone comes across a lead that may uncover a 3.27 I would appreciate a heads up.

Once again, thanks to all.

 

[NDP]

Thread closed, I have now found one, thanks to Dick Twitchen.