Same prop shaft for 3.27 and 3.89 differentials in a GT6 MKIII?

[NDP]

Hello,

 

I have a 1972 Triumph GT6 MKIII non-overdrive.

Prior to my ownership someone has exchanged the 3.27 diff for a 3.89 one. I am in the process of trying to change it back. I have removed the prop shaft and sent it for reconditioning but then I have had a worrying thought. Presuming that both diff's were original Triumph diffs (and not altered in any way from the original specification) would the prop shaft be the same for both differentials?. The gearbox has not been changed and remains a non-overdrive box with original specification.

 

I would also be interested in hearing from anyone who has a 3.27 diff for sale.

 

Cheers,

 

Neil.

[NonMember]

The diffs are externally indistinguishable and the propshaft is thus the same. The propshaft for an overdrive gearbox is shorter.

[NDP]

Thanks Rob, that is a relief. All I need now is to trasck down a 3.27 diff!

 

Cheers,

 

Neil.

[johny]

Hmmm thats probably not going to be easy as the number of non OD GT6 produced was pretty low and their diffs very sought after so that makes the chances of finding one thats good and at a reasonable price very unlikely. Much easier would be to fit a 3.63 unit from a 1500 Spitfire which wont give as much of a drop in revs but still a worthwhile improvement....

[Nigel Clark]

Yes,  same prop.  I switched from 3.89 to 3.27 and never changed the prop. Just swap the diffs over... nothing else needs changing except for speedo recalibration. 

Nigel

[chrishawley]

3.27s are indeed rather scarce.

Poss worth a look at

https://www.ebay.co.uk/itm/225080199537?_trkparms=amclksrc%3DITM%26aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160811114145%26meid%3D77b648b22740446690b67422c79c730f%26pid%3D100667%26rk%3D2%26rkt%3D8%26sd%3D195231247885%26itm%3D225080199537%26pmt%3D0%26noa%3D1%26pg%3D2334524%26brand%3DTriumph&_trksid=p2334524.c100667.m2042

[johny]

For the money youre going to have to pay I would want the diff opened to inspect and count the teeth (confirms ratio) as although the bearings can be replaced the crown and pinion shouldnt show signs of wear.....

[Colin Lindsay]

I suppose it's a risk you take with all unknown purchases but the description on that one is a bit of a get-out clause; 

"Smooth with little backlash, this has been in long term storage by the previous owner as a known good diff. I've not heard this on the road so I can't guarantee it but it was obviously kept for a reason."

It's a high price for an unknown; you buy it, it's duff, but it's not the seller's fault. He seems to be a kind of Triumph dismantler, though, going by the numerous other items for sale.I wonder, as it's cash on collection, is it possible to go inspect the item, prior to bidding? 

[johny]

yes sometimes they offer refunds but postage is at your cost and of course youve got to install it in the car to find out if it whines....

[Clive]

I have managed to break 3 x 3.27 diffs, and I had bought a few which were missing teeth too. 

You may be better off tracking down an axle from a dolomite 1850 auto, and getting the internals swapped with yours. 

How I wish I had kept the 3 good 3.27s I sold about 8 years ago, people shied away at the spares day because I had teh rear case off to show the condition. But I did it for a  reason.

[dougbgt6]

3 hours ago, chrishawley said:

3.27s are indeed rather scarce.

I'm not telling where I live or where my car's parked. 

Doug

[johny]

Might be best to put the money towards OD although that comes with its own risks. However once up and running satisfactorily the cost is most likely to have been added to the value of the GT6👍

[Pete Lewis]

TD Fitchetts ad in the courier shows as 460 recon  600 new CWP 

there is at least some consumer rights with a proper retail sale 

bear in mind recons are exchange and should be like for like or you may loose any surcharge 

Pete

[dougbgt6]

2 hours ago, johny said:

Might be best to put the money towards OD

Oh, I shouldn't have looked 

Triumph Spitfire 1500 GT6 Dolomite 1850 Gearbox/Overdrive Unit | eBay

Doug

[Colin Lindsay]

Same seller as the differential; that was listed before then ended early as 'no longer available' but back again now.

I think late versions require a different clutch to the early 3-rail versions? 23 vs 10 splines?

[johny]

Make me laugh these ads where it says an item has been overhauled etc etc. Its a secondhand gearbox with unknown history the same as any other unless you have verifiable paperwork with bills and serial numbers! It works though as people will pay more for it because they WANT it all to be true....

[NonMember]

59 minutes ago, Colin Lindsay said:

I think late versions require a different clutch to the early 3-rail versions? 23 vs 10 splines?

Yes, plus if it's a later Dolomite one then it doesn't mate to the clutch housing without mods. Assuming it is a Dolomite 1850 box, not one of the other types the seller thinks it might be.

[johny]

Serial number starts WM so should be 1850 and yes needs mods including catering for it being an inch longer than a 3 rail equivalent....

[NDP]

Gents,  thank you for all the information / suggestions.

I have had my gearbox refurbished so am reluctant to now exchange that out for an OD unit (plus the car didn't originally have one).

The thing that worries me is all the talk of 3.27 diffs failing. I would hate to spend a bucket full of money and then discover that it failed. However, I would be surprised if it did fail because I don't exactly thrash the car when driving it and I never take it to track meetings etc. Is there some inbuilt known faults with the 3.27 that cause it to fail with normal use? If I bought one that needed refurbishing what are the views of having a LSD incorporated into it? (MLR or Quaife). Would this cure any weak points in the diff?

Cheers, Neil.

[Clive]

I broke the 3.27's with a heavy right foot and a 2.5 engine. In a 2 litre GT6 it won't be such an issue, much less so if you are not heavy footed.

However, using an LSD will "fix" the wekness of the 3.27. Don't expct it to be cheap though. 

[Pete Lewis]

with a higher ratio diff you have to transmit more torque for the same performance  as the pinion diameter gets larger and the crown wheel may get thinner 

(i dont recall if triumph changed the crownwheel thickness or made a alternative diff case to accomodate the offset )

so it is close to the torque limit before something decides to go Bang compared to 3.63 or 3.89  :1 diffs  

Pete

 

[Ian Foster]

Neil

My Mk2 also came out of the factory as non O/D with a 3.27 diff.

I swopped out the ageing gearbox for an O/D unit from a Vitesse, (in the days when such things could be harvested from the local scrappy), subsequently briefly tried a 3.63 recon diff but actually reverted back to a 3.27, which probably did circa 80k miles.

This was again swopped for a Canley recon 3.27 unit when (actually soon after) we rebuilt the car in 2011 and it has done 15k miles since.

I understand that 3.27 units were originally built with Gleeson gear sets which required a specific carrier and I believe this is the weak part of the original axle.

Dave Pearson at Canley's explained that they now use 'Orlicon' pattern sets from Turkey, which do not require the original 3.27 carrier.

LSD conversions are available from 2spec Transmissions. See attached research document.

With the 3.27 diff, in top gear 70mph = 3400rprm and with a 25% D or J type O/D this reduces to 2800rpm.

Ian

 

GT6 LSD.pdf

[Steve P]

As Clive said, unless you do "No 11 starts" leaving car shows as some of the Ford boys do, a 3:27 will be fine. I have had one in my tuned 2.5 Vitesse for 10 years putting around 170BHP through it. I have a saloon gearbox as well, Ian`s speed and rev figures above are similar to mine. I have a Blackline ATB on the shelf but i havn`t got around to getting someone to build it but i have good things about 2Spec.

Steve

 

 

[Nigel Clark]

I have a Blackline limited slip diff with 3.27 ratio in my 2.5 litre GT6, built by Paul at 2Spec. I'm delighted with it. 

Nigel