Jump to content

GT6 3.27 Diff Wanted


Nigel Clark
 Share

Recommended Posts

Hi Dave,

Thank you for the heads up, don't know how I missed that one! It's got a broken crown wheel and pinion and it's a 4 stud spring mounting (unusual for a 3.27 diff), whereas I need 6 studs for my Rotflex GT6. I'm going to hang on and hope for a better starting point from which to build a new diff.

Nigel

Link to comment
Share on other sites

Don't worry about rear casing Nigel, there are plenty of spare ones about to allow you to build the diff up before you fit it.

finding the carrier may be more difficult.

I seem to remember there are. Couple of versions of the 3.27 carrier, the one from the Dolomite being the best.

I would check my vague memories first of course.

Link to comment
Share on other sites

2 hours ago, thescrapman said:

I seem to remember there are. Couple of versions of the 3.27 carrier, the one from the Dolomite being the best. 

The 3:27 in my Vitesse was rebuilt by Mike P a couple of years ago with a stronger carrier,i thought he said TR7?.

 

Coould be wrong.

Steve

Link to comment
Share on other sites

Thank you chaps.

Ideally, I want to be able to drop the 3.89 from my GT6 and bolt in a reconditioned 3.27 as a direct swap. I'm trying to avoid cannibalizing my present diff to build the new one.

Life always seems more complicated than it should be, especially when modifying a Triumph!

Nigel

Link to comment
Share on other sites

because the 327 pinion is a larger diameter you either have a thinner crownwheel of a different offset on the diff case CW face the only way you get things to fit in.

likewise a higher ratio needs to transmit more torque for the same performance hence more likely to go bang than a lower ratio 

 

Pete

Link to comment
Share on other sites

I seem to remember a local chap here who races a very nice GT6 putting the higher ratio 3.45 or 3.27 diff in his car which required a larger crown wheel hence some internal surgery with an angle grinder was reqd to make it fit, it was a discussion over coffee at a club early morning drive. I could ask him for clarification as to what he used and what was necessary if reqd. 

Link to comment
Share on other sites

Hi Peter,

The 3.27 crown wheel and pinion do require some machining inside the casing to fit, if using the casing from any other ratio diff. I believe the pinion bearings are different too. My plan is to have Paul Hughes at 2Spec Transmissions build it up for me with one of his limited slip diffs:

http://www.2specgroup.co.uk/transmissions/triumph/

This is for my 2.5 litre GT6, which I feel will easily pull a much higher ratio. The 3.27 diff is said to be the weakest of the small chassis ratios, but my understanding is that it's the differential rather than the crown wheel and pinion that are the Achilles heel. The 2Spec LSD should get over the weakness of the original differential.

I'm not in a rush, so I'm going to keep looking, hoping a 3.27 diff will turn up. In the meantime, 2.5 litres plus a 3.89 final drive does make for amazing acceleration!

Nigel

Link to comment
Share on other sites

There was a rebuilt 3'27 locally here for sale for quite a while on Gumtree but it wasn't cheap around $1100Aus, haven't seen it advertised for a while.

Nigel I never understood why the 3.277 was fitted to the Swiss supplied GT6 models with all them mountains! having driven over them around them and thro them many times in my Vitesse Mk2 with a 3.89 diff the 3.27 long legs just didn't add up! 

Link to comment
Share on other sites

8 hours ago, Peter Truman said:

Nigel I never understood why the 3.277 was fitted to the Swiss supplied GT6 models with all them mountains!

Almost certainly nothing to do with the terrain and everything to do with some legislative quirk. When I was at Rover they fitted different gear ratios to French market cars because of the way taxation classes were calculated there.

Link to comment
Share on other sites

On 17/08/2020 at 15:26, Nigel Clark said:

Hi Peter,

The 3.27 crown wheel and pinion do require some machining inside the casing to fit, if using the casing from any other ratio diff. I believe the pinion bearings are different too. My plan is to have Paul Hughes at 2Spec Transmissions build it up for me with one of his limited slip diffs:

http://www.2specgroup.co.uk/transmissions/triumph/

This is for my 2.5 litre GT6, which I feel will easily pull a much higher ratio. The 3.27 diff is said to be the weakest of the small chassis ratios, but my understanding is that it's the differential rather than the crown wheel and pinion that are the Achilles heel. The 2Spec LSD should get over the weakness of the original differential.

I'm not in a rush, so I'm going to keep looking, hoping a 3.27 diff will turn up. In the meantime, 2.5 litres plus a 3.89 final drive does make for amazing acceleration!

Nigel

Hi Nigel,
I have a 3.27 in my 2.5. It has amazing acceleration in all gears. What gearbox do you have so I can compare?

Thanks,

Iain.

 

Link to comment
Share on other sites

10 hours ago, SpitFire6 said:

Hi Nigel,
I have a 3.27 in my 2.5. It has amazing acceleration in all gears. What gearbox do you have so I can compare?

Thanks,

Iain.

 

At the moment, I'm running completely standard transmission,  including the original gearbox and D type overdrive. Inevitably, this won't last long with the torque from the bigger engine.

As well as the switch to 3.27 final drive with the LSD, Paul at 2Spec will build me a hybrid gearbox, with Dolomite 1850 internals in the original gearbox casing with J type overdrive.

Nigel

Link to comment
Share on other sites

Hi Nigel,

 Your car with 3.89 Diff & GT6 box:
6000RPM: 1st-39.5MPH. 2nd-58.7MPH. 3rd-83.3MPH. 4th-104.5MPH.

Mine with 3.27 & TR6 box:
6000RPM: 1st-39.6MPH. 2nd-61.8MPH. 3rd-93.4MPH. 4th-124.3MPH.

Calculated from http://www.mintylamb.co.uk/gearspeed/

You have better acceleration than me. Not by much in the lower gears though.

I never had a long life with uprated GT6 boxes. Tr box is stronger & OD on 2nd is useful.

Cheers,

Iain

Link to comment
Share on other sites

18 minutes ago, SpitFire6 said:

Mine with 3.27 & TR6 box:
6000RPM: 1st-39.6MPH. 2nd-61.8MPH. 3rd-93.4MPH. 4th-124.3MPH.

I have the Saloon box in my Vitesse as well,pulls like a train but never been near 100mph as it`s scary.Pulls up hills in O/D 4th no problem.

Steve

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...