Differential queries

[kevin]

Hi

Doing a full restoration on my mk3 non rotoflex with overdrive, removed diff from chassis and done first clean up. There is red paint on the input drive hub castellated nut and KC73323 stamped into the casing. I am being told that it is a 3.27:1 diff not the 3.89:1 which it should have with a KD stamp and blue paint so clearly the car has had an overdrive unit fitted or diff replaced with a different unit. I am told this will result in less acceleration but more comfortable cruising both of which are fine with me, but I wondered if anybody else has had a car with this configuration and their thoughts on its drivability?

Doing some preliminary checks, when you start to rotate the input shaft very slowly one of the half shaft flanges start to turn and the other does not,  I would imagine this is down to backlash on the sun / planet gear(s)? If I then increase the speed both half shaft flanges turn normally, then go back to turning very slowly as before both half shaft flanges continue to turn? Appreciate any thoughts / checks to do before I open the unit up.

[Pete Lewis]

paint on  nuts is a normal  factory applied dab by someone who has torqued the fixing to the specification , different colours depending on if it was operator or inspection 

used as a standard by many in the 70/80s 

to check the ratio both outputs shafts must turn together and each turn in tandem

just turning and the fact one is seemingly easier is not a concern

there is often some free play on planets   again not of any real concern .

3.27 ;1 plus overdrive is a bit high geared  can end up with excessive throttle opening as the higher the ratio the more torque it has to transmit and

economy/performance is surprisingly lost 

why do you feel you need to strip the diff down .   ??? 

pete

 

[Clive]

Think of the gearing as non-overdrive GT6, but then you can have even longer gearing if you wish at the flick of a switch. But as Pete points out,, be prepared to drop it out of overdrive for inclines and so on.

The diff sounds normal to me. On quarter shaft is just gripping slightly more than the other, they are very unlikely to be exactly the same. Even a freshly built diff will do that.

[kevin]

Thanks for responses.

My son (who will end up with the car) is trying to talk me into rebuilding the engine to a Stage 2 level of tune, would that alter any of your advice?

Will probably not strip it now but was thinking of doing the oil seals on the drive shafts and input shaft, no sign of leakage but the car has been off the road for 28 years and I want a restoration with minimal revisits (yes I know it’s a Triumph!). I gather the input shaft nut can be a little tight to remove.

[johny]

Id recommend doing the input shaft seal as its easy and is much more likely to leak (3.27 times more revolutions?) but the output shafts are a lot harder and luckily I havent found they have a problem even after 50 years. And yes the nut will require a 1 1/8" (or 30mm?) socket and bar plus some way of holding the flange for which there are special tools (see ebay) or various other less professional methods😏

[Pete Lewis]

the coupling nut is not that tight ,  90/100lbft    first is it nyloc or castle nut and pin ??  as refit have different rules to apply here 

two bolts thro the coupling holes and jammed with a lever it will suffice 

output shaft seals require a pig of a circlip removing and then a strong thin legged puller or a vice and club hammer to get the shaft out its bearing  then you can replace the seal

its a siimple assy but can be a headache to dismantle the short shafts .

so if its compromise or utopia you can decide  

pete

 

[johny]

Pete are the output shaft bearings generally any good after they've been removed or are new ones required with the seals?

[SpitFire6]

Hi,

 my GT6 2.5 had a 3.63 +OD. Now a 3.27 +OD. Perfect for the motorway. If I need to accelerate quickly I use the gearbox.

I believe the GT6 was 3.89 with OD & 3.27 without. Minty lambs calc is wrong in this respect.

Check your speedo as this is calibrated to the rear-drive ratio. My speedo reads low with the 3.27.

Cheers,

Iain.
 

[Gully]

My GT6 ran OD with a 3.27 diff when I first had it. I found the OD was only ever used on 60 and 70 mph roads, plus 1st was pretty tall (even though that would have been standard for a non OD car). I'm much happier with the 3.63 diff I'm running now - better acceleration, OD is used more often on 3rd and 4th, but still relaxed cruising on dual carriageways and motorways.

Gully

[Pete Lewis]

out put bearings  ..well if the are dragged off with sucess they should be fine ,if they have been in a vice and bashed all round the garage ...probably not 

they dont seem to suffer much in normal wear life , if not leaking i would tinker with something else and leave alone 

there is no gasket for the bearing hsg  but if you remove a smear of sealer , like loctite 574 (love it) is worthwhile , not to use something slippy of a hard face joint

Pete

[johny]

I look with envy at the WSM where the proper Triumph tools pull bearings on the inner races not like using a legged puller on the outer ones which seems a bit animalistic☹️

[Steve P]

16 hours ago, SpitFire6 said:

Hi,

 my GT6 2.5 had a 3.63 +OD. Now a 3.27 +OD. Perfect for the motorway. If I need to accelerate quickly I use the gearbox.

I believe the GT6 was 3.89 with OD & 3.27 without. Minty lambs calc is wrong in this respect.

Check your speedo as this is calibrated to the rear-drive ratio. My speedo reads low with the 3.27.

Cheers,

Iain.
 

Sorry for the hijack but i see in Ians reply he has a quaife in a 3:27,i have a Blackline atb ready for my 2.5 +o/d Vitesse with a 3:27 already in there but i was told it can`t fit in due to the carrier?,I have a stronger carrier already fitted by Mike Papworth,Will it fit?.

Steve

[Ian Foster]

Hi Kevin

I have a 3.27 in my 1969 Mk2. I bought in 1977 as a non O/D car which I fitted with a box and D-Type from a Vitesse. I tried a 3.63 in the 80’s but went back to the 3.27 (actually when the 3.63 was found to have incorrect output shafts.

It gives 70mph at about 2800 rpm and generally copes OK on hills etc. As others have said it’s easy enough to just flick it out of O/D. I get pretty good touring mpg (35 on the 2016 RBBR and 38 in 2018) with just a mildly breathed on 2L engine, running 175 CD2 carbs. Being the original spec for the car the speedo reads correctly (and accurately according to the Satnav).

It is supposed to be the weakest of the diffs, but mine is a recent Canley build with the improved carrier and has been OK so far.

Ian

[SpitFire6]

2 hours ago, Steve P said:

Sorry for the hijack but i see in Ians reply he has a quaife in a 3:27,i have a Blackline atb ready for my 2.5 +o/d Vitesse with a 3:27 already in there but i was told it can`t fit in due to the carrier?,I have a stronger carrier already fitted by Mike Papworth,Will it fit?.

Steve

Hi Steve,

Canley supplied & fitted the Quaife around ten years ago. I remember asking about possible machining required. I don't remember it having any done.

You could ask the horse, Dave? The horse as in the mouth. 
 

Cheers,

Iain.

 

[SpitFire6]

 

 

 

 

️

3

29 minutes ago, Ian Foster said:

Hi Kevin

I have a 3.27 in my 1969 Mk2. I bought in 1977 as a non O/D car which I fitted with a box and D-Type from a Vitesse. I tried a 3.63 in the 80’s but went back to the 3.27 (actually when the 3.63 was found to have incorrect output shafts.

It gives 70mph at about 2800 rpm and generally copes OK on hills etc. As others have said it’s easy enough to just flick it out of O/D. I get pretty good touring mpg (35 on the 2016 RBBR and 38 in 2018) with just a mildly breathed on 2L engine, running 175 CD2 carbs. Being the original spec for the car the speedo reads correctly (and accurately according to the Satnav).

It is supposed to be the weakest of the diffs, but mine is a recent Canley build with the improved carrier and has been OK so far.

Ian

Hi Ian,

My Wheel/tyre combo is the same diameter as 155/80/13's. I wonder why your RPM @ 70 is higher? Smaller diameter? Maybe I am quoting indicated speed and not actual?

Cheers,

Iain.

 

[SpitFire6]

No idea where the hand came from! + I cant;t edit my post.

[NonMember]

Overall gearing of a non-OD GT6 with 3.27 diff was 20.15mph/1000RPM according to the WSM. With overdrive added, ratio of 0.802 for D-type, this becomes 25.12mph. At 2800RPM that translates to 70.3mph, as Ian said.

[SpitFire6]

Hi,

 All my GT6 boxes were J-type. Maybe I have the higher ratio OD?

I can remember the GT6 box blowing up at least three Four times. I have a TR6 box now. The lower 1st & 2nd make up for any lost RPM moving from a 3.63.
I was living in the Netherlands & the Autobahn was local. 3.63 was not tall enough.

I can't remember which diffs I was using when they went US. It's only had the 3.27 with the TR6 box. 3.27 has been replaced once due to noise & 3.63 twice when teeth fell out. Quaife fitted over ten years ago and diff has a whine now. Only under load or overrun. I don't remember, but it is one OR the other!  I imagine the pinion clearance has increased? Started knocking a few years ago because the garage had used screws and not bolts on the input shaft to the diff.

3.27 probably no good in a racing car. Always wanted one with the 1500 engine.

Cheers,

Iain.

[NonMember]

13 hours ago, SpitFire6 said:

All my GT6 boxes were J-type. Maybe I have the higher ratio OD?

There are, I believe, two gear sets for the J-type. The most common one, which was OE for late Spitfires, is so close to the D-type that you wouldn't notice. However, some (later?) 2000 range got what is known as the "27%" version - gearing of 0.787. Maybe that's what you've got.

[Nick Jones]

19 hours ago, Steve P said:

Sorry for the hijack but i see in Ians reply he has a quaife in a 3:27,i have a Blackline atb ready for my 2.5 +o/d Vitesse with a 3:27 already in there but i was told it can`t fit in due to the carrier?,I have a stronger carrier already fitted by Mike Papworth,Will it fit?.

Steve

Steve, the clues are in the original CT thread.

https://www.club.triumph.org.uk/menu/6023/item/605008/view

Can be done but machining needed on the carrier.  You could contact 2Spec (dunno if they are your original supplier) as they have done before......

According to Canleys, there are 3 possible ratios for the J-type. 25%, 28% and 27%. The latter used on later applications (Volvo), but possible to fit.

28% were used on the 2.5 cars and Stag so seems likely that you have one Ian - as Rob says. It’s marked on the OD nameplate at the end of the serial movement.

Nick

[Pete Lewis]

care off canley's 

Stay home, and stay safe, and use this time to get your Triumphs ready for when this is all over!

 

Home/Archives/Technical Archive

The J-Type Overdrive

Trials and Tribulations

The J type overdrive was standardised on all Triumphs from 1974 so that this article covers Spitfire from FH60000, all Dolomites, later 2000/2500, late TR6 and Stag. These overdrives have also been retro fitted to many earlier cars, and can be distinguished by the solenoid on the LHS (all D type and A type have the solenoid on the RHS). I will not attempt to cover all the minor variations in specification as there are also units fitted which originally came from Volvos, Ford Transits and Sherpa vans, just to deal with common problems and what to do about them. In the Triumph range the units fitted to single rail gearboxes (Dolomite and Spitfire with reverse by 3rd gear) have a different rear housing fitted so that the gearchange can be bolted on the top, apart from this all other units can be interchanged (but pay attention to different rear flanges and speedo drive ratios) if the operating pressure is set correctly. (The more torque an engine produces the higher the operating pressure required). Oil leaks - before attempting to trace a leak make sure that the gearbox/overdrive unit has a breather somewhere that is clear. Blocked or missing breathers cause oil to be forced out.

The J-Type Overdrive

If an overdrive fails to operate the first thing to check is the electrical circuit, most cars do not have a relay fitted (it isn't necessary with the low power consumption of the solenoid) but as a lot of solenoids make very little noise when engaging a circuit test is often required. (Note that Sprint/2000/2500/Stag have a separate switch on the gearchange for overdrive 3rd and overdrive 4th, all other cars have one cut-off switch). The units themselves are fairly reliable (the filtration system is excellent) and it is the solenoid which causes most of the problems. If there is power to the solenoid and the overdrive either won't engage, engages cold and not hot, or won't disengage then the solenoid is very likely the culprit. To remove and replace this a 1 inch spanner is required but it must be no more than 3 mm thick.

The original solenoids have the outer metal case held in position with four small roll pins, if the case is very loose (which can cause incorrect operation) then it is possible to tighten it up with care and it may work again. The only other DIY option is to remove a tiny internal circlip and withdraw the operating piston, there are then two external and two internal O rings to replace if you can get hold of them - if you don't fancy doing all this (and there is about a 30% chance of it working properly again after fiddling with) then replacement is the only option. New solenoids are around £75, but the outer case is swaged on and does not come loose. All J type solenoids are interchangeable. Later Dolomite and Spitfire overdrives (after 1978) have a badly made centre to the one way bearing and from around 30000 miles can give the impression of clutch slip, quick getaways from the lights can lead to an embarrassing lack of forward motion. This problem and in reality all other faults mean the unit has to be removed from the car. Although it just about possible to remove the sump and gain access to the fine filter (RHS), pump ball bearing (centre) and relief valve (LHS) it is very unlikely that anything can be gained by doing so. (Very occasionally the relief valve may stick which means the unit can't work). The whole assembly is not too bad to work on and as long as all bits are put back in the right order and the right way round (without too many left over) then it should work again. The one way bearing is awkward to refit, a piston ring compressor can be used if all else fails.

If you really have the inclination and a 0 - 1000 PSI pressure gauge and a fitment to screw into the test point (the plug just under the front of the solenoid) then the operating pressure can be tested, around 350 PSI for a 1500 engine going up to say 550 PSI for a Stag. Altering the pressure requires fiddling with the relief valve (two types fitted) and is beyond the scope of this article. Noisy bearings can be replaced by competent amateurs, other failures, rare but often fatal are probably best left to professionals.

Note for information there are two different ratios of J type fitted, with 2.5 cars having a 28% ratio and all others 25%, (the first two figures of the plate on the RHS of the front case is the ratio). In addition some later Volvo units are 27%.

Use good oil in the gearbox/overdrive, it is worth the extra (particularly synthetics) as it is working very hard and changing it every 50000 miles is well worth the effort.

John Kipping

[Colin Lindsay]

Changing it every 50,000 miles????

Must make a note in the calendar for 2120.

 

[Pete Lewis]

you can set your alarm clock  ?????

Pete

[johny]

2 hours ago, Colin Lindsay said:

Changing it every 50,000 miles????

Must make a note in the calendar for 2120.

 

That sounds a bit more sensible than this changing it every year business!

[Steve P]

Thanks to Ian and Nick for those replies,i forgot about the CT thread as i don`t really check there any more.

I will contact 2spec.I don`t really want to take it off the road until the end of the year though.On the speed/revs thing,i have a saloon box with J type and 13 inch wheels with 175/70 tyres,70 mph is 2900 RPM,that`s with an electronic speedo and rev counter, and checked with Sat Nav.

Latest problem is i have lost the bloody keys,i have to change the ignition switch and door and boot locks.

Steve