Overdrive virgin

[Clive]

18 hours ago, RobPearce said:

The theory is one I tend to agree with. When I fitted an overdrive gearbox to my first Vitesse, it was straight out of a scrap car. While it looked good, the mainshaft rear bearing was past its best. The result was a fairly rapid (and fairly terminal) failure of the mainshaft tip bearing. That failure is not exclusive to OD boxes but does seem more common on them. The reason being that the non-OD mainshaft has two proper bearings to keep it aligned, where the OD one has only one - the front end sits in the weak tip bearing, the back end in the overdrive cone assembly.

In addition, and again anecdotally, my friend who has rebuilt probably 50+ triumph gearboxes, reckons the layshaft pin on od boxes suffers more wear than non-od . Maybe it is greater lateral forces caused by the longer gearing? But he still strips non-od boxes and finds the internals are much better than from OD boxes. Of course, it may just mean OD boxes do more miles, but it is too common. 

[glang]

7 minutes ago, RobPearce said:

Yes, a popular option because of relatively good availability, plus it's a good match. I have 3.63 diffs (and J-type overdrive) on all three of my Triumphs.

What do you think are Jason's chances of finding the required adaptor plate and mainshaft these days Rob?

[RobPearce]

1 hour ago, glang said:

What do you think are Jason's chances of finding the required adaptor plate and mainshaft these days Rob?

Could be tricky. All three of mine came from Canley's as "conversion kits" (fully built up gearboxes), the most recent one over a decade ago. The actual J-type unit is fairly easy because they were still used on production Volvos into the 1990s.

[glang]

Think Jason has already got the J type unit but dont know if he has the correct adaptor. I would go for a D type conversion these days just because its easier to get all the bits...

[Jason C]

21 hours ago, glang said:

I believe the usual diff change on a Vitesse 2L non OD is to a Spitfire 1500 item with a 3.63 ratio which makes first gear more effective and drops cruising revs although no where near as much as OD.

To fit your 3 rail gearbox with a J type OD isnt easy as this arrangement was only used on a few models and over a short time. I think youre going to need a particular adaptor plate to fit between the main case and the OD plus the corresponding mainshaft which is different from the standard D type version. Then the gearbox mounting is different and of course propshaft shorter...

Shouldnt be any problem getting the OD overhauled by a specialist. 

Very interesting info @glang I wasn’t aware this was a popular conversion. When I first discovered the diff was from a Spitfire, my thoughts were “oh no, what’s a Spitfire diff doing on the car!”

To clarify is the 3.63 ratio diff a preferred ratio for a Vitesse than the 3.89 fitted from the factory? A good compromise between starting acceleration and cruising in 4th gear? How does it compare to the 3.89 ratio? Is the diff itself the same strength coming from a 1500 Spitfire, just with a different ratio? 

Did Triumph document diff serial numbers, I came across this but it looks to be incorrect listing the FD prefix as a 3.89 for the Vitesse, 2 Litre: http://www.wolfitt.com/numbers_and_ratios.htm

I’ve been told the 3.27 is the best of the lot, but hard to source.

Thanks

Jason

 

[Jason C]

21 hours ago, RobPearce said:

Yes, a popular option because of relatively good availability, plus it's a good match. I have 3.63 diffs (and J-type overdrive) on all three of my Triumphs.

Thanks @RobPearce fascinating, as mentioned to glang I wasn’t aware this was a common conversion. I suspected a previous owner just put a random diff on or something. Would you mind going into a little more detail on why the 3.63 is good match? So I should keep the diff on the car, good for driving now and later with the OD conversion?

 

[Jason C]

22 hours ago, glang said:

To fit your 3 rail gearbox with a J type OD isnt easy as this arrangement was only used on a few models and over a short time. I think youre going to need a particular adaptor plate to fit between the main case and the OD plus the corresponding mainshaft which is different from the standard D type version. Then the gearbox mounting is different and of course propshaft shorter...

The J-Type units are becoming harder to find, at least in New Zealand, the adopter plate being the biggest challenge. I was lucky, a fine local chap was kind enough to sell to me.

The parts for the Overdrive conversion I have so far: J-Type unit, Stanpart adapter plate (313085), mount plate and bracket, and the main-shaft. And a second hand Lucas steering wheel stalk.

I think, I still need to source: Speedo adapter and right angle drive, and the electrical cut-out switch and bracket on the remote housing and shaft.

Not sure where to buy the Speedo adapter, as I’ve read these can cause problems, wearing out if incorrect? Would I need to buy a different Speedo cable? Lastly, not sure about the cut-out switch, second hand only?

[glang]

Diff: yes the FD is a 3.89 which is the standard ratio for a Vitesse. The 1500 Spitfire unit is said to be a stronger unit than the earlier designs but only comes with 4 stud holes for mounting the spring. Some people swop the casings, drill and tap additional holes or use it as it is.              The 3.27 ratio is probably going too far unless the engine has been tuned or changed to 2500cc. The ideal set up is obviously a personal choice...

Anyway you look all set to install OD and the only large component youre missing is the 3" shorter propshaft.

 

[RobPearce]

2 hours ago, Jason C said:

Thanks @RobPearce fascinating, as mentioned to glang I wasn’t aware this was a common conversion. I suspected a previous owner just put a random diff on or something. Would you mind going into a little more detail on why the 3.63 is good match?

Previous owners have often fitted odd things. Until I changed to the 3.63, my GT6 had been fitted with a Herald 13/60 4.11 diff by a PO. That made for very easy wheel spin (which rather detracted from the "faster acceleration") and a very busy feel at speed, even with the overdrive. The extra legs from a 3.63 diff makes motorway speeds a lot more pleasant, without all that much loss of acceleration. The Vitesse feels the low speed loss a bit more, being both heavier and a Mk1 engine, but outside of a traffic-light-grand-prix it's not something you'd really notice. As glang said, going all the way to a 3.27 would make it feel just a bit sluggish off the mark, which you don't want. Hence the 3.63 is a nice sweet spot.

2 hours ago, Jason C said:

I came across this but it looks to be incorrect listing the FD prefix as a 3.89 for the Vitesse

It is incorrect, in that the Vitesse diff should have an HC prefix. Whether the FD is a 3.89 I'm not sure - FD would be a Spitfire Mk3 prefix on everything else, but Mk3 Spitfires had 4.11 diffs with an FC prefix.

[Jason C]

1 hour ago, glang said:

Anyway you look all set to install OD and the only large component youre missing is the 3" shorter propshaft.

Thanks glang, typically do people have the original propshaft cut down and balanced? I guess ideally, if a spare propshaft could be sourced and that reduced, should you want to revert in the future. 

[Jason C]

1 hour ago, glang said:

The 3.27 ratio is probably going too far unless the engine has been tuned or changed to 2500cc.

Thank you, very good information to know. 

[Dave Clasper]

My Mk1 2 litre Vitesse, appears to have had a J type box and a 3.27 dif fitted by Canley at around the same time about 20 years ago.

Good for cruising and will pull long M way inclines in O.D, if enough revs to begin with, though a tad sluggish of the mark maybe to do with dif ratio? (Never driven another Vit, so can't compare).

Some say 3.27 dif the weakest of the lot?.

My O.D wasen't working for a while and I didn't notice much, if any difference in fuel consumption on longish M way trips, though I may have been keeping the revs down a bit to compensate, can't really remember, it was a while back.

Good luck with it Jason

Dave

[glang]

4 hours ago, Jason C said:

Thanks glang, typically do people have the original propshaft cut down and balanced? I guess ideally, if a spare propshaft could be sourced and that reduced, should you want to revert in the future. 

As you just need a standard 1.1m OD propshaft these come up secondhand or can be ordered new for around 160 pounds although in both cases delivery could be expensive. Otherwise a specialist prop place, if you have one close by, could do the job on yours possibly for less cost however do check that the sliding joint is good and that quality UJs are used....

[Jason C]

23 hours ago, Dave Clasper said:

My Mk1 2 litre Vitesse, appears to have had a J type box and a 3.27 dif fitted by Canley at around the same time about 20 years ago.

Thanks for the insights and well wishes @Dave Clasper. I’m sure I’ll need luck on my side. 🙂 Wow, Canley has been around a while. A few years back I enquired about their OD kit, but they had stopped selling them at that stage. 
 

Curious, was the OD conversion popular on cars when they left the factory? Or did they become a addition years later? 

 

[thescrapman]

Some models were nearly always specified with OD, others rarely. 

Most TR6 seem to be OD. And PI saloons.

not so many Vitesse, hardly any Mk3 Spitfire.

 

[Guppy916]

This is on my MK3 GT6 with a 2500 engine fitted, uprated J Type o/d, I used a Sparco Steering wheel with two buttons on, I use one for the horn and the other for o/d, If you fit o/d you should use the over drive inhibitor switches which disengage's o/d the moment you touch the clutch pedal, so you can never leave it on, I also made another brass contact ring to fit in the steering coloum as the photo shows, one contact for the horn the other for o/d, the steering wheel from Demon Tweeks, inhibitor switches from Rimmer's, This all  works great, o/d only on 3rd & 4th

[Hogie]

Hi Guppy,

I ike the steering wheel.

How have you got the inhibit switches to dis engage OD when pressing the clutch?

The standard arrangement would leave it in OD until you switch it off.

Are you using some form of Logic Box?

 

Roger

[Slimboyfat]

J Type 3 rail adapter plates are due in from the machine shop this week. It took a long while to get our casting company interested in doing a run this time (mainly due to relatively small moq) hence the lack of stock for the past year or so. Everything else for the conversions shouldn't be a problem.

[Slimboyfat]

Oh and D type overdrives can use the J type adapter plate if you are going down that path, but not the other way round (J on a D).

Edited December 8, 2021 by Slimboyfat

[Slimboyfat]

On 06/12/2021 at 10:35, Jason C said:

@Dave Clasper. I🙂 Wow, Canley has been around a while. A few years back I enquired about their OD kit, but they had stopped selling them at that stage. 
 

 

 

We had to stop because we were simply running out of core. In the end something like 50% of everything that went into a conversion was new (mainshaft, adapter plate, layshaft, re-bushed clusters, prop, all the switch gear, etc, etc). 

At the height of it we were doing anything up to ten conversions a week, and we were doing them for over thirty years (if you include the JK time). That eats up a lot of core!

[Slimboyfat]

On 05/12/2021 at 09:52, Jason C said:

Thanks glang, typically do people have the original propshaft cut down and balanced? I guess ideally, if a spare propshaft could be sourced and that reduced, should you want to revert in the future. 

We stopped modifying props to go with conversions some ten years before we stopped selling them. This was simply because by the time a prop has got to be thirty plus years old chances are that the slider, u/j's, and in some cases flanges are generally all knackered. At this stage you might end up with just the tube which is the cheapest bit (used to cost us a tenner!), and that made it simply uneconomic to refurbish them.  Every conversion after that got a brand new prop, and I have several stillages full of old ones waiting for the time when I can get them out of the back of the warehouse, and weigh them in.

[Guppy916]

Hi Hogie, Yes i used a o/d Control box, details below,

and yes as soon as the clutch is pressed it disengages o/d, I have two inhibitors switches so that I can't engage o/d in 1st - 2nd or rev, so no chance of o/d in reverse. 

Here's a set on ebay with brkt https://www.ebay.co.uk/itm/224719844400?hash=item345258b430:g:ObIAAOSwlUhhnlsz

and some info on the o/d controller https://www.revingtontr.com/product/rtr1001k/name/logic-switch-overdrive-all-types

?

 

 

 

 

 

 

 

 

 

 

 

 

 

[Guppy916]

Hogie I also fitted three of these small LED's as photo,

From the top Overdrive, Engine Cooling Fan & Fuel Pump 

they are from https://www.carbuilder.com/uk/green-mini-led-warning-light

 

[Hogie]

Hi Guppy,

that makes sense. I have a home made Logic box that does the same as the TRRev box.

I fitted the indicator LED in the indicator escutcheon on the steering column (TR4A)I just couldn't drill a hole in the dash  

 

Roger

 

[Jason C]

On 07/12/2021 at 10:14, thescrapman said:

Some models were nearly always specified with OD, others rarely. 

Most TR6 seem to be OD. And PI saloons.

not so many Vitesse, hardly any Mk3 Spitfire.

 

Thanks for the insights into the history @thescrapman makes sense as I had seen quite a few PI gearbox overdrives around.