It's Another 2000 O/D Gearbox in TR Thread

[Barry911]

Hello all, I wonder if anyone can help. I've had a thorough search around, but can't the answer to this specific issue.

 

I've just bought a '74 (so J-Type era chassis / non-overdrive box) TR6. The car's a donor for a coachbuilding project, so originality isn't a particular issue. Floors are going to be replaced, so cut outs for solenoids no problem.

 

I've read about people using 2000/2500 O/D gearboxes in TR's, and have just picked up via E-Bay a 2000 A-Type O/D box. Now, as I was driving over to collect (after committing to it), I realised that I've made the school-boy error of mixing my A' and J's. So I now belatedly realise that I can't mix and match my TR6 gearbox and the 2000 one.

 

So .... I've read that the 2500 gearbox is strong enough to take TR6 type power, but what about the 2000? Are they the same as far as absolute strength goes? I'm guessing the 2000 might have slightly closer and lower ratios? I know the OD's are different specs between the 2000's and the 2500's, but not sure on the actual gearboxes.

 

Finally (!), assuming my overdrive is correct and original to the box, in it's current form (with I'm assuming lower pressure and less springs), if I removed the 2nd gear capability, would it take a TR output? It's a 22% unit, which I reckon is a good thing at least.

 

I'm assuming I've got a number of options:

 

1) Leave 2000 box and overdrive as is other than inspection, put it in with appropriate 'fitting' mods: re-machined output shaft, angled speedo drive and modded speedo using 2000/2500 donor parts, fabricated rear mount and 2500 clutch friction plate. Take chance on how long everything lasts.

 

1a) Leave gearbox as it is, inspection / gaskets / obvious repairs aside, but up rate OD to nearer TR spec, fit as per above.

 

2) Swap this A-type 2000 gearbox for a J-type, mix and match with my TR box, and get closer to a proper TR one, but use two boxes to get one.

 

3) As above but swap my TR gearbox for an earlier (a-type era) one, again using two boxes to get one.

 

4) Sell both 2000 and 6 boxes, put cash towards a J-type TR OD box.

 

To cut to the crux: the 2000 box was £250, sold a good runner 'when it came out of the car' off of E-Bay, which as we know is virtually a cast iron guarantee that it'll be in perfect condition and fault free for next ten years (!). Don't know if that's cheap, sensible or expensive. I don't know how the project is going to pan out, as the shape of the ally body will be new. If it's gorgeous then throwing £1250 at a rebuilt correct OD box will be OK, if it's a minger though, I don't want it owing me fortunes. If I can put something in for few hundred that will probably be OK anyway, then perfect.

 

As for the car, it should be about 100KG's lighter than a 6, and I'm a mechanically sympathetic driver. It's a US car, but I'd expect it to end up around 130-140 honest BHP.

 

I'd very much appreciate your thoughts or suggestions.

 

Oh yes, one slight concern: as I lifted the box out of the car back home, I noticed the output shaft / flange feels solid: no movement at all. Doesn't feel as though it's rocking on locked teeth, but that the actual very last part of the output is solid. Will give it some semi-sensible beans in a minute, and see if it suddenly frees. Suspect that my bargain is already getting expensive!

[LGFromage]

If the gearbox is an original 1974 it will have a metric output shaft to suit the J type box, so an A type overdrive would not fit and option 2 would be the best. If the g/bx has been replaced by an earlier one the A type o/d may be OK, but I would not bet on it. Good luck with your project.

 

Tim

[Lebro]

As you say this has been covered before many times, some by me.

The saloon "A" type overdrives are not as strong as the TR equivalent, I have one in my 3, but had it re-built to TR spec, which included changing the rear casing to get the correct mounting position. Another problem is the speedo drive ratio. Saloon is 3.5:1, (early) TR was 2.5:1 - quite a differance. Also the input shaft of the saloon box has a different No. of splines to the early TR's (not sure about 6's) which required a different friction plate to be fitted.

Suggest you look out previous posts on this for a fuller breakdown of what needs to be done.

 

Bob.

Edited January 5, 2015 by Lebro

[Barry911]

Thanks Bob and Tim. I think I've got something of a handle as to the issues around fitting (splines / clutch driven plate, rear mounting, speedo and solenoid position / orientation, double check clutch release side of things).

 

I believe, mounting and solenoid orientation aside, the O/D differs from TR unit in number of springs, and it's actuating pressure. Initially I did wonder how much of this was deemed neccessary because they operated in second gear (which I never used on my two '4's), and therefore whether just having it switched for 3rd and 4th would circumvent the extra torque issues to some degree.

 

Googling around after I posted, seems to suggest that 2000 and 2.5Pi boxes have the same ratios (but different diffs), which might lend weight to my original hope / query, of whether the actual 2000 gearbox the same spec as the 2.5Pi, and therefore capable of reliably taking 130bhp or so, as per the Pi.

 

Interestingly the OD number on mine is 22/61711/033465 which a Google suggests is a Laycock rebuilt unit. Similarly the main gearbox number has a variety of over-stamps around the normal number area, so I don't know if this means they were both rebuilt at some point.

 

Anyway, original question stands, and I really have tried to find an answer using search etc: is the 2000 box the same as a 2.5Pi box, and therefore safe to around an honest 130BHP?

 

Now, as it happens it all might become slightly moot, as the overdrive output appears to be completely solid. Awaiting reply from vendor who essentially sold it as a good useable unit ....

 

Actually, if it comes to it, I'll strip it, as I did the OD and I think the gearbox on my last TR4, and have a rummage. It's only a £250 unit, but no-one likes feeling misled.

 

Many thanks again,

 

Barry

[Guest ntc]

Barry

Yes it will cope with that no problem,as for the overdrive pay attention here don't get it wrong.Drain the oil stand the box on the output add 1.5 litres of swarfega brake cleaner and leave overnight only then drain,if no movement send the lot to ORS.

[Barry911]

Thanks Neil, that's perfect! I'll report back with what I find.

[Nick Jones]

2500 and 2000 saloon boxes are the same. The 2000 ones have an easier life and are often less worn. The early ones have A-type and later J-type. Overdrives can be uprated to take higher torques by increasing their hydraulic operating pressures - which is probably best left to a specialist.

 

If you have a proper TR6 non-OD box then it ought to be possible to combine the two using the mainshaft, OD and adaptor plate from the saloon box.

 

Nick

[Barry911]

Thank you Nick.

 

My gut feel is that if the two saloon gearboxes are essentially the same, then we know they were engineered to take a good 130bhp over 100,000 miles. For some of that time the engineers would have to allow for it to be pulling a hulking great Pi estate, potentially with kids, mother in law, two dogs, roof rack and a caravan behind.

 

By comparison, mine will be, what, 200 kgs lighter than a saloon, be driven 10,000 miles over four or five years (realistically), and I can take it out and work on it myself if need be.

 

I think what I'll do in the light of now knowing the 2000 box isn't a little sister to the Pi one, is to uprate the overdrive to TR spec, but deal with the rear casing via mounting adaptor, speedo via saloon dial inards in TR one, and clutch via a saloon or Izuzu friction plate.

 

As I say, it's for a coachbuilding project, and frankly there's a degree of risk in how well it'll turn out. If I end up with a sensible O/D box on there as a starting point for, say, £600 or so, then great. If later on I go mad tuning the engine after it's been on the road for a while, I can revisit the box end of things using an A type TR one, and swap the clutch back to TR. We know this box is good for 130bhp, and in it's current format, the engine is 104 at best, so even modestly tuned it won't be more than the 130 I'd guess.

 

This way I retain a complete up and running non-overdrive J era box as an at-the-death backup if it all goes wrong, or for swapsies for an A-era box for the future.

 

Many thanks again!

[Trumpy3]

I fitted a 2000 box with A type to my car with no real problems. The only mods I done were to change the rear case to get the TR mount and speedo drive. I use the car on track days with no problems.

Since changed to a 2500 box with J type...fewer oil leaks. From memory, they reduced the engagement time to reduce the loads on the IRS and improve its durability (the rear end not the OD).

 

The 2500 here had a 28% OD which was OK but I was able to get a unit from an outer car(Volvo I think) that is 25% so fitted that gear set.

 

I run an 2500 sports clutch kit which overcomes the input shaft issue and use the original 2500/2000 thrust bearing set up. With the TR6 I would imagine the TR6 pressure plate could be retained and only the clutch plate need be changed.

 

An interesting point I found was that with the 2500 box and J type, the original TR3A speedo could still be comfortably used without mods.After fitting I went out with a GPS so I could make up a conversion chart. Over here we have gone metric and use KPH. The chart showed that if you take the reading in MPH from the speedo and double it, it is correct in KPH. Reading 50MPH...actual is 100KPH. Thats just how all the different ratios worked out. Do not know how the TR6 works out.

 

I would up-rate the lay shaft and gear.That is a real weak point in the all syncro boxes in TRs and saloons.

[Barry911]

Thanks for that, all useful stuff.

 

A bit of an update, I've now stripped out the OD, and got the lid off the box. It turns out the reason it was seized was that it had been stored empty of oil, and presumably in a shed (or garage) with no insulation and thin walls. The box had lots of moisture inside, and this had led to some rusting, particularly of the OD clutches to their respective bands. Some very gentle heat (could easily hold them), freed them straight off.

 

In terms of mechanical wear on both gearbox, and OD, there appears to be virtually none. The synchro's look new, and the gearbox bearings sound quite good. The selector forks barely have polish marks on them.

 

The overdrive is indeed a 2000 / four spring unit, which will go to TR internal spec, but I'll leave the rear mounting for now, as don't want this running out of control.

 

I've spoken with Peter at ORS, and these are some rough prices (I assume plus VAT, forgot to ask)

 

Set main bearings (mine don't sound bad, but don't sound perfect either) about £50.

Exchange spring peg ring, modified to eight pin: £50

Set eight springs £35

Seal and gasket set: £20

TR type accumulator spring £10

Angle drive: £35

 

So around £200 plus some vat and post. Looks like I'll come in around £600'ish for the whole conversion, and that leaves the 6 gearbox complete for use as a backup or whatever.

 

I'm going to send Peter my spring peg ring, and hopefully will be able to reassemble the thing sooner rather than later.

[Guest ntc]

Barry

As I thought Peter will see you right top man.

[Barry911]

Yes, I realised that I had spoken to him about ten years ago as well! I told him what the OD was from, and he instantly told me the type number it was going to be, and the internal spec. All, of course, spot on.