Overdrive for 4 speed 2000SC?
- Thread starter restojon
- Start date
I doubt you'll be able to fit one directly to the gearbox itself in the way they normally are, but you can buy stand-alone units with a flange at both ends, or you could fit a 5 speed, and in general they're more reliable than overdrive units anyway. If you just want more relaxed cruising and don't mind the loss of performance you could fit a V8 diff.
Probably no reason why it can't be done. I've been playing around with a J type from a Triumph on the back of a TC gearbox and it will obviously require a fair bit of fabrication but it should be possible. The overdrive will 'just' fit in the tunnel but nothing a bit of relieving with a hammer won't fix.
One question Harvey, how critical is it that the rear nut on the Rover box is tight? I know it needs to be tight to hold the speedo gear in place but if that were not an issue, is it required to hold the bearing in place?
One question Harvey, how critical is it that the rear nut on the Rover box is tight? I know it needs to be tight to hold the speedo gear in place but if that were not an issue, is it required to hold the bearing in place?
I was thinking of the flange at either end type H.
I'd like to keep the standard gearing but would like to add a more relaxed cruising gear for motorway hauls, I've fitted many of these ( J types and the like) to pre war cars but they generally have a ton of room underneath to accomodate. I had a look underneath when I had the car on a ramp recently and it looked like you could squeeze one in with a gentle bit of "accomodation assisted by hammer". It was just that I'd heard no one mention it and a forum search found no results so I wondered if there was a technical reason why it isn't a common conversion, I did buy a good LT77 box recently to fit to give another gear but after a bit of headscratching I thought an O/D would be the way to go, it's not exactly a huge prop so getting one the right length shouldn't be any problem, there may even be an "off the peg" item from another vehicle that could be used. It's going to be a while before I do the conversion but a friend has a J type sitting on a shelf which I can mock up with and get some ideas.
When you mention fabrication are you talking about mounting points?
I'd like to keep the standard gearing but would like to add a more relaxed cruising gear for motorway hauls, I've fitted many of these ( J types and the like) to pre war cars but they generally have a ton of room underneath to accomodate. I had a look underneath when I had the car on a ramp recently and it looked like you could squeeze one in with a gentle bit of "accomodation assisted by hammer". It was just that I'd heard no one mention it and a forum search found no results so I wondered if there was a technical reason why it isn't a common conversion, I did buy a good LT77 box recently to fit to give another gear but after a bit of headscratching I thought an O/D would be the way to go, it's not exactly a huge prop so getting one the right length shouldn't be any problem, there may even be an "off the peg" item from another vehicle that could be used. It's going to be a while before I do the conversion but a friend has a J type sitting on a shelf which I can mock up with and get some ideas.
When you mention fabrication are you talking about mounting points?
I'm trying to do it like they would have done at the factory so by fabrication, I mean making an adaptor between overdrive and gearbox and a new output shaft for the 'box too. I should be able to keep the original gearbox mount (or at least part of it).
At this point all i've done is keep hacking away at the Triumph adaptor until things line up, then i'll need to talk to someone about welding it on to the back plate of the gearbox with lots of bracing. It's probably not the easiest way though... If you can get a double flange unit it would make things much easier. I imagine that would only require a driveshaft and some mounts for the unit.
At this point all i've done is keep hacking away at the Triumph adaptor until things line up, then i'll need to talk to someone about welding it on to the back plate of the gearbox with lots of bracing. It's probably not the easiest way though... If you can get a double flange unit it would make things much easier. I imagine that would only require a driveshaft and some mounts for the unit.
Aha, I see your point. Your way is a nice way of doing it actually. I was thinking of the double flange purely in terms of convenience and ease of maintenance. There's a long way to go yet till I get there but it's something I really want to do in the future as I think it will improve what's an already good setup.
Rover got a fair way down the route of fitting an overdrive to the 2000 and it isn't clear why they didn't put it into production.
In practical terms today, the easisest fix is definitely that of fitting the V8 diff. The lower gear ratios seem to be low enough for this not to be a significant problem, at least with 2000SC, 2200SC and 2200TC, but you'd probably have to fit 2200TC carbs to a 2000TC in order to make the engine sufficiently flexible at low revs. Demetris is the originator of this set up and has some threads on it.
In terms of where to mount a double flange overdrive unit, I'm a little nervous of having two very short propshafts. That can give problems with balancing. In view of the relative frgility of the Rover box, I think I might want to mount the overdrive in unit with the diff, on the front of the extension, or even replacing some of the extension. The diff extension is much easier to modify than the back of the gearbox as all it contains is a single shaft that should be easy enough to machine a replacement for. If necessary you could even mount the overdrive back to front with the gearbox end facing the diff if you wanted to use the gearbox adaptor from another vehicle. The O/D is epicyclic, so it shouldn't mind which way it drives. That way you could get it to sit under the back seats where it might be easier to create space. but you'd really have to stand thoughtfully under the car with one for an hour or so, eying up where the space is.
Chris
In practical terms today, the easisest fix is definitely that of fitting the V8 diff. The lower gear ratios seem to be low enough for this not to be a significant problem, at least with 2000SC, 2200SC and 2200TC, but you'd probably have to fit 2200TC carbs to a 2000TC in order to make the engine sufficiently flexible at low revs. Demetris is the originator of this set up and has some threads on it.
In terms of where to mount a double flange overdrive unit, I'm a little nervous of having two very short propshafts. That can give problems with balancing. In view of the relative frgility of the Rover box, I think I might want to mount the overdrive in unit with the diff, on the front of the extension, or even replacing some of the extension. The diff extension is much easier to modify than the back of the gearbox as all it contains is a single shaft that should be easy enough to machine a replacement for. If necessary you could even mount the overdrive back to front with the gearbox end facing the diff if you wanted to use the gearbox adaptor from another vehicle. The O/D is epicyclic, so it shouldn't mind which way it drives. That way you could get it to sit under the back seats where it might be easier to create space. but you'd really have to stand thoughtfully under the car with one for an hour or so, eying up where the space is.
Chris
KiwiRover said:
It needs to be tight, otherwise, in addition to the speedo gear spinning on the shaft, when you select 2nd or 4th (usually second for some reason) the mainshaft can move forwards and you end up with no synchro, and difficulty in engaging the gears. Sometimes the shaft is tight enough in the bearing to stop it moving, for a while, and then if the bearing gets a bit loose in the casing the bearing could start moving about as well, causing the same thing, and wearing the register in the case. Worth tightening it if it's loose, it becomes a little bit more of a problem if the stud has sheared off the back of the mainshaft.
Willy Eckerslyke
Well-Known Member
I went through the same thought process as I have a few Stag/Dolomite Sprint overdrives knocking about, so lined one up against a P6 'box and decided it would just need a new spacer/adapter and mainshaft. But where it all falls apart is with the transmission fluid, the overdrive isn't going to like engine oil - I doubt if it would work at all with it - and the P6 gearbox doesn't like normal transmission fluid.KiwiRover said:
Insurmountable?
I was thinking of fitting the "flange either end" type of O/D straight onto the output flange of the gearbox and shortening/replacing the prop to something suitable. The ones I've fitted have had their own oil within the unit, something along the lines of this:
http://www.odspares.com/phdi/p1.nsf/sup ... ent&part=4
http://www.odspares.com/phdi/p1.nsf/sup ... ent&part=4
I think the only problem with bolting one of those straight onto the gearbox flange is that the mounting would have to be very carefully set up, otherwise the slightest movement of the gearbox will be putting massive loads on the bearings.
There is also no reason why the oil supply can't be seperate with the OD mounted straight to the box. You just need to put a filler plug in the adaptor and keep the rear oil seal on the gearbox, but like Harvey said, you can use EP90 in the P6 box.
There is also no reason why the oil supply can't be seperate with the OD mounted straight to the box. You just need to put a filler plug in the adaptor and keep the rear oil seal on the gearbox, but like Harvey said, you can use EP90 in the P6 box.
Willy Eckerslyke
Well-Known Member
Thanks, perhaps the idea isn't dead in the water then after all (Laycock J-type overdrive mated to P6 gearbox).
My idea had been to cut up one of the Triumph adapter plates and a Rover gearbox end plate (the bit with the hole for the rubber bush) and bodge them together as a mock-up. I have a contact who's an ace at aluminium welding, so might even get this to be a working solution. If not, getting one cast or machined from solid billet would be a very expensive solution.
Then I'd mock up a mainshaft with scrap Rover and Triumph mainshafts cut and fixed together and get a quote from a custom transmission shop to do the job properly. I don't have a Triumph mainshaft, but could surely get a scrap one from somewhere.
I'm about to go on holiday, but when I return I'll gather up the bits and have another look. Then perhaps we can exchange notes?
My idea had been to cut up one of the Triumph adapter plates and a Rover gearbox end plate (the bit with the hole for the rubber bush) and bodge them together as a mock-up. I have a contact who's an ace at aluminium welding, so might even get this to be a working solution. If not, getting one cast or machined from solid billet would be a very expensive solution.
Then I'd mock up a mainshaft with scrap Rover and Triumph mainshafts cut and fixed together and get a quote from a custom transmission shop to do the job properly. I don't have a Triumph mainshaft, but could surely get a scrap one from somewhere.
I'm about to go on holiday, but when I return I'll gather up the bits and have another look. Then perhaps we can exchange notes?
That's basically my plan. I took my bodged Triumph adaptor and Rover backplate to a welder today and he seemed to think that it was all perfectly do-able so I will finesse it a bit more before I hand it over to him. I'll have to get some pictures of the work in progress.
Willy Eckerslyke
Well-Known Member
Great stuff, I'll watch with interest. Good luck!
Mind you I've just noticed how much the standard Triumph J-type adaptors sell for (150 US dollars). Perhaps I won't be so quick to chop one up after all, not until I'm more certain of the results anyway.
There's a link here about a similar conversion on a Bristol which may include some useful tips:
http://www.jel450.com/technical/technical.html
Mind you I've just noticed how much the standard Triumph J-type adaptors sell for (150 US dollars). Perhaps I won't be so quick to chop one up after all, not until I'm more certain of the results anyway.
There's a link here about a similar conversion on a Bristol which may include some useful tips:
http://www.jel450.com/technical/technical.html
Brian-Northampton
Administrator
If you use EP90 in the gearbox / Overdrive, I'd make sure it's GL4 and not GL5. Apparently GL5 has a habit of eating yellow metals - and I think we've a few of those.
Cheers,
Bri.
Cheers,
Bri.
