Overdrive Gear Box

[Andrew]

I would like to ask the opinion of the group about the Overdrive Gear Box Option. If one had access to an overdrive, is it worth the trouble doing the conversion. I have access to one but I am not sure if it will work in the S3. I would need to shorten my drive shaft but I believe I have all of the other components. The only other issue is that the Overdrive is out of a SII, will it work with the S3. In other words are the overdrives the same and can they be interchanged. Yes, as you can see I do not have a great deal of experience with an Overdrive. Is it worth going after this?

 

[RootesRacer]

all series alpine complete overdrive transmissions will fit all years with a few caveats.
Early alpines used a 10 spline input shaft and 10 spline output shafts.
Late alpines used 25 spline input shafts and 10 spline output shafts.
The some of the latest alpines used 25 spline input shafts and 25 spline output shafts.

This makes things interesting from a driveshaft and clutch disc standpoint but nothing is unsolvable.

The overdrive unit itself is generally interchangeable onto all series OD specific alpine transmissions, but there is the 25 spline output shaft
possibility to consider.

Earlier OD units may or may not have a factory modification to fit a pressure balance hose to prevent oil loss and OD failure.

Later OD transmissions (allsync models) has this equivalent feature without the need for the hose since the OD to trans adapter has a port for this purpose.

SIII OD units will have a special speedo gear compared to all others due to its 3.89 final drive ratio, but this is not a huge problem IMO.


As for is it worth it? If the OD and trans are known good units, the drop in revs is great.
If either is questionable you risk a lot of effort for more R&R.

 

[Bill Blue]

Is it worth it? A lot depends on what you expect of the O.D. If you expect to tear around the countryside, upshifting and downshifting willy-nilly, the answer is no. You will have a ball and a junk overdrive. My first Alpine "back in the day" had overdrive. I was told by the dealer that I could drive it anyway I liked, it was designed to "take it". It is not and needs to be driven in a manner that reflects its shortcomings. I'm not so sure that anybody knows exactly what that is. Now, as an old man, the appeal of the O.D. is gone, probably never to return.

Bill

 

[Ashfried]

If you don't drive on highways or freeways much, OD is not needed, but if you do, it is great. My SV had non working overdrive when I got it, and I loved driving it, but on a 1000 mile 3 day weekend it got old fast. I fixed the OD and the next long drive weekend was like night and day. No more need to stay in right lane and being happy to be behind a slow truck to keep it under 4000 RPM, now it is center lanes all weekend long.

 

[65beam]

OD units are interchangeable if you have the proper length out put shaft with the cam lobe on it. You can't install the OD to a trans that was originally a non OD unit without the right out put shaft.

 

[Tom H]

Andrew, It seems to me from your post that you are considering adding an OD box to your existing transmission. If that is true it's probably not worth doing. As 65Beam noted, adding an OD box to an existing tranny requires swapping in a correct output shaft inside the tranny. And finding a correct OD type output shaft for your existing tranny will be quite difficult.

On the other hand , swapping in a replacement tranny with OD on it is not difficult and surely worth it if you do much driving at modern highway speeds. Note that your speedometer will be inaccurate unless you swap in a new speedo or have it modified, or buy an adapter box.

Tom

 

[beamdream]

What 65beam & Tom said, having the OD unit is one thing, finding an OD type output shaft to put into your existing gearbox is quite another.

Certainly there are other problems to overcome, speedo, tailshaft, spline sizes etc. but you must have access to a short out put shaft to go into your gearbox before fitting the OD unit, finding one of them is not so easy.

 

[Alpine 1789]

If Tom is correct, that does change things. But assuming Andrew has access to a full OD transmission, I will add that I consider putting in the OD to be the single best improvement I have made to my SV in more than 40 years of ownership. It is not just for highway use, although it totally changes the character of the car for the better on the highway. I frequently find cruising back roads in 3rd gear with the OD to be the perfect combination. You have to either downshift or cut out the OD to accelerate, but the OD really does give you a 6-speed transmission and sometimes the 3rd gear OD just hits that sweet spot between 3rd and 4th. I would never own a stock engine car without one.

 

[Andrew]

A number of things have changed for my car. Back in 2008 the original S3 trans was swapped out with a S5. Thinking now, I wish I would have just rebuilt the S3 trans and keep it original.

I have a SII full overdrive trans, switch etc. but I do not have the drive/prop shaft. I do a good amount of freeway driving and that is what eventually caused my original engine to require rebuilding. I was not nice to the engine travelling at higher speeds back and forth from the Invasion in 2007 & 2008.

I would like to make the change but it may not be possible with miss matched splines etc.

Thanks for the insight.

 

[Alpine 1789]

Early alpines used a 10 spline input shaft and 10 spline output shafts.
Late alpines used 25 spline input shafts and 10 spline output shafts.
The some of the latest alpines used 25 spline input shafts and 25 spline output shafts.

I don't think you will have a problem with the splines. I am pretty sure that "Late Alpines" with 25 spline input shafts was limited to the last run of SV's. Your car and your transmission should both have 10 splines in and out. And, cutting down the prop shaft is no big deal. Google "drive shaft specialist near me". All you have to do is install the new transmission, measure the new prop shaft distance and take it a specialist. A few days later you will have a newly cut down and balanced shaft. It was quite a while ago for me, but I think it cost me less than $100.

 

[sunalp]

It was quite a while ago for me, but I think it cost me less than $100.

The last one I did, which was two years ago was a little bit over $200. Inflation?

 

[65beam]

I don't think you will have a problem with the splines. I am pretty sure that "Late Alpines" with 25 spline input shafts was limited to the last run of SV's. Your car and your transmission should both have 10 splines in and out. And, cutting down the prop shaft is no big deal. Google "drive shaft specialist near me". All you have to do is install the new transmission, measure the new prop shaft distance and take it a specialist. A few days later you will have a newly cut down and balanced shaft. It was quite a while ago for me, but I think it cost me less than $100.

There was roughly 1831 series 5 with the fine spline so odds are pretty slim that he has one.

 

[ALC 68A]

As has been said, the best option is to find a gearbox with overdrive unit complete. It is possible to strip a non O/D box and swap the main shaft for the longer O/D one and there is someone in the UK club that offers this service. I don't know whether there is anyone in the USA who does though.

However, you do need a bit more than the gearbox and overdrive unit. You also need the steering column switch, the relay from under the bonnet, the associated wiring loom and the dashboard warning light. Non O/D cars also had a 3.89:1 differential, whereas O/D cars were 4.22:1 (except S3, which had the 3.89:1 for some reason). All that being said, if you can assemble all the parts, it is worth converting for reasons of driveability and petrol economy.

O/D cars are fairly common in the UK and I've often wondered why so few Alpines were sold with it in the USA, bearing in mind the longer travel distances compared with over here.

Steve G

 

[Alpine 1789]

O/D cars are fairly common in the UK and I've often wondered why so few Alpines were sold with it in the USA, bearing in mind the longer travel distances compared with over here.

I have often wondered the same thing!

 

[Bill Blue]

Just a bad decision and we have to leave it there.

I once had a conversation with a newly installed upper level management guy. He was an EE, who, fresh out of college, got into solid waste. As a newbie low level administrator he had sit in on meetings and watch decisions being made, often wondering what information they were privy to that he was unaware of, as some decisions made no sense to him. But after a few years, he decided no, they knew less about issues than he did. They simply were making bad decisions. Sometimes due to bad or incomplete information, sometimes due to stupidity.

I have no idea how such a guy got to be elevated to a top level position, but it was a good thing.

Bill

 

[65beam]

Here in the states the distribution network was set up with master dealer distributors supplying dealers. East coast cars were shipped to a dock warehouse and were generic cars since most of them were intended for these master distributors to sell to their sub dealers. Most options were dealer added unless the car was special ordered. Long time TE/AE member Dan Morris that hauled and delivered the cars to dealers from the Newark and Jacksonville warehouses told many of us about this as did Wally Swift.

 

[Andrew]

As has been said, the best option is to find a gearbox with overdrive unit complete. It is possible to strip a non O/D box and swap the main shaft for the longer O/D one and there is someone in the UK club that offers this service. I don't know whether there is anyone in the USA who does though.

However, you do need a bit more than the gearbox and overdrive unit. You also need the steering column switch, the relay from under the bonnet, the associated wiring loom and the dashboard warning light. Non O/D cars also had a 3.89:1 differential, whereas O/D cars were 4.22:1 (except S3, which had the 3.89:1 for some reason). All that being said, if you can assemble all the parts, it is worth converting for reasons of driveability and petrol economy.

O/D cars are fairly common in the UK and I've often wondered why so few Alpines were sold with it in the USA, bearing in mind the longer travel distances compared with over here.

Steve G

Well, I have steering column switch, the relay from under the bonnet and the dashboard warning light. I don’t have the associated wiring loom and drive shaft. I have a SV trans with S3 Diff gears and love to give it a go if it would make the car more usable.
Any help would be appreciated but I find myself to confused now as there seems to be too many variables?

 

[alpine_64]

Andrew, to clarify... The OD you havr access to.. Is it
1. Just a Dtype laycock OD unit alone.
2. A Dtype OD unit and the adaptor plate to fit to a rootes gearbox
3. A Dtype OD unit and the adaptor plate to fit to a rootes gearbox and the mainshaft to go into thr gearbox.
4. A full rootes OD gearbox.

Firstly lots of cars used the Dtype OD ( volvo, triumph, bmc etc).. But there are several % ratios so careful which one it is if its just an OD unit and not sure what car its from.

If you dont have the mainshaft that goes from the OD unit into the gearbox... You are short a major component.

Also... Be careful of the OD mainshafts... The full synco box ones were susceptible to twisting with hard use which is why od boxes were sometimes removed from a car

 

[beamdream]

A number of things have changed for my car. Back in 2008 the original S3 trans was swapped out with a S5. Thinking now, I wish I would have just rebuilt the S3 trans and keep it original.

I have a SII full overdrive trans, switch etc. but I do not have the drive/prop shaft. I do a good amount of freeway driving and that is what eventually caused my original engine to require rebuilding. I was not nice to the engine travelling at higher speeds back and forth from the Invasion in 2007 & 2008.

I would like to make the change but it may not be possible with miss matched splines etc.

Thanks for the insight.

Well perhaps this is your best option, swap out the S5 trans for your S2 and shorten your tailshaft, as others have said this is not a big deal, the fact that you have the electrics makes it pretty straightforward.

 

[Andrew]

Andrew, to clarify... The OD you havr access to.. Is it
1. Just a Dtype laycock OD unit alone.
2. A Dtype OD unit and the adaptor plate to fit to a rootes gearbox
3. A Dtype OD unit and the adaptor plate to fit to a rootes gearbox and the mainshaft to go into thr gearbox.
4. A full rootes OD gearbox.

Firstly lots of cars used the Dtype OD ( volvo, triumph, bmc etc).. But there are several % ratios so careful which one it is if its just an OD unit and not sure what car its from.

If you dont have the mainshaft that goes from the OD unit into the gearbox... You are short a major component.

Also... Be careful of the OD mainshafts... The full synco box ones were susceptible to twisting with hard use which is why od boxes were sometimes removed from a car

No, I have a complete SII trans with OD, switch, relay (missing the wiring and drive shaft only).
In the car at this time is a S5 Trans and a S3 Diff.

I wonder if the SII Trans is as good as the S5?? I thought I might be able to use the S5 with the OD but it sounds like a complete swap would be best. Please tell me your thoughts.

Thanks,
Andrew