View Full Version : Spitfire Spitfire - Single-Rail Gearbox Frustration !!!

11-09-2008, 05:47 PM
Please excuse the tone of this post. I'm currently very, very angry. I have no one to blame but myself for today's events. I'm not angry at anyone here. However, I would like feedback from any and all with experience regarding the below.

The story so far is, we bought a '72 Spitfire non-running project car. Once I got it marginally operational I took it around the block only to discover the gearbox had bad syncrhos on 2nd and 3rd. A friend of mine gave me a known-good single-rail box to replace the 3-rail in the car. He said "it will bolt right in".

Subsequently I have learned that it will NOT bolt right in and I needed a new driveshaft, new speedo cable, and a new "clutch" (because the input of the single rail box has 20 splines instead of 10).

So, I got a used driveshaft, I ordered a clutch disk and speedo cable. Today was the day. My son and I pulled the old gearbox and clutch out and I told him we were going to dry-fit the clutch to make sure it all fit. IT DOESN'T.

I was told by a couple of people that I would need the friction disk for a 1500 and that it would fit under the 1300's pressure plate. It doesn't. The 1500's disk is much bigger than the inside of the 1300's pressure plate. It looks like there is no way you could attach a 1500's pressure plate to a 1300's flywheel... the dowel pin spacing and bolt circle are too small.

So what do I need???? Do I need to buy the flywheel off a 1500? If I do buy a 1500 flywheel... will it bolt on directly or am I in for more surprises? Is there a smaller 20 spline friction disk I should have bought? What is the answer. I know these conversions have been done so I'm sure there are just a couple of things I haven't been told yet. I really don't want any more surprises. PLEASE, please, please... those of you who have converted from a 3-rail box to single... tell me what I'm supposed to do about the clutch components!

OK... so I moved on. I figured with the clutch issue on hold, I'd move on to cutting out and welding in the new battery box. I bought a replacement steel box from one of the usual sources (and trust me... I'll be discussing this with them). The replacement box did NOT have the back edge bent "upward" like the one in my Spitfire or our GT6. I figured... OK, I'll just bend it up prior to tack welding it in place. I continued to check things and found that the inner dimensions of the box were TOO SMALL to accept the plastic battery box liner I have. The liner fits the battery box in the car... this replacement steel box was about 1/4" smaller in both X & Y directions!!! I'm giving up on that and I'm going to glass it. I just hope the vendor will take the undersized box back AND perhaps pay for shipping. That vent is over... thanks for listening. Today was just NOT a good day for our project car and it's probably our last warm weekend.

Again... I beg any of you who have converted from 3-rail to single-rail gearboxes in a Spitfire, PLEASE recount your experiences and in particular, tell me which clutch components and/or flywheel I need. Your help and advice will be much appreciated!

Andrew Mace
11-09-2008, 06:18 PM
...I was told by a couple of people that I would need the friction disk for a 1500 and that it would fit under the 1300's pressure plate. It doesn't. The 1500's disk is much bigger than the inside of the 1300's pressure plate. It looks like there is no way you could attach a 1500's pressure plate to a 1300's flywheel... the dowel pin spacing and bolt circle are too small.

So what do I need????Doug, I suggest you call Ted Schumacher at TS Imported Automotive (https://tsimportedautomotive.com/). If I'm remembering correctly, there is a smaller diameter disc with the 20 splines from a home market Triumph Dolomite or 1300 or something along those lines. At any rate, I think Ted knows what it is and likely can supply or lead you to one. At any rate, there should be no need to change flywheels, etc., ... just the friction disc.

Oh, and if I might have been one of the folks who unintentionally misled you on this point, I sincerely apologize!

11-09-2008, 06:51 PM
No Andy, you were one of the people who directed me to the correct driveshaft. You have been very helpful. As I said, I have no malice towards anyone. I'm just frustrated at myself for not having all the information at the start.

I didn't realize I'd need Ted's help again so soon. I bought a set of Panasport lug nuts from him late in the summer. Fortunately his phone number is on the invoice. I don't remember seeing the phone number on his web site.

Thanks for the suggestion Andy.

Trevor Triumph
11-09-2008, 07:34 PM
I feel your pain... I was in Pennsylvania at the Roadster Factory and they were no help- I was surprised by that. I talked with Nigel owner of Spitbits. He was helpful when I replaced the three rail trnasmission in my 64 Spitfire. I used the 1147 engine mating it to the single rail transmission. Since I had the J overdrive I just bought a replacement drive shaft. I too was misled by people that said it was an easy change. I think the fly wheel amd clutch were replaced and I had to buy from Rimmer Brother sleeves that woul mate the 1147 carnk to the fly wheel. I mated a 1296 to the single rail as well. I don't think I had to use the sleeves for that swap. Since I have added the single rail to three cars that used a three rail gear box, the original 1147, the 1296 and an early 1500, I know I have several fly wheels and clutch sets in my parts inventory. The good part is, I'm told, the single rail is a better transmisson. Bottom line, it is work and one needs more parts. T.T.

11-09-2008, 08:36 PM
Trevor, if I understand you correctly, are you saying the later flywheel IS required? If so, I'm looking at a used flywheel and new pressure plate to go along with what I've already bought. This car has been such a joy.

Nothing can happen tonight anyway. I'll give Ted a call tomorrow. Maybe I'll get lucky and he'll know of an alternative disk. So far, all I've found on the web are 7/8x20 racing clutches that are either way too small, or the same size as that used on the later 1500.

11-09-2008, 09:14 PM
Having just completed that project in my own car, I replaced a three rail with a single rail o/d, here's what I found.

I replaced the flywheel, the 1500 flywheel is a two step design. You will need that to use the 1500 clutch. I personally don't know of any hybrid clutches, Ted at TSI or Nigel at Spitbits are your best bet there. I found a flywheel on ebay for 50 bucks to the door, and another 60 to machine it. I probably could have found a flywheel cheaper, but I didn't bother beating the bushes. The cost for the grinding was about average, took about 20 minutes while I waited.

If you replace the flywheel, you will need to make or have made spacers because the 1500 crank is threaded for larger bolts than the 1147 or 1300 uses. These spacers or tubes or sleeves or whatever you want to call them fill up the holes between the smaller 1300 bolts and the larger holes in the 1500 flywheel. I could have made step bolts and had them case hardened, but I don't think it was worth the bother.

I made my own spacers, as I have access to a machine shop, and made mine out of A36 steel, if that means anything to you.

Other than the different drive shaft everything else just bolts up.

While you're in there, do the slave cylinder throwout bearing and pilot bush.

Nothing is ever easy, is it?

11-09-2008, 09:16 PM
PS I also used socket head grade 8 socket head cap screws to hold the clutch to the flywheel, you will need 6, and get a couple extra. Be careful when torqueing these things in, your allen socket needs to be sharp and you need to apply a lot of pressure to keep these things from "camming" out.

11-09-2008, 09:52 PM
Thanks Steve. I've been cruising eBay and probably found the same deal on the flywheel that you did.

An annoying aspect of having to buy the 1500 parts is... I had already bought a new throw out bearing, pilot bush, and 1500 friction disk... one piece at a time. I thought I'd get out cheaper that way. Now... it looks like another $50-60 for a pressure plate plus another week+ waiting.

I don't use A36. That's a low carbon like 1018 isn't it? If so, I shouldn't have any problem making the bushings. Like you I have access to lathes and Mills. Since you used the bushings, was it necessary to use anything like heavy washers to straddle the larger holes in the flywheel?

Are the 1500's pressure plate bolts the same 5/16 UNF as the 1300? If so, I probably have a box of Unbrako socket heads around... if the length is right.

I'll be calling TSI and Spitbits tomorrow if time allows.

11-10-2008, 08:40 AM
No I didn't use a heavy washer, and yes the clutch bolts are the same size. The A36 is just what we have laying around our boiler shop, it's what we use as a general purpose type stuff.

Hopefully the length of your bolts is too long, a cutoff wheel and touch them to the grinder to finish the end fixes that.

I just finished making stainless brake pistons, and I have the program made for doing the slots in the rotors.

Hopefullly I will get the new burl dash done this winter.

Take pictures, I'd like to see how it's coming out for you.

11-10-2008, 09:18 AM
Wow Doug, and I thought I was having a frustrating time with my 3A tranny and o/d! I'm a piker compared to what your'e going through. I'm going to throw a name and number at you, it is Charles Vincent at Vinco Transmissions, He has been rebuilding British trannies and O/Ds since 1974. He is good people and might be able to help you out. He's in Jacksonville, FL 904-757-6300

Keep on plugging! Tinkerman

11-10-2008, 12:30 PM
Nigel at Spitbits had nothing nice to say about this conversion. He recommended that I fix the old gearbox and stick with the stock components. He went on to say that if I move forward with the single rail box I am looking at a new flywheel and pressure plate to complete the transition. He said there is no friction disk that has the 20 splines and 6-1/2" OD.

I guess I'll drain the 3-rail box and see what's inside.

I'll also call Ted at TSI and see if he knows of different options for me.

11-10-2008, 01:39 PM
And Ted says... 1500 flywheel and pressure plate along with the bushings to fit the larger bolt holes.

I'll have to stew on this for a while and see where I need to take my financial lumps.

11-10-2008, 02:57 PM
I pulled the trigger becuase of the price at which I got the o/d.

Less than 300 bucks to the door, right place, right time. When I got the top off, the synchro's looked almost new, and everything was nice and oily and smooth.

Read Paul Tegler's site, www.teglerizer.com (https://www.teglerizer.com), he has lots of experience with setting a three rail up. Seems a difference of a few thousandths of an inch makes all the difference in the world as far as shifting and the synchro's.

These little gearboxes aren't hard to rebuild. take the front and the rear off, and the front shaft slides out the front and the output out the back. new bearing synchro's and put the whole shebang back together.

You are right at the point of it's the same price to go either way.

11-10-2008, 05:30 PM
I'm sure this 3-rail box will be similar to the one in our GT6. I went through it years ago and set it up nice an tight. I was just hoping to not have to open up another gearbox.

I'm going to mull this over for a few days and decide what I want to do. If nothing else, I'll drain, clean, and open the three rail box for inspection.

11-10-2008, 05:53 PM
Come to think of it, I will have the 3 rail from my 71 that will be surplus, if you find peices in the bottom that are big enough to have part numbers on them.

11-10-2008, 07:15 PM
I haven't made a final decision yet but this is how I'm leaning.

I may go ahead and buy the pressure plate and flywheel for a later 1500. That will probably set me back over $100. I'll install the single-rail box and see how it goes.

I'll still have the 3-rail box and all the original parts to rebuild and re-fit at a later date if I choose to. I expect it will cost me... a bit over $100 to do a minor refresh of the 3-rail box and that will probably take more time than fitting the single-rail box I have ready to install.

You see... I've already invested in a bunch of parts. If I don't bite the bullet and spend a bit more, that first money will have been wasted. I'll let you know what I decide and how it goes.

11-11-2008, 10:12 AM
I'm pretty sure there are other clutch disks that would work, but getting the right one may be a lot more trouble and costly than getting the 1500 flywheel and pressure plate. I went through this when I put the single rail OD tranny in my Mk I. It was pretty much bolt in, but I had a parts car in the back yard with most of the necessary parts. I wasn't aware that the Mk IV flywheel used the larger bolts. The "bushings" you need are standard parts used in the differential to locate the bearing caps.

Personally, I like the shifting action of the three rail over the single rail. The single rail doesn't quite stick out the transmission cover in the right place in my MkI. I'm also not sure why people think the single rail is stronger. It could be, but I would like to now why. I have a spare three rail from a MkIV (that should be fully syncho) that I may put into my Mk I. Then I will put the OD trans into my 80 1500 car to make it a good raod car. The MkI may become a "race" car.

Andrew Mace
11-11-2008, 12:14 PM
... I'm also not sure why people think the single rail is stronger. It could be, but I would like to now why....Same here. Truth is, I don't think it's really much stronger <span style="font-style: italic">per se</span>; rather, I believe it was more a part of the "rationalisation" of parts amongst the various brands of BLMC. I don't know about all the little bits between the two boxes, but the ratios are identical between the MkIV/early 1500 three-rail and the later single-rail Spitfire boxes!

11-11-2008, 12:34 PM
The argument presented to me was the single-rail was stronger because it was designed to use some of the same parts used by the TR7. Since the TR7 had a more powerful engine, the logic was/is that the Spitfire box benefited from being "over-designed". This is all hearsay from me, put no faith in it.

Nigel at SpitBits specifically said he didn't like the single rail box for much the same reason that Andy mentioned. Nigel referred to the single-rail box as a sort of corporate design. He also added that he's seen more reverse gear failures in the single-rail box than he's seen in the 3-rail box. Since I spend most of my time going forward I don't know how much concern I have about that.

I told Ted at TSI that I had been searching for a 7/8x20 splined clutch to fit the pressure plate of the 1300. He categorically said I wouldn't find a street-able one. I mentioned I'd seen some that were smaller than what I needed and he immediately knew what I'd found... racing clutches. With no take-up springs on the disk, I'm not interested in trying those.

Either way I'm going to spend more money. I figure for now I'll buy the 1500 parts I lack and finish the transplant. At my leisure (when the car is completely roadworthy) I can take the 3-rail box apart and sort it out. I'll still have all the 1300 parts and can switch back at a future date if and when necessary. I need to move this project along by spring and have many other tasks to address.

11-11-2008, 01:12 PM
Another option, is to contact a clutch manufacturer.

If you know the sizing of the disk you need, width, thickness, height, splines, etc. Might contact a few people.

Reason, when I did my hvda conversion way back in the late 80's I lived in Fountain Valley, California. Went parts shopping. Talked to Bill Hays(Anyone remember Hays Clutches?) over at his shop Centerforce. After he sold the Hays clutch name to Mr. Gasket he got tired of being retired and got back into manufacturing. When I took him my specs and dimensions. He walked back and pulled out a disc and pressure plate. If I remember he said if was from the Ford Probe..

Now Bill has passed the company on to his son-in-law who has moved it to Arizona, something about saving on taxes. But there is another opportunity for you if it seems like you are hitting a brick wall. Centerforce may be able to help you if you contact someone high enough up the business ladder.

11-11-2008, 03:45 PM
When I was looking I was told that there are clutch companies that can put the Spitfire center on a smaller disk. It was just too easy to do it my way. I suspect it would be easier for you too. I may have an extra flywheel laying around, but it may not be for a 1500. I'll look if I can remember.

I may be about to get back in this situation again. I have a Ford Type 9 transmission that I am considering putting in one of the cars. It either needs a special clutch, or a standard clutch from some obscure car not sold in the US.