Spitfire Advice on swapping to J Type OD with 1500 engine in 69 Spitfire

[Bruce100]

Hi all,

I picked up a J Type OD (PO says worked fine), mounting plate, and shorter driveshaft recently to install in my Spitfire - note that it has a 1500 engine in it now. J type Any recommendations? Current plan is to install new U Joints, change oil in Transmission. Since I don't know what oil was used in the OD, I was thinking of changing the oil, cleaning the Sump Filter and Pressure Filter per Haynes. Also going to inspect clutch and replace as needed.

Never had an OD before so any advice appreciated.

 

[TR3driver]

Did you get just the OD, or a complete transmission with OD already installed? Either way, my preference would be to check the operating pressure before installing, as that will tell you a lot about the condition of the unit. I've seen a lot of "working when removed" overdrives that were sick and in need of major attention.

If you got just the overdrive, then there is a lot more work involved. You'll need to tear down the transmission to change to the OD mainshaft, etc.

 

[Bruce100]

transmission and overdrive

 

[TR3driver]

Should be fairly straightforward, then.

I'm not familiar with the Spitfire Haynes; does it mention that you need a special tool to remove the high pressure screen? Unless the suction filter is crudded up, I might leave the other alone. I built a tool that got the job done, but it wasn't entirely satisfactory. The plugs are only supposed to be tightened to 16 ftlb, but mine were much tighter. My tool is a heavy steel bar, maybe 5/16" thick, with two holes drilled and reamed to match the holes in the plug then hardened pins pressed into the holes. It was plenty strong enough, just not enough room to swing it under the car. Next time I'll make something closer to the factory tool.

Don't skip hooking up the lockout switch, it's kind of important. Not such a big deal if you forget and leave the OD on in 1st or 2nd; but leaving it on in reverse can lead to expensive damage. The lockout switch is what ensures that doesn't happen.

 

[Andrew Mace]

OD aside, which gearbox (three-rail or single-rail) is coming out, and which is going in? Clutch driven plates differ between the two, due to differing input splines.

 

[Bruce100]

three rail is coming out, single rail going in. I guess I need to buy a new clutch too!

 

[Bruce100]

So looking at clutch - are the Borg Beck clutches still subject to the problems of being too stiff as discussed here - https://www.vtr.org/maintain/clutch-laycock.shtml ?

 

[Andrew Mace]

I've never known there to be that sort of problem with Borg & Beck clutches in Spitfires, no!

 

[Trevor Triumph]

Twice I've replaced the three rail transmission with the single rail and OD to a earlier Spitfire. I had to replace the fly wheel. I think Spitbits or Rimmer Bros had bolts and a set of bushings to bolt the proper flywheel to the crankshaft. I was surprised that the guys at Roadster Factory had no idea how the connect the 1147, 1296, and 1493 in the MKIV to a single rail transmission. A friend pointed out that TRF may be more interested in proper restorations rather than the modification.

 

[Don_R]

The flywheel problem is with the 1147 and small bearing 1296..

The Big bearing 1296 and 1493 can use the same flywheel......the essentially have the same crankshaft...

 

[Bruce100]

So this weekend I am going to:
1. Open the top of the gearbox to make sure reverse gear is ok, other gears
2. Install new U Joints on the shorter prop shaft
3. Check flange on prop shaft to see if it fits the differential
4. Remove existing transmission and measure clutch disc to validate size, flywheel,, which clutch to order
5. Check other clutch components beyond disc, plate, throw out bearing
6. Order all clutch parts
7. Check solenoid, wiring diagram, order new switch/plastic cover for gear knob

I'll keep you all posted - thanks for the help!

 

[Bruce100]

So I opened the top cover of the gear box. all the gears and syncros look new! Except reverse. It has a strange pattern on the gear. a fine line running up the middle of each tooth. What do you all think? What else should I be looking for? What else should I refresh while I have it this far?''

 

[Trevor Triumph]

Odd, I had a 1493 connected to a three rail transmission apparently on of the earlier engine/ trans. combination. The engine was in a MKII car, but I think early, 1974 cars had that combination.

 

[Don_R]

I have a 73 Spit...part MK4 part 1500....sold as a 1500 here in the States....made Oct of 72

Engine trans combo is Big bearing 1300 (its not an FM motor) with the 3 rail trans...

The clutch is its own beast...7 1/4" with a 10 spline center......the small bearing motor used a 6 1/2 " 10 spline

the later cars, used a 7 1/4" 20 spline clutch