New gearbox now O/D won’t work

[owensparrow]

I’ve just fitted a re conditioned gearbox to my late model GT6 and now my overdrive won’t work. The big worry is that when I dismantled the gearbox from the D type O/D there was a cam, or a slightly off center spacer on the bench covered in oil that must have come out of the overdrive, but I couldn’t find where it had come from. No mention of it in the Haynes or any exploded view. When I picked up the new gearbox they couldn’t identify the part, and I couldn’t fit it on any shaft, it was just too small ( it’s about 30mm outside diameter) 

Could this be why my O/D isn’t working? I’ve got a click from the relay, and the oil level is good, any ideas? I’ll try to post a pic of it.

[owensparrow]

Here’s the part I’m worried about. 
incidentally, when I refitted the overdrive to the gearbox, I followed Haynes instructions to just push the two together, they clunked together nicely after a bit of wriggling, I didn’t synchronise anything, was that bad? 

[JohnD]

Ooooh! "Bits-left-over-after-rebuilding-grandfather-clock" syndrome!  Never a good sign!

The only single 'cam' in an OD gearbox that I can think of is the eccentric on the front of the main shaft, that drives the pump to pressurise the operation of the O/d, so if that's missing, then no pressure, no operation.

My copy of the Official Workshop Manual has a test procedure for the pump, Page 2.305, "Functional Check".   The usual exploded diagram of the O/d  omits the "front of the main shaft" and this cam, but again the OWSM has pictures on pge2.307.

Also, my Haynes manual for the Spitfire has a diagram that includes what looks like the part you show, No.1, "operating piston"     meaning operating cam, I think.

Scans below.

JOhn

 

Edited April 23 by JohnD

[Colin Lindsay]

That part looks like a spigot bush / spigot bearing from the input shaft / flywheel end of crank? 

[Pete Lewis]

a steel spacer its likely from the reverse shaft 

if you fit the OD and dont turn the cam to its lowest point the pump roller assy can get bent 

its best to drop the pump , the cam has achamfer to lead the roller on but it can cause troubles 

most failures on a recent refit is down to the cam woodruff key has been left out .

pete

Edited April 23 by Pete Lewis

[johny]

2 hours ago, owensparrow said:

Here’s the part I’m worried about. 
incidentally, when I refitted the overdrive to the gearbox, I followed Haynes instructions to just push the two together, they clunked together nicely after a bit of wriggling, I didn’t synchronise anything, was that bad? 

Yes as said it is entirely possible for them to go back together with no other actions necessary (cam in right place and splines already synchronised) so maybe you were just lucky.

Also as Pete says the steel spacer looks like part number 8 which would fall off the end of the reverse spindle very easily. Its important as it prevents the reverse idler gear from going too far backwards and clashing with the 1st gear cog. However I cant see why this would prevent your OD from working so the next step would be to verify the operation of its solenoid...

[owensparrow]

Aaaha! Jonny, you might have something there, my reverse gear WAS going out of position and hitting something so had to be replaced, so it looks like it came from the gearbox and not from the overdrive ( I separated the bell-housing and O/D from the gearbox all at once , then noticed that part on the bench) 

Thats excellent news, I will search elsewhere for the reason my overdrive isn’t working, possibly I’ve messed up the wiring.

Thank you so much chaps.

[DanMi]

to tell if it is wiring just put the car into 3/4 flick the OD switch and listen for a load click from the right side of the box, i.e. the solenoid if the cover is off you can put your hand on it to feel it energise check that it is adjusted properly so that the holes align when energised 1/8" drill bit. Also check the oil level. All simple things to do before deciding to take the box out

[owensparrow]

Still no overdrive and the solenoid is definitely working, although I haven’t checked the throw. 
Pete, thanks for your input, as always! Is it possible I’ve bent or even snapped off the pump roller when I put them together, have you ever heard of that? 
Any other ideas?

Anything I could try before I rip it all out again? 

[Pete Lewis]

if you remove the cap from the top of the operating needle and run at 20mph you should get a good squirt of oil , there is a test proceedure 540/560 psi from that port .

if you get a squirt  remove the ball and spring  and withdraw the needle/spool  it has a small hole through its centre  it must be clear they do get blocked 

have you cleaned the filter and magnetic rings inside the plate opposite side of the solenoid/lever cover ???

Pete

[owensparrow]

Hi Pete, I’ll look out for the port and take the cap off it, that will be a good test, I think my mate has got a pressure tester I could screw on. That’s great gen, thanks very much.

[micklewis]

On 02/05/2024 at 10:02, owensparrow said:

Hi Pete, I’ll look out for the port and take the cap off it, that will be a good test, I think my mate has got a pressure tester I could screw on. That’s great gen, thanks very much.

when pressure testing you need a dummy cap  the spring and ball under it has to be in the correct position  or you wont get any pressure reading , its done a 20mph too 

 

mick