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 

[owensparrow]

Hmmmm, pretty sure I’ve got no pressure, and I can’t remember seeing the cam on the main shaft,so it looks like the overdrive is going to have to come back out. Can I do this without taking the whole gearbox and bell housing out, I think I might have an enthusiasm failure, if I’ve got to take all those bellhousing bolts out again?

[Pete Lewis]

yes you need to lift the od quite high , check rad hoses etc. when doing this 

refit can be a fiddle if you have a dummy mainshaft to align the splines it helps

if there is room with a pair of levers prise the piston plates open as this will release the cone clutc and it all self aligns 

you need an extra pair of hands to do this,  we managed on the Vit6 it was not easy but can be done on the car 

getting it over  the prop tunnel and handbrake may cause obstruction  , comes off easier than gong back on 

decent tea bags is a must 

Pete

[owensparrow]

That’s what I’d hoped you’d say. Thanks Pete, I’ll tackle it next week and tell you how it goes. 

[owensparrow]

I can get the overdrive on to within an inch of home, but I can’t get it all the way, I’ve done all the usual wriggling and gentle tapping, but she just won’t go the last little bit, the cam is set up to the top ( out of the way as it can be) it seems to locate on the shaft ok, any ideas before I scrap the whole car? 

[owensparrow]

It’s OK! On the 104th attempt it gave in and clunked together. Happy days! 

[Pete Lewis]

but does it work ok now ???

Pete

[johny]

Yes what did you find to explain it not working before? Also were the reverse idler and 1st gears ok?

[owensparrow]

It works perfectly! Really chuffed. The problem was the cam that pumps the overdrive unit ( on the gearbox main shaft) wasn’t fitted, the guys that supplied the overhauled box didn’t fit it for some reason, don’t understand why, and I didn’t notice it wasn’t there. The rest of the ‘box is fine.

incidentally I had to go for an overhauled box as I couldn’t find the parts to do my own, which I’d have preferred, there are lots of “suppliers” out there who claim to be able to source bits , and keep you hanging on for weeks, then can’t get hold of them, this whole episode took 3 months. Next time I get this sort of problem I’ll get a second hand unit and sort it out before I start pulling my car to pieces. 
Thanks again to everyone for their help , it was invaluable.

[68vitesse]

My first port of call, for gearbox, from previous experience would be Mike Papworth.

Regards

Paul.

[JohnD]

Whose workshop, I am told, is temporarily closed.

 

 

 

Edited May 21 by JohnD

[Pete Lewis]

2 hours ago, owensparrow said:

It works perfectly! R

its normal that an exchange box does no have the OD anciliaries are not fitted 

one other thing (too late now its refitted is the anti rattle flat circlip sits in a groove it the OD extended mainshaft

its not essential, many i guess are missing but can reduce gear chatter from the hub .

Pete

[owensparrow]

I was wandering what that clip did, it was missing on the overhauled box, if I’d thought about it I should have changed it over. I got my overhauled gearbox from Quiller and I’m very happy with it.