Spitfire gearbox overhaul

[Jonah]

I’ll try that Johny, I loosened the mounting bolts and just supported the engine on a jack to give me some wriggle room

Should I remove the mounting bolts completely to do this?

julian 

[Pete Lewis]

i have never had to loosen engine mounts   

exhaust  yes  maybe cooling hoses if you are going to stretch them 

but its surprising how high you can lift the rear end to match the geabox insert angle 

if you let the front mounts lift you dont gain angle 

Pete

[Paul H]

1 hour ago, Pete Lewis said:

i have never had to loosen engine mounts   

exhaust  yes  maybe cooling hoses if you are going to stretch them 

but its surprising how high you can lift the rear end to match the geabox insert angle 

if you let the front mounts lift you dont gain angle 

Pete

From my limited experience with my overdrive box going back into my Vitesse I had similar difficulties . Firstly I hadn’t raised the gearbox high enough though the PO had the locating studs in place . Using a torch looking in from the engine side that the gearbox was parallel to the engine plate . Hope this helps . I also used stout timber either side of the box to provide leverage to get parallel . 
Paul

[Jonah]

Thanks Paul

i think that was my problem as well, i hadn’t  raised the gearbox or the rear of the engine enough, I was a bit timid about jacking up the engine 

hopefully tomorrow will bring success!

Julian

[johny]

I dont want to throw a spanner in the works at this late stage but I take it the clutch friction plate has been checked for wear and the same for the crank to gearbox input shaft bush? 

[Jonah]

No they haven’t been checked………but they will be now!

thanks Johny

[johny]

ok so if you dismantle the clutch you'll need something to recentralise the plate (either the original or a replacement) when you reassemble it. Then I thought the bush could be hooked out of the hole in the centre of the flywheel but not sure now that it can removed with the flywheel in place and maybe you dont want to go as far as that....

[Paul H]

I used the opportunity of changing the clutch and clutch release bearing . 
Paul 

[Jonah]

I changed the clutch release bearing as part of the gearbox rebuild but haven’t changed the clutch…….yet!

[Paul H]

22 minutes ago, Jonah said:

I changed the clutch release bearing as part of the gearbox rebuild but haven’t changed the clutch…….yet!

For the cost involved I changed the clutch as I didn’t know how long it had been there . At £68 from Canleys it was an easy decision . Replacing worked as the “budgie singing “ has gone . I also removed the fulcrum pin replaced with a washer which changed the angle and compensated for wear. I’m sure Pete Lewis who mentored me on this project will be along to explain 

Paul 

[Jonah]

Thanks Paul

i replaced the fulcrum pin, the insert and the fulcrum bushes as I could see wear on the bell housing….. but hadn't changed the clutch plate

[GrahamB]

I am having similar problems with my Spitfire overdrive box after replacing a slipping clutch.  I had to disconnect the propshaft at the diff,  as without a sliding joint, you cannot push the gearbox end of the shaft back to get any clearance.  I have fitted longer studs but when trying to refit the box, there is a small gap at the top and a large gap at the bottom.  The problem appears to be that the filter unit on the overdrive fouls the mounting plate for the rear of the gearbox; it is as though the instructions in the WSM are for a box without the overdrive unit. I have tried jacking up the rear of the engine but all that happens is that the whole car rises off the front axle stands!  It is though the engine mounts have hardened with age and will not allow any movement. The next plan is to remove the mounting plate  so I can lower the end of the gearbox and to loosen the front engine mounts so the engine tips rather than raising the whole car.  It does not help that I am now not as strong as I was 10 years ago!

[Jonah]

I feel your pain, that’s  sounds terribly familiar Graham. I removed the overdrive mounting but haven’t removed the mounting plate so that’s now on tomorrow’s list 

did disconnecting the prop at the diff give you the clearance you needed?

[johny]

7 hours ago, GrahamB said:

I have tried jacking up the rear of the engine but all that happens is that the whole car rises off the front axle stands!  It is though the engine mounts have hardened with age and will not allow any movement.

This is very strange as the engine mounts on the Spitfire are right at the front of the engine so jacking at the rear of it should tilt it not lift the whole thing. Ive used a thin but wide piece of wood fitted between the backplate and sump to jack on before to ensure the push is applied as far back as possible.

Obviously once the gearbox is mated get it supported with wood as soon as possible while you do up some bell house bolts. Then its best to have a assistant gently release the engine jack while you lower the gearbox into the correct position...

[Pete Lewis]

i have a wooden block engine lifts the block by fitting up between end of sump and backplate 

agree with the forward spit/ herald mounts you are  lifting far towards the front it needs to be much towards the back of the sump 

lift the engine high  just watch fan and hoses   taking some engine weight off the springs will allow the car to rise a bit 

but you do need to raise the backend with the front firmly attached more than you think 

Pete

[Jonah]

Pete, you mentioned earlier a possibility of my prop being telescopic. Looking at the Rimmer catalogue it looks like my Mk3 with overdrive should be telescopic. I’ve assumed that mine isn’t because it doesn’t seem to slide but is there a better way to properly test my assumption?

julian 

[Pete Lewis]

yes get under and look at it  , not important which end its fitted , but generally at the diff end so you access its greaser

heres a pic of a prop + telescope from J paddock  mkIII  there are fixed props and the nasty strap drives  neither of these two will allow any shift in length 

[Jonah]

Should mine be a telescopic version in the Mk3?

[Jonah]

It is a telescopic prop with the joint at the overdrive end

should I be able to push the joint back?

Julian

[NonMember]

I think all Spitfires should have a telescopic prop, apart from maybe some very late 1500s that got a CV type.

The fixed and and strap type propshafts were fitted to Heralds.

You should be able to compress and expand the prop a little, but it may need a bit of effort as the telescopic joint may have got a bit sticky

Edited March 26, 2023 by NonMember

[Jonah]

Thank you, yes it moved a little after some persuasion but not much

[johny]

get some WD40 or similar sprayed up inside the splines and free it off...

[Pete Lewis]

if part seized. it probably due to never been greased  hence why most have the tele at the back .

if the telescope is backed up and appears close to the tube end then its fully   compressed 

wsm quotes 0,5" extension to a BRD prop so there is not much to play with   where as the 1600 is 1.68"  

why the spit has so small slide i dont know 

Pete

[Jonah]

Hallelujah it’s in!

my engine crane gave me the ability to raise the back the engine enough and after lubricating the prop shaft telescope it moved enough to get the flanges to meet

A few more bolts and tidying up then it should be ready for a test drive this week and fingers crossed it goes well

thanks everyone

Julian

[Jonah]

Test drive update

today was the day, a very short drive to test the gearbox, gear selection is sharper but second really takes some effort to engage, when it does it’s fine with no crunch! Should I be concerned about this?

not sure about the overdrive yet

julian