Differential overhaul

[rogerguzzi]

Hello All

             I was thinking of overhauling my differential Spitfire 1500

 

Now I can get the bearings and seals ok  but where do you get the planet wheel shims from? All suppliers say NLA.

 

I can not believe there are non left when they made so many units.

 

So how do these firms offer rebuilt units?

 

Perhaps the club could get them remade?

 

Or has one of you clever people made some? After all its just some phosphor bronze sheet pressed into a curve(I think) now where can I get some sheet in different thickness's and make a simple press tool to use on my 8 ton hydraulic press?

 

Roger 

[Pete Lewis]

Other makes with similar design may have a compatible or easy modifiable speherical washer you can use

pete

[Pete Lewis]

http://www.mgocspares.co.uk/acatalog/MGOC_SPARES_AXLE___BANJO__MGB__123.html

Item 32 1G7445 as an idea

 

pete

[rogerguzzi]

Hello Pete

                 That's a good thought, I can not be the only one with this problem?

Morris minor's and midgets have similar looking washers.

 

Does anyone have some old ones to get the dimensions off?

 

Roger

[Pete Lewis]

Wear on the spherical thrusts is not problematic unless they are total wreck

 

as backlash on the planets and sun gears is not a driving problem

puts a it of extra rotation from drive to coast , but they only turn creep slowly on corners, they only spin to destruction wiith one wheel spin on ice and rev the nuts then grab some grip that shock load can break teeth/ gears or the short output shafts

Pete

[rogerguzzi]

Hello Pete

                I have been thinking about my differential again(sad I know)

 

You can get the sun wheel shims from moss, so could I not fit slightly thicker ones to take up wear in planet wheel shims?

 

Plus why do I have to fit a collapsible spacer? surly this was fitted just to speed up assembly instead of fitting shims to get the pre load on the bearings? I could make one in my lathe to the correct length!  

 

Roger 

[Pete Lewis]

yes collapsible is just a cheap production compromise  youre right.

 

so long as you have some  specified pre load on the pinion bearings , this always keeps the pinion in the same place for drive or coast 

 

as for thicker sun or planet thrusts all is possible just dont remove all play as they are crude teeth and need to have space for lubrication.

 

free play wont affect noise they dont turn much , it will make some play between 1 halfshaft and  the prop coupling but thats not an issue 

 

if you stand the pinion on its  drive thrust bearing you can measure the height to the tip of the gear and if you replicate this with the new bearings then the mounting  distance (mesh)  with the crown wheel wont be affected it will assemble same as whats come out

 

Pete

[rogerguzzi]

Hello Pete

                 That's what I thought and they tell you the torque figure needed in the workshop manual for the turning resistance minus oil seal so that's what I will aim at.(that's what I did on my brother in laws TR6)

 

Never did like the thought of a collapsible spacer! especially it you have to change the nose seal.  

 

I have the diff out and on the bench now I may remove it from the casing later and have a look and see if I can measure washers etc. before stripping it down.

 

Roger

[Pete Lewis]

Good luck,

 

always check crown wheel back lash with dia indicator at right angles to the tooth flank

or you dont get the correct dimension if the stylus rams up the tooth face rather than its rotational

clearance,

 

the figures on the end of the pinion are in thous of inch away from the height of the projected cone of the pinion where it meets the centre line of the crown wheel to give its best running position

 

so if you can copy the removed ppinion height it saves using a lot of metrology and mandrils

if the bearings stack tomthe same heights is a saviour

pete

[rogerguzzi]

Hello Pete

                I think I am having a bad day?

 

I am trying to set the pinon preload with shims as was the old method(when I looked and stripped my differential I found it was a Vitesse one but with the 3.63 crown wheel)

I have adjusted the shims to get rid of the play and at 90lbs/ft on the nut I get about a 12oz weight on a 12" strip(24" really to balance) before it turns.

 

But according to the workshop manual it should be 13 - 20 in/lbs(Spitfire seal fitted) 12-16in/lbs(vitesse no seal) 15-18in/lbs(TR's all no seal)

 

So according to my reckoning I am only half way there but it feels tight(ish) to me.

 

So do I take another 1-2 thou shim out and make it tighter?

 

Roger

[Pete Lewis]

Try with a smaller shim but it may take it too high

 

 

your not far off so far, and oiled bearings can lower the pre load torque vs dry brgs.

apart from the spec was revised for some reason there is no lodgic why a spit or vitesse diff is different

 

seal or no seal is obvious but the tollerance variation has no real model related offering apart from

collapsible vs shims

 

more strong tea required

 

pete

[rogerguzzi]

Hello Pete

                Perhaps a shot whisky in my tea?

There is no real rush as the club have run out of the rear diff mounting bush and I am having a new prop shaft made at Proptech with a uj at both ends and sliding joint plus he said he will fit stronger uj,s?(should see me out?)

 

Roger

[rogerguzzi]

Hello All 

             Well its back together!!!

 

The best I could get the crown wheel and pinion mesh was 3 to 6 thou.

 

There is quite a lot of play on the output shaft splines to sun wheels but the rest feels ok?

 

I tried bluing the teeth and it looked ok ish.

 

Well time will tell or I may be looking for a new differential?

 

Roger

[Pete Lewis]

Well you have tackled what many shouldnt, couldnt, or didnt

 

let us all know how she sounds

 

pete

[hugh]

For the curved thrust shims try landrover lt230 transfer box centre diff shims did us proud on our 1500 diff, only available in one size but !!!! Anything is better than paper thin or missing