84 replies to this topic

[sibhs]

I'm about to undertake something I've done once before 25 years ago.

 

Rebuilding the M20.

 

I'll be asking many questions and putting up plenty of pics.

 

This is the four speed box that was with the car when purchased. Car had a three speed column in it and I'm converting to four on the floor.

 

 

Undo bolts and remove side plate.

 

Inside looks great, should just fill with oil and use it.

 

 

Next is loosen reverse nut and tap end slightly, undo bolts to extension housing and split.

 

 

A quick look at the reverse bits in ext. housing.

I found this chunk of metal stuck to the side, need to find where it's from. <

 

 

 

 

 

Looks like casing not gear related and the way it was stuck in some goo seems it had been there for a while.

Any guesses?

Edited by sibhs, 13 August 2014 - 10:03 AM.

[Shadow17]

Hi Marty I will be watching this one closely as I picked up an M21 and an M20 to go behind my motor and I want yo strip them both to see which one is best. Based on your current rebuild and attention to detail I am sure that this thread will be of great help to me

 

Thanks James

[Potta]

No idea mate but can you tell me if anything pops out or is difficult to put back in when you remove the bolt that holds the reverse switch?

 

I need to take mine off and I was going to attempt while it is in the car but I know it holds the detent ball and I'm worried something will fly out or fall off or something else will happen that forces me to remove the box and I really don't want to.

 

Sorry about the bit of a thread steal.

 

You know you can't just chuck some oil in and use that one, most people could but I don't think it would do the car justice to cut corners on something like that.

 

Looking forward to seeing this because I am hoping to get a cheap box to rebuild as a spare/replacement down the track and can refer back here.

 

Love your work mate.

[sibhs]

Hi James,

we'll both learn a bit from this thread. Hopefully I don't make too many mistakes for you to learn by :-)

 

Marty

[Mort]

Following with great interest.

 

I too want to rebuild a spare box and then the original if something goes wrong.

 

Don't forget, lots of pics and document any mistakes you make for us so we don't have to go through them.

 

If all goes well it should be made a sticky.

[Shadow17]

Marty based on how spot on the rest of your car is I know for sure that this thread will cover all the important facts and tricks and maybe any special "Marty Made" tools that made the job easier

[TerrA LX]

The look and shape and area where that piece was found looks like it is from the reverse arm/lever. the one that actuates the reverse idler gear.

[sibhs]

Knocked out the lay shaft using an old one that was shorter. (That's what it says in the book, I used a piece of shifter handle and a big screw driver) Roller bearings fall everywhere. Leave cluster in box but disengage gears.

 

 

These are the rings between roller bearing sets, book says six, I found five???

 

 

Remove main drive then cluster gear.

 

 

Tapped pin out so the reverse thingy could come out.

 

 

 

Found ya!

 

 

 

Is this a common break? Can they be bought new? I have a spare box I can check.

 

Lay shaft is worn.

 

 

Cluster looked good inside and out. Only this little mark, I think it's ok?

 

 

Need advice on what to replace. Here's my list that I know.

 

Overhaul kit which includes, bearings, seals, gaskets, cluster shaft, cluster shaft rollers, input shaft rollers, spacers, c-clips, keys, energizer springs, o-rings.

This kit is $92 inc delivery from J&VR Transmissions

 

Should I get  syncro's? Or anything else to check or recommend?

 

Marty

Edited by sibhs, 13 August 2014 - 10:48 AM.

[sibhs]

No idea mate but can you tell me if anything pops out or is difficult to put back in when you remove the bolt that holds the reverse switch?

 

I need to take mine off and I was going to attempt while it is in the car but I know it holds the detent ball and I'm worried something will fly out or fall off or something else will happen that forces me to remove the box and I really don't want to.

 

Sorry about the bit of a thread steal.

 

You know you can't just chuck some oil in and use that one, most people could but I don't think it would do the car justice to cut corners on something like that.

 

Looking forward to seeing this because I am hoping to get a cheap box to rebuild as a spare/replacement down the track and can refer back here.

 

Love your work mate.

Howdy Craig, why do you need to remove the nut?  Is it to fix reverse lever?   From my heaps of experience you could probably get away with removing the nut and washer and pulling lever off with-out mucking-up any thing inside.  Lever was a tight fit and I had to fit in vice, a screwdriver could probably lever the lever while on car.  Best ask someone with more experience.

 

 

Marty based on how spot on the rest of your car is I know for sure that this thread will cover all the important facts and tricks and maybe any special "Marty Made" tools that made the job easier

Aaaaah Special tools, I may have to make one, stay tuned.

 

 

The look and shape and area where that piece was found looks like it is from the reverse arm/lever. the one that actuates the reverse idler gear.

TerrA LX, you, my man, are on the money and have just become my knowledge bank. :-)

Edited by sibhs, 13 August 2014 - 11:07 AM.

[gad05]

Hi Marty ,

I to have a m20 to rebuild ( I think everyone has one in the shed lol )
Can't wait to follow the Marty method rebuild.
I think we will all learn heaps along the way.

Cheers Graham .

[sibhs]

Ok, I'm stuck.

 

I have removed c-clip but this end bit won't come off. It slides past where the clip was but stops as if it catching on a burr from clip groove????

 

 

Next is the front shaft bearing retainer. Do I make a 'Special Tool' to remover the retainer. Looks like it needs a very thin spanner, or are they available in shops?

 

 

Help needed on those things guys.

 

Thanks for support so far.

 

Cheers

 

Marty

Edited by sibhs, 13 August 2014 - 11:09 AM.

[N/A-PWR]

Great Thread Marty,

 

To find the burr on the spline,

 

clean the spline dry, and use a coloured texta which highlights the spline,

 

and then shift the gear onto the burred area several times, so the texta rubs off.

 

Where the texta has rubbed off the most/nonuniform area, would be your burr/interference to reduce.

 

Don't force the gear off.

 

 

 

I too need to do my M22 as well.

[TerrA LX]

Knocked out the lay shaft using an old one that was shorter. (That's what it says in the book, I used a piece of shifter handle and a big screw driver) Roller bearings fall everywhere. Leave cluster in box but disengage gears.

 

 

 

You have to cut an old lay shaft the same length as the cluster, this remains insitu when you remove the cluster after driving it's lay shaft out.

 

Installation is the reverse.
Vasoline/grease on the needle bearings will help hold them in place for re installation.

[76lxhatch]

I've used a length of reinforced rubber hose of roughly same diameter in the past, if you don't have an old shaft lying around

[dattoman]

If it all goes pear shaped I know a local guy who loves rebuilding these things and might have some info and parts

I also used to work for a wholesaler of trans parts and can still get some stuff if you get stuck

[sibhs]

I'm sure I'm missing something. I found this clip that puts pressure on keys, thought that might be it, but no. Tried the marker pen trick, no sign of rubbing. Do the keys lock it on in any way? Any other tips guys?

I'm sure I'm missing something. I found this clip that puts pressure on keys, thought that might be it, but no. Tried the marker pen trick, no sign of rubbing. Do the keys lock it on in any way? Any other tips guys?

[slar]

Thanks sibhs for doing this thread......this is the sort of stuff we need more of on this forum so it can be used for reference in the future.

I'll be doing exactly what your doing in the near future so this will be very helpful.

Really good...

cheers

Al

[sibhs]

Cleaned the casing bits then masked up the machined bits to protect from sand blasting.

 

 

 

 

 

 

Then a quick wash.

 

 

 

 

 

 

Then the Ali housing was walnut blasted.

 

 

 

Then a bathe in Ali cleaner, this stuff is ok, not really amazing or recommended.

 

 

Found the missing ring stuck inside cluster gear.

 

Edited by sibhs, 13 August 2014 - 10:24 PM.

[sibhs]

Hi Marty, yeh theres a spanner but have never seen 1 so have
used a pipe wrench (self energising/monkey wrench?) & thread
is LH so righty loosey on this 1.
Check the synchro dog teeth on the gears for rounding from
clashing with the synchronisor & for burrs in the synchro slots
that engage the ring & dogs.
Can help with a press if needed.

J

All my pipe wrench's are to thick, this needs to be 41mm wide and 3mm thick. Thanks for the press offer, what area do you live?

 

 

Great Thread Marty,

 

To find the burr on the spline,

 

clean the spline dry, and use a coloured texta which highlights the spline,

 

and then shift the gear onto the burred area several times, so the texta rubs off.

 

Where the texta has rubbed off the most/nonuniform area, would be your burr/interference to reduce.

 

Don't force the gear off.

 

 

 

I too need to do my M22 as well.

Still got me beat this one Dave. :-(

 

 

I've used a length of reinforced rubber hose of roughly same diameter in the past, if you don't have an old shaft lying around

I would expect the hose would be ok for refit but not to remove old shaft, seeing my shaft is stuffed I will cut it down to size. Cheers

 

If it all goes pear shaped I know a local guy who loves rebuilding these things and might have some info and parts

I also used to work for a wholesaler of trans parts and can still get some stuff if you get stuck

Thanks Neil, I will persist, but parts may be needed. I'm going to strip spare box soon to compare wear and tear.

 

Thanks sibhs for doing this thread......this is the sort of stuff we need more of on this forum so it can be used for reference in the future.

I'll be doing exactly what your doing in the near future so this will be very helpful.

Really good...

cheers

Al

Pleasure Al, just trying to spread the knowledge around, hopefully all my problems are solved on here for all to see.

 

Marty

[sibhs]

More Questions???   

I've been told the M21 gear ratio's will give me a better car to drive than M20..

Car is LJ 202 small Stromberg single carb, bigger valves, slight cam 3.08 diff, 13 inch sprinties.

Just want it for a cruiser.  

Your thoughts please.

 

To make it an M21 ratio is it just a matter of changing cluster gear?

 

Cheers

 

Marty

[rodomo]

That layshaft is fornicated. Look inside the cluster...................it's probably stuffed to.

[sibhs]

Yay, Rodomo,  you are the one that convinced me to give this a go. Thanks (so far)

 

Cluster looked ok, won't be an issue if I go M21.  Any more advice from someone with more experience than me???

 

How do I get that keyed thingy of the end?

[rodomo]

Thanks sibhs for doing this thread......this is the sort of stuff we need more of on this forum so it can be used for reference in the future.

What to look fors here:
http://www.gmh-toran...-or-bust/page-5

[S pack]

Yay, Rodomo,  you are the one that convinced me to give this a go. Thanks (so far)

 

Cluster looked ok, won't be an issue if I go M21.  Any more advice from someone with more experience than me???

 

How do I get that keyed thingy of the end?

If you want to go M21 ratio you will need to get a 497 V8 cluster, a 492 third gear, and an XU1 input shaft.

Alternatively XU1 ratio cluster and XU1 input shaft. Aforementioned parts are available as reproductions.

 

In either case you will also need to get an oil seal type front cover.