Series III gearbox rebuild

[Snagger]

There you go Snagger...........guys are looking after you.

He can't be working for Boeing - I can't hear myself think in the 73, and I've heard the figure 98dB banded about several times (only heard it on the ground, though...) Most of the acoustic work on aircraft would be the engine nacelle designs. They have porous inner metal linings to trap sound and it's extremely effective. A gauze or mesh material on the underside of the tunnel cover, seat base and foot well panels should be very good at reducing transmission noise.

[Gazzar]

I think he specialises in much smaller aeroplanes, but much faster. Much MUCH faster. Anyway, his advice, when asked was "bitumen". One word. Seems to work, cheap and available.

G.

[Bhart]

I have a question regarding the primary input shaft oil seal;

I have a leak in my NOS, Army surplus gearbox. EP90 is dripping (almost pouring) out of the bell housing weep hole after a short drive. It's got to be the seal of or the gasket in this area.

My concern is re-attaching the oil seal housing. I realize there are 3 (?) bolts holding this cover on, along with some studs and nuts. Will I be able to tighten the bolts without further removing the bell housing from the transmission? Don't want to have to go in too deep for a fairly simple repair.

[Snagger]

The bearings are held in by separate retainers with their own bolts - you can remove the front cover, replace the gasket and refit everything without disturbing the bell housing attachment fixings.

[Bhart]

Thanks.

[Gazzar]

Updates:

It's miserable outside, so I'm doing indoor work: I've cleaned up the bellhousing and the selector mechanism top - and found the serial number, it IS a suffix "D" box. The earlier breather arrangement has been fitted, so I'll have to ensure that this works as it should.

I'm going to replace all the bearings and springs in the selector housing - it would be a shame to have a great box with a poor selector.

Pictures later.

I'm going to start on the transfer box next.

G.

[Gazzar]

Just finished taking the transfer box apart.

Some pictures!!!:

Filthy mucky bellhousing!

Cleaner bellhousing:

Selector housing.

I cleaned this up and found the serial number on it, as indicated by the tell-tale areas of the 3rd 4th syncro this is a "D" suffix box.

Dissassembly is very straightforward, even with the modifications this particular box.

Note the earlier vented cap/filler arrangement.

A 7/16ths spanner does the job on the reverse/3/4 selecter detent spring holders:

And the larger 13/16ths spanner removes the brass 1/2 selector detent spring holder:

Revealing a rubber seal. I'm not sure that this is right - I thought there'd be an "O" ring, I'll check the parts manual later.

All the bits:

Repeat for the other side:

And the selector shaft seal retainers:

More anon!

G.

[Gazzar]

Right! On to the transfer box!

Transfer box in all its glory!

First of - remove the speedodrive housing,

The nut on the output shaft was loose - remove the "splitpin" and undo.

Revealing the raw output shaft.

Next, undo the housing using a socket

Six nuts and spring washers later:

and

The speedodrive is revealed.

It isn't nearly as rusty as the photos suggest.

The speedo pickup is the same - all is fine here:

Next up - the front output casing.

Remove the access cover

And then the shaft detent spring and plunger.

And finally the pinch bolt for the selector shaft:

Undo the housing retaining bolts:

And the output casing just eases off the transferbox proper!

Revealing the 4x4 dog, and the correct order for the selector shafts.

Next up; disassembly of the output housing!

[Gazzar]

Remove the output flange, by unpeeling the split pin and undoing the castled nut, 9/16 ww socket.

Remove the selector dust cover (this is much better arrangement than the system used on the series 1) by undoing the the 3 bolts and uncliping the 4x4 pull.

Hummmm, the cover wasn't doing much good, was it?

Selector shafts coming free:

And all the way out!

And 4x4 output shaft

There IS a bearing in there somewhere!

This is the selector mechanism, DO NOT MESS WITH THIS, unless you have to, as it's unnecessary, and can be a pig to reset.

For cleaning it slides of in one piece.

Cleaned and temporarily reassembled (I don't think that this is right - the sleeve should be on the otherside of the stepped sleeve).

The selector set up on the peg.

Removal of the front output seal housing:

And the last instalment for today?

Removing the main output shaft of the transfer box (not easy).

Soon, after the break.

[Gazzar]

Sorry about the break - dinner time.

The main output shaft of the transfer box is held in place with two bearing races, and they are FUN to remove.

First, start by tapping the whole shaft backwards - this drives out the rear outer race.

You can see the front bearing assembly coming apart here:

All the way in,

and the rear outer race, all the way out!

Front inner race from the inside of the transfer box.

More in a minute, photobucket is giving trouble.

[Gazzar]

Next up, the front bearing outer brace.

This is held in with a circlip:

Remove the circlip:

and then the manual suggests making a "packing piece" to act as a distance piece to that the outer race can be tapped out from the back, using the inner bearing as a drift.

Take one layshaft bearing:

And cut it up!

Pop it between the inner race and the outer race:

Wedge it between the two parts:

Use a deep impact socket over the thread to protect it:

And whack away.

Bearing out!

To be honest I found this quite tricky, it was hard enough to balance the distance piece against the outer race and hit the socket at the same time. I found that a small amount of heat eased the whole process.

The inner race has to be removed next.

Using a cold chisel this was drifted of the shaft, simple enough, actually.

And then time to remove the gears.

And I found a problem!

The cuirclip holding the gears on is removed in the normal fashion, however the ears on mine had disap ear ed!

Time for the cold chisel again.

Not pretty, is out.

Thrust washer, helical gear and spur gear, all removed, and shaft removed from box.

Finally, the rear inner race had to be removed.

Again, using the deep socket to protect the threads, it's big hammer time!

Several taps of the hammer only shifted the inner race a little bit, however hen I applied heat the whole process went much quicker. Nicer too, as it was flipping freezing in the garage!

I'm done for now - and am not sure when I'll get back to this, but it will be soon!

G.

PS what's common practice with circlips? Replace all of them?

G.

[Briarston]

I don't have a series 111, and never tried to pull a g/box apart (except a motor bike one, years ago, and didn't have much success rebuiling it!) but I am following this rebuild out of interest in things mechanical.

Looking forward to the next instalment. I'm finding it very informative and good photos also.

Well done!

[rusty_wingnut]

I found when I did mine a few years ago, that the blow lamp is your best friend for getting one of these apart, makes the whole process so much easier.

[lexi]

Very good Gaz.. The box looks "slightly neglected" . Problem with rust is it tends to eat into case hardening doesn't it?

You not got your parts washer going?

[Gazzar]

Parts washer is fine - I was more focused on stripping down the box, before I clean it. The gears and shafts are spotless: the rust came from the bearing cages.

I've not found a "fault" with the box yet - I suspect the vehicle died before the box did.

I'll do a shopping list up and then get the parts. I think I'll bring the seals to a seal supplier and get the double lip versions, the same people should do the speedisleeves to recondition the output shafts.

Glad that people are enjoying this, I certainly am!

[Snagger]

Circlips should always be replaced with new, even if the ones fitted appear faultless. I even replaced the clip around the main gear box main shaft after the trial and error of setting the 3rd gear end float, even though I had used a new clip on initial reassembly - they are quite brittle and the stresses of opening them for removal can create fractures. The last thing you want is to have to strip the units down again for the sake of re-using a clip that costs pennies.

I think the bigger clips for the bearing carrier are fine if they appear to be undamaged - they open a much smaller proportion of their diameter than the smaller clips, so are put under less stress on removal, but if you can source new clips, so much the better.

[Gazzar]

That's what I thought, thanks Nick! Last time I did this I used the old split ring for the trial setup on the bronze bush, and only used a new one once everything was within spec.

In summary; Replace small, keep big, unless damaged in which case - replace!

G.

[lexi]

Very enjoyable and nice of you to post it all up mate.

[Andy]

Sure looks much easier to spilt the t'box out of the truck. I've just got mine back together a week ago doing in place as the selector shafts had seized. It's an utter sod to get it all back as there isn't room to remove the housing & I was working blind with my hand inside it to line it all up. I did swear lots & needed help to get it sorted. Works now though

[Gazzar]

I found when I did mine a few years ago, that the blow lamp is your best friend for getting one of these apart, makes the whole process so much easier.

Totally agree, I'd go so far as to say to do a decent job you would need access to a source of heat!

[Gazzar]

Sure looks much easier to spilt the t'box out of the truck. I've just got mine back together a week ago doing in place as the selector shafts had seized. It's an utter sod to get it all back as there isn't room to remove the housing & I was working blind with my hand inside it to line it all up. I did swear lots & needed help to get it sorted. Works now though

You got that sorted then? Good, you might need it in the next month or so!

G.

[Gazzar]

Updates - minor increments, rather than service packs! I've cleaned up the transfer box and the parts, all looking fine so far, but I'll go over them thoroughly later on.

I'm putting together a parts list for the transfer box - pouring through the parts book (bliss!).

G.

[Gazzar]

So, shopping list for the mainbox innards:

We've established that it's a Suffix "D" box or later.

Reverse gear assembly FRC1810 (complete)

Reverse gear location pin 591519

Input pinion bearing 55714

Selection of adjustment shims 594021, 594020, 594019, 594018

Circlip 214795

Seal 571059

3/4 syncro clip (three of) RTC1956

Mainshaft roller bearing 6397

Spring clip RTC1957

Shim selection RTC1962, 50702, 50703

3rd gear FRC8179

Bronze bush (singlepiece) 571218

Selection of thrustwashers 267572, 267573, 267574, 267575

mainshaft pin 6405

mainshaft pin RTC1979

1/2 syncro detent spring (3) 503805

1/2 syncro detent ball (3) BLS108L

Circlip (inner) 9960

Mainshaft rear bearing 1645

Circlip (outer) RTC1984

Mainshaft output seal 236305

Layshaft locktab 528683

Layshaft distance piece (selection) 528720, 528721, 528722

Forward layshaft bearing 528701

Layshaft "C" onward FRC2084

Layshaft aft bearing RTC1412

Gaskets set 600603.

Have I missed out anything? Or am I being over cautious? I'm fairly certain that the above list will result in a quiet reliable box.

That's all from me for the next while. I'll be looking at the transfer box next, but it might not be until the week after next.

G.

Next up - the mainshaft gear selectors and associated gubbins:

I've not checked out the spare lever I found when back at my old place so I may have to add to this list when I strip it down.

Plate at top with breather: FRC4007, 22G1941

Mainbox gear lever FRC2046 (generic is fine) + "O" ring FRC1387

Spring for lever 219723

Knob 576316 Ferrule spring thing 571661

Springs fr reverse gate (two of these) 231116

Tab washers for gear lever: (four of these) 2499

Selectors

Seals for side detents (two of) 5852

Springs - 1/2 & 3/4 (two of) 3649

Spring (reverse) 56102

detent balls (three of) 1643

interlock detents (two of) 55638

Front selector seals (two) 272596

Front elector seal 272597

Transfer box

:

Front output shaft bearing: 217490

Circlip CCN112

Thrust washer: 90217488

Intermediate shaft bearings: (two) 599869

"O" ring - strange place in parts book! 532323

Thrust washers(2) - 561197

Thrust washers (2) 521328

Output shaft back bearing 90217512

Rear seal: Front (two) FRC1780

Felts: 622042

Mainshaft bearing carrier (bearing)217478

Speedo cable rubber 6860

Front output casing

Bearing 217325

Seal for selector 512791

Castle nut 3259

Split pins PS608101l

I need to look closely at the gear selectors for the transfer box - so I'll add ot this list later, but I think that the bulk of it!

[discomikey]

dont suppose you know if a coiler speedo gear set will fit in place of the leafer ones? if so my speedos an easy fix.

[ejparrott]

I don't think it will