Series 3 A Less Leaky Transmission.

For the past few years I've been running a total loss lubrication system for the transmission, the gearbox leaked out of the front, back and top. The transfer case leaked out of the font and back and the over drive just leaked everywhere.

Something had to be done and few weeks ago 2nd gear was making all sorts of noises when trying to select it. Time to order in a new overdrive and some spare parts.

I already had a gearbox ready to go in so just needed to rebuild the transfer box.

Knowing that this would eventually need doing, especially when I drained the box and found a leaf spring and assorted dogs, I had made a few mods when rebuilding the gearbox. The main mod was aimed at blocking off the breather channel between the gearbox and transfer box. With no seals at the back end of the selector shafts I though that any oil that gets past them finds its way into the transfer box, the front end of the shafts seem to pass plenty and they have seals (of sorts). A small hole drilled just behind the rear of the selector forks would allow the oil to drain back into the main gearbox.

A new alloy sump plate was made for the transfer box and an alloy cover with a vent for the top so hopefully they should stem the flow.

So, have I been successful. Well, partly. After about a hundred miles I have a small dribble from the front selector shaft seals and annoyingly a persistent weep from the drain screw on the new overdrive.

One thing I do know is I'm knackered, I started on Saturday and I didn't finish until midday today.

How nice work. Are those machined '' in house"?

You will LOVE the Global Roamer Overdrive. It's a really well-built piece and contributes greatly to an improved driving experience.

What was the purpose of the small alloy disc and the two allen bolts?
The hole for the drain what is its position in relation to the gears beneath it , ie will it get a high volume of oil thrown at it by the 1st / 2nd synchro hub with the reverse teeth on the outer?
My current g/box leaks terribly from front of selector shafts ,it has the correct matched top, have replaced seals and also tried later seals with the ptfe wiper ring to no avail.

Rubins4 said:

How nice work. Are those machined '' in house"?

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Yes, all in house, it hobby crossover. Not time or cost effective but very satisfying.

offshoretitan said:

You will LOVE the Global Roamer Overdrive. It's a really well-built piece and contributes greatly to an improved driving experience.

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Its amazing how quickly things become the new normal. On my first drive I thought "wow this is quiet" now its just quieter. But yes, nice bit of kit, shame it leaks but I'm sure it an easy fix.

Blackburn said:

What was the purpose of the small alloy disc and the two allen bolts?
The hole for the drain what is its position in relation to the gears beneath it , ie will it get a high volume of oil thrown at it by the 1st / 2nd synchro hub with the reverse teeth on the outer?
My current g/box leaks terribly from front of selector shafts ,it has the correct matched top, have replaced seals and also tried later seals with the ptfe wiper ring to no avail.

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The disc fits inside the gear case to form a labyrinth. The plate on top of the transfer case has a similar arrangement.

I think the selector shafts are leaky by design, if anyone has a simple solution I would love to know.

When I had my box apart I fitted a strong magnet into the drain plug. The idea was to catch any loose chips and hold them to prevent futher damage.

I like that the position inside the box is good and the plate should stop bulk of oil splash well thought out modifications.

rob1miles said:

When I had my box apart I fitted a strong magnet into the drain plug. The idea was to catch any loose chips and hold them to prevent futher damage.

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Should have thought about that at the time, I was going to change all the oils after about a month, might be an opportunity to fit some. Do you remember where you got the magnets from and how did you attach them?

Blackburn said:

I like that the position inside the box is good and the plate should stop bulk of oil splash well thought out modifications.

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Dont know if this mod is going to make a significant difference but I guess it can hurt.

Re magnets, I looked on e-bay and found some round flat ones that were the right dia to fit in the plug. One a £1 or 2. I then set one in with aradite. I got the idea from helicopter gearboxes, they have a several rings of magnets to catch chips to keep the box running for the few minutes it takes to get down safely. The idea I really like but was beyond my skill is the drain plug used in gas-turbines. Its two concentric magnets with a thin (5 thou) brass sleeve between, each magnet has a termial on the outside. Weekely you put a ohm meter across the terminals. If there is metal in the oil it bridges the gap and the restance drops. There used to be a limit figure for pulling the gear box.
Just done a check, you can buy them. Could be worth a visit to an aircraft breakers?
http://www.allenaircraft.com/products/chip_detectors.html

Cracking ideas and nice bit of machining too! I'm about to embark on the great gearbox seal up! Any chance you would be happy to machine up the same mods and perhaps sell them on?

Cheers,
Ben

Ben,

As I've mentioned, neither time nor cost effective, you could buy in the alloy sump for a lot less than I could make it, I think it was over £50 just for the 25mm thick alloy tooling block.

I only have small end of life manual machines from the 70's so things like this take an absolute age to make.

The only real mod I've made is in the way the transfer case breaths and I'm sure these mods could be equally well made with a hand drill and some patience.

Citizen Kane

Cheers for the reply. I get where you coming from. Have you had a chance to drive with the breather mods? Have they made a significant difference? I have access to some old manual machines too, so may have to borrow your ideas.

Ben

Its strange but whenever I see a thread with gearbox on it I hide behind the settee. I can point to mine and know where to squirt oil but apart from that they give me the collywobbles. However I just got brave enough to have a look and yours in the same place as mine so I presume all is well.

It looks a tad cleaner than mine though

btiratsoo said:

Citizen Kane

Cheers for the reply. I get where you coming from. Have you had a chance to drive with the breather mods? Have they made a significant difference? I have access to some old manual machines too, so may have to borrow your ideas.

Ben

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I guess I have about 600 to 700 miles on this transmission now and all I can really say is that it dosnt seem to have any adverse affects. No leaks from the transfer box so I assume its breathing ok but I assume any freshened up transmission would be the same. No sign of the level rising in the transfer box but equally I cant detect any drop in the gearbox level and I know its leaking past the selector shaft seals a bit.