Gear teeth dressing

[Snagger]

Hi everyone.

I have just stripped down a Fairey overdrive bought as an overseas project a few years ago and have found an awful lot of internal damage.  There are a good many parts that need replacing, and if I was to renew everything that I was unhappy with, I’d be facing a parts bill of over £1000 (plus the VAT) by now.  So, I need to look at reusing what I can, especially since this unit is just a project and a spare.

To that end, the lay shaft gear cluster has damage to the teeth on one side of the rear gear.  All of those teeth have the same pattern, caused by enormous excess endfloat of the main shaft from bearing failure and the needle bearing supporting the input gear that meshes with the damaged end of the lay shaft.  The other sides of these teeth are good and the gear at the other end of the cluster is in great shape.

So, what is the best way to dress these teeth to try to make this unit not too loud to use?  Mechanically, the cluster will work, but it’s useless if it howls so much that it can’t be engaged.  The input gear on the back of the input shaft (that caused this tooth damage) is being replaced - its teeth are OK, but the interior bearing surface has been destroyed and the worn synchro dog teeth  make having it resurfaced for a bigger bearing (available from GLF) a false economy.

[Stellaghost]

32 minutes ago, Snagger said:

Hi everyone.

I have just stripped down a Fairey overdrive bought as an overseas project a few years ago and have found an awful lot of internal damage.  There are a good many parts that need replacing, and if I was to renew everything that I was unhappy with, I’d be facing a parts bill of over £1000 (plus the VAT) by now.  So, I need to look at reusing what I can, especially since this unit is just a project and a spare.

To that end, the lay shaft gear cluster has damage to the teeth on one side of the rear gear.  All of those teeth have the same pattern, caused by enormous excess endfloat of the main shaft from bearing failure and the needle bearing supporting the input gear that meshes with the damaged end of the lay shaft.  The other sides of these teeth are good and the gear at the other end of the cluster is in great shape.

So, what is the best way to dress these teeth to try to make this unit not too loud to use?  Mechanically, the cluster will work, but it’s useless if it howls so much that it can’t be engaged.  The input gear on the back of the input shaft (that caused this tooth damage) is being replaced - its teeth are OK, but the interior bearing surface has been destroyed and the worn synchro dog teeth  make having it resurfaced for a bigger bearing (available from GLF) a false economy.

Not familiar with the internals at all, however, the teeth could be dressed on a tool and cutter grinder, you could do it by hand at a push

Is the gear piece a single gear mounted on the shaft that could be put on turned 180 degrees so the backs of the teeth that are good will take the drive instead of the worn ones regards Stephen

[Snagger]

Reversing the gear would have been an very practical solution, as noise in reverse wouldn’t matter much, but the gear is integral to the cluster, just like the intermedia cluster in a Series transfer box.  At £250+vat, with the few vendors out of stock, it’s expensive to replace if it can be saved.

How would you dress the teeth by hand?  Just use a file?  I doubt any machine shop here in Dubai would touch them.

It looks like I might have to reuse that aft gear, too (RTC7187).  Craddock was the one supplier I saw listing them in stock, so I emailed them and asked them to do a physical check, and sure enough they don’t have any.   Typical, really.   One supplier of rebuild kits for these overdrives, GLF, sells the bearing and collar that disintegrated inside the gear (second photo shows the bits that welded themselves together, along with the photo below), but those are out of stock.  They also sell a larger bearing for exactly this case, where the gear can be turned to a slightly larger internal diameter.  That doesn’t help the dog teeth, but that’ll only cause a little backlash and this is just a project and spare, after all.

[simonr]

This thread talks about the gear - and gives a manufacturer.  The batch they talk about was never made, but someone suggests talking to the gear company - they might be able to make a one-off, or potentially fix yours?

https://www.lrukforums.com/threads/fairey-overdrive-input-gear-rtc-7187-now-in-production.211237/

https://www.goodrickgear.co.uk/

[Stellaghost]

2 hours ago, Snagger said:

 

How would you dress the teeth by hand?  Just use a file?  

Yes you could do it with a fine file but any motorized abrasive would do providing it sits comfortably within the confines of the teeth so as not to cause damage to backside of good teeth

I would begin with getting one damaged tooth into an acceptable condition and then make a gauge/template out of some 1mm plate that accurately follows the tooth profile. Use this across the width of the teeth as your filing etc so you maintain the same profile for all the teeth there after if that makes sense

Small amounts and patience are your friend, I would also look to add a molyslip or ptfe addative to reduce friction when finally in use regards Stephen

[Snagger]

9 hours ago, simonr said:

This thread talks about the gear - and gives a manufacturer.  The batch they talk about was never made, but someone suggests talking to the gear company - they might be able to make a one-off, or potentially fix yours?

https://www.lrukforums.com/threads/fairey-overdrive-input-gear-rtc-7187-now-in-production.211237/

https://www.goodrickgear.co.uk/

That was in 2016.  Craddock were the UK retailer, and they are out of stock.

GLF Classics have these rear gears sleeved if damaged, and will do mine for £50.  Given the state of the dog teeth, I’d prefer to replace it, but if there are none available, I may have to put up with that option.

[Maverik]

Worth speaking to Nige (Hybrid from Hell), I know he provides a gear polishing service at part of his diff rebuild service?

[Snagger]

@Hybrid_From_Hell, what do you think, Nige?

[Nonimouse]

Nick

I'm betting Rory will be able to sort once he's back from Saudi (he's due back this December). I believe he's going back to making choppers in Yobvil

If you can't get it to him, then give it to Streaky as I think his mutal friend is having Rory's toys sent back to the UK in one of his containers. Rory is back in Morroco, with Streaky middle of next year

[Gazzar]

I've got two of these to strip down. Might be a discount for three?

[ashtrans]

sorry to be pessimistic but I don't think those gears will dress, the pressure face has totally overheated and gone through the hardening,

we dress many gears with die grinders due to burrs from manufacture and small dents from bad handling when soft but the gear in the photo is too far gone I think, it will howl and will get worse as the surface hardening has gone,

[smallfry]

Die grinder or Dremel, but I have to agree with Dave Ashcroft regarding the hardening. I fear you will be wasting your time and will end up destroying the rest of the internals if put back into service. IMO these things would have been better if the gears had been straight cut, so no side loading. Might have been a bit noisier, but I wouldnt think anyone would have noticed 🤣

Probably better off off having one made ? Depends on cost I guess, but it wouldnt be at all difficult for someone with the right machine.

[Snagger]

1 hour ago, Gazzar said:

I've got two of these to strip down. Might be a discount for three?

If you are happy to strip one, then that’d be great.  Realistically, this one is looking like a donor.  The lay shaft cluster and input gear are screwed, the lay shaft has browned and has a small wear ridge, the main shaft seems OK but has been blued and browned by head at the back end and the clutch sleeve is predictably worn out.

[Snagger]

25 minutes ago, smallfry said:

Die grinder or Dremel, but I have to agree with Dave Ashcroft regarding the hardening. I fear you will be wasting your time and will end up destroying the rest of the internals if put back into service. IMO these things would have been better if the gears had been straight cut, so no side loading. Might have been a bit noisier, but I wouldnt think anyone would have noticed 🤣

Probably better off off having one made ? Depends on cost I guess, but it wouldnt be at all difficult for someone with the right machine.

The lay cluster normally sells at £250, and the input gear at £138, but no stock seems to exist.  Batches were supposed to be made in 2016, but I see conflicting information on whether that happened.  
 

This being just a diversionary project and a shelf spare for the Roverdrive, I don’t want to spend a fortune on it.  

[Snagger]

2 hours ago, Nonimouse said:

Nick

I'm betting Rory will be able to sort once he's back from Saudi (he's due back this December). I believe he's going back to making choppers in Yobvil

If you can't get it to him, then give it to Streaky as I think his mutal friend is having Rory's toys sent back to the UK in one of his containers. Rory is back in Morroco, with Streaky middle of next year

That’d be a good idea.  Streaky has just gone to Morocco for a break in the last couple of days - his cat got run over so he’s a bit fed up, and already needed a break after his recent scare.

[Nonimouse]

1 hour ago, Snagger said:

That’d be a good idea.  Streaky has just gone to Morocco for a break in the last couple of days - his cat got run over so he’s a bit fed up, and already needed a break after his recent scare.

I saw his post - he really loved that cat, and as you say he already needed a break. Rory has just gone back to Saudi after a short break here, so he'll be easy to talk into something interesting

[Snagger]

Buddy was a nice cat.  Cool, but friendly.  Met him a couple of months ago.

[oneandtwo]

I stripped down a Fairey a few years ago which had a worn layshaft (gear teeth faces starting to erode on Layshaft which they always seem to go first). Out of curiosity I rebuilt it with all new bearings throughout, and tested it against a NOS one which was in immaculate condition internally. Both made an equal amount of noise in use

In early 2000’s I found a good condition Fairey at our local tip still attached to a gearbox, they were more than happy to let me take it away.

[Snagger]

I had a new one in 1992/93.  It howled when engaged.  In fact, it sounded quite a lot like turbo whistle.

I have tracked down an engineering company locally that makes gears and does a lot of heat and case hardening treatments.  I might enquire about the costs of duplicating the gears or if they can just dress the teeth and case harden them again.  Can’t hurt to ask.

Meanwhile, if anyone has decent gears from a broken unit going spare… 🙏

[Snagger]

Well, the local engineering shop only makes gears for low speed machinery, not vehicles, as they don’t have the right grade steel.  To be honest, I didn’t think much of what I saw - most engineering shops here are very third world and don’t even have workbenches.  Their machinery looks basic, tired and neglected.  A good machinist can work wonders with old kit, but most here are badgers from across the water.  The fancy engineering company here can’t afford the time for single items - they’re busy making stuff for the oil and gas industry and have prices to match.

The good news is that with a bit more searching, I found a pair of gears, the last of a batch.  The only reference I found on the internet outside of comments in this thread that was any use was one on my blog’s overdrive rebuild guide, where someone else mentioned Goodrick Gears as per Simon’s suggestion.  It looks like I caught him just in time - he is closing down for retirement.

The gears are costing £500 inclusive, which is just a little more than the list prices on all the vendors who are out of stock.  So, fair enough.  It’s more than I wanted to spend, but as a project to do out here, one I can do with my son when he comes back for a few months, a useful spare and having seen the £1500+ prices for properly reconditioned units, it shouldn’t be a waste of cash.

 

[Anderzander]

Great news !  Well done 👍🏻 a good result from perseverance.

[Snagger]

Perseverance.  Stubbornness.  Sometimes hard to tell the two apart.  😉

[Snagger]

Well, I rebuilt it all, just could do with new clevis  pins and split pins (for the clevis pins and breather).  Came out well, and while considerably more expensive than originally planned, still a fair bit cheaper than buying a refurbished unit.