23 replies to this topic

[alex-95]

My Idler gear has been rattling recently, so I’ve taken the engine out to investigate. I’ve found the gearbox casing and transfer housing has worn on the faces the shims sit against. ( it’s not the first time I’ve had this problem, 1st time the gearbox was like it as I had bought it see this thread. https://www.theminif...ear-and-casing/). It’s a different G/box casing and transfer casing to the previous issue. It’s worn on the bottom of the face on both cases. I set the clearance correctly, it hasn’t done loads of miles maybe 6k. What can cause this problem other than the casings being misaligned? I noticed a bit of ‘slop’ between the mesh of the idler gear and 1st motion gear, but with the idler only in one bearing it’s hard to tell exactly how much. ‘slop/backlash’ there is between them.

I’m going to machine the casings flat again but don’t want it to happen again.

[ACDodd]

You won’t stop it. Reduce the torque going through them.

Secondly grab the input gear on the side of the gearbox rapidly and sharply turn it to and fro. If you hear a clatter it’s because you have too much backlash in the main gearset.

Ac

[Aridgerunner]

With any luck I'll be assembling my engine sometime next week and then attaching the gear box. My question is, would it be a good idea to put some type adhesive on the case side of the thrust washers? That would serve to stop them from spinning in the case faces.

[Spider]

Hey Alex, sorry to hear you are still having this issue.

Given the wear is occurring in one area of the thrust faces, that can only happen from the gear tilting and / or the faces aren't perpendicular to the shaft of the idler or there's excessive clearance of the shaft in it's bearings. I don't think the issue you are seeing is from misalignment.

Can you post up some photos of the case, the housing and the shaft of the idler ?

[alex-95]

You won’t stop it. Reduce the torque going through them.

Secondly grab the input gear on the side of the gearbox rapidly and sharply turn it to and fro. If you hear a clatter it’s because you have too much backlash in the main gearset.

Ac

 

Cheers Ac, I've tried turning the input gear sharply and there is a bit of clatter, I don't think its any worse than other Gearboxes I've tried it on but it maybe the cause of the noise.

 

With any luck I'll be assembling my engine sometime next week and then attaching the gear box. My question is, would it be a good idea to put some type adhesive on the case side of the thrust washers? That would serve to stop them from spinning in the case faces.

 

I've thought about fixing the shims but not easy, I don't think there would be anything suitable to stick it.

 

Hey Alex, sorry to hear you are still having this issue.

Given the wear is occurring in one area of the thrust faces, that can only happen from the gear tilting and / or the faces aren't perpendicular to the shaft of the idler or there's excessive clearance of the shaft in it's bearings. I don't think the issue you are seeing is from misalignment.

Can you post up some photos of the case, the housing and the shaft of the idler ?

 

I was wondering if it was the bearings, I think I've seen a post saying the Koyo ones aren't as good as the Torrington ones? Yeah I think I checked the alignment as I did in the other thread so that should be ok.

 

Heres some photos, I don't think its as bad as the 1st one and it looks bigger as the casing has a bur on the worn edge to the original good face.

 

 

 

[Spider]

Thanks for the photos Alex.

If there is a 'tapering' there, then I'm wondering if when setting the clearance / end float, you were measuring at the top, where the clearance is greatest and so set it too tight?

It doesn't look to be normal wear but suffered a break down of lubrication, picked up and chewed. I have seen much worse. Could you post some photos of the Thrusts ?

 

The Koyo Bearings are very good quality but I * think * they have 1 less roller than the Torringtons, I may well be wrong on that though, but it might be worth checking.

 

[alex-95]

Thanks for the photos Alex.

If there is a 'tapering' there, then I'm wondering if when setting the clearance / end float, you were measuring at the top, where the clearance is greatest and so set it too tight?

It doesn't look to be normal wear but suffered a break down of lubrication, picked up and chewed. I have seen much worse. Could you post some photos of the Thrusts ?
 
The Koyo Bearings are very good quality but I * think * they have 1 less roller than the Torringtons, I may well be wrong on that though, but it might be worth checking.

I think the tapering may have been the issue. I machined the faces and fitted it together, the idler gear was locked solid, got the smallest shims I had and still locked solid. I machined a Brass one just to get clearance which I got. The idler span freely (over 1 whole rotation) but would then randomly lock solid again. When it moved freely I could get thicker feeler gauges in one than the other. I’ve tried another transfer housing and that does the same. I’m 99% sure the gearbox face was within 0.01mm before I machined it so can’t see that’s causing an issue. I fitted new idler bearings and I’m pretty sure they went in parallel ( and can’t see that’s causing they would go in all the way if they didn’t go in.

The Thrusts had a tiny bit of casing pickup on them and one looked like it’s got hog with heat marks on it (unless that was from factory?) but I lapped them before I could see your reply.

Ok Ideal, can’t remember where I read that but will keep the Koyos then👍🏻.

Can the thrusts be ground down? I guess they’re case hardened so don’t want to grind through that. But I have loads that need a bit of a clean up and may be handy to gain 1 thou clearance compared to a standard size thrust.

[Spider]

OK gotya in that so far.

 

The faces in the cases look like they need dressing, so I'd suggest doing that first - if in fact they need that (I know looks can be deceiving !).

This maybe why with your dummy thrust you are getting a lock up and / or there's some crud in the bearing - from what's been left after the faces have picked-up on each other.

There is a bit of thickness to the hardening in the standard thrusts, I've never ground through them to see how deep the case is, but you should be OK taking 3 - 4 thou off. The faces, as supplied, are bright. It appears to me that in manufacture, blanks are made with the ID, OD and oilpath cut in them before hardening, then following heat treatment, they are then ground to final thickness. This is how I have made them too.

Can I also suggest checking the gasket face is parallel with the thrust face and perpendicular to the Bearing tunnel. You should be able to do these checks in the mill.

 

[alex-95]

Sorry, I don’t think I made it very clear and think I made it confusing saying about machining a gearbox previously? So the above photos are as I found the casings after stripping it last week and have since machined the faces so they are all good. I did think about checking the bore to the face when it was on the mill but annoyingly I didn’t have time to remove the bearings so couldn’t check. I wonder if I turned a shaft with a shoulder to be a good fit in the bearing diameter in the casings and made it so I could attach a DTI to it then I could turn it while touching the gasket faces in a few areas which would then give a rough idea how perpendicular the bore is to the face? Something must be off to cause the issue but not sure what, dowels seem good considering 2 transfer cases fit and I checked if the dowels weren’t bent.

Ok ideal, I’ll grind one up and check the hardness before and after.

[Spider]

Ah, my bad - sorry there.

It does look like there is / was a taper fit somewhere. There's always more than one way to skin a cat as they say, likewise, there are other ways to check the fit of the housing to the gearbox case for tapering here.

Perhaps see if you can get 2 x long feeler strips down each side of the idler axle, such that they go all the way through and take up all clearance, then see if you can get a thin one in top anywhere. Not ideal, but may show an issue.

I really feel to properly check the bearing housing alignment, the bearing needs to be pulled.

It's possible that the housing maybe distorted from someone using heat in the past to pull the bearing. I've found quite a few like that.

[alex-95]

No worries!
I think I’ve found the issue, I removed the bearing from the gearbox and made a clocking tool which seems like it’s giving credible results, brass bit is a good fit in the bore, rotating about that axis I can get zero on the left side and then it’s roughly 0.15mm (6thou) lower on the opposite top corner. See the photo below. But that ties in with me having a gap one side and not the other but doesn’t explain why it locks up after it’s turning freely for a full turn, unless it’s the helical gears twisting the gear into the face?
I think I’ll have to either clock the bore true and machine the face to that bore or get another casing, which will probably be easier.


https://i.imgur.com/...&fidelity=grand

[ACDodd]

Ok now I have seen your damage it is much worse that I believed. You are on the right track, maybe the best option here is to mount the transfer case to the gearbox after centring on the original bore, and then boring all the way through the transfer case and into the gearbox to achieve perfect alignment, then sleeve back both housings to retire original sizes. This way bearing bores will be in perfect alignment and the thrust faces can then be machined square to the new bores.

Ac

[alex-95]

Ok now I have seen your damage it is much worse that I believed. You are on the right track, maybe the best option here is to mount the transfer case to the gearbox after centring on the original bore, and then boring all the way through the transfer case and into the gearbox to achieve perfect alignment, then sleeve back both housings to retire original sizes. This way bearing bores will be in perfect alignment and the thrust faces can then be machined square to the new bores.

Ac

Cheers Ac, I think I'll have to do that at some point. Luckily I have a few spare casings in stock so Im in the middle of swapping the gears into the spare casing.

[alex-95]

So the saga continues, and to cut a long story short, I built the gears etc from the above gearbox into another good casing and got a good transfer casing. Got it all back in the car and Annoyingly it still has a rattle, which can be heard in the below video(if it works) the noise stops when the clutch is depressed. So thinking it could be backlash in the main gearset as Ac says.

What’s your thoughts on it? I don’t want to remove the engine again if I could get away with running it with the rattle but don’t want to damage the engine or gearbox.

https://imgur.com/a/V9YOa8w

[alex-95]

Also increasing the revs slightly (pretty much I think) stops the rattle. Like idling at 800-850 and increasing it to 950 -1000rpm