091 clips for 3rd and 4th hub on 002 main shaft

[Bruce2]

I don't think a how-to has been done for this modification. If it's been discussed, post the link (I couldn't find it).

Dave posted this in another topic:

The 091 circlip is 1mm thicker, (approx. 2.5mm total thickness) so I always begin with a cut of 0.87 to 0.9mm on the 3rd gear side to get it close. Once the end float is set for 3rd, then do similar on the 4th gear side, bit by bit, so the clip is tight, width wise.

You must still check that you have enough end clearance on 4th with the hub pressed lightly against the 4th-side-circlip. By all means, centre the hub after this check, but on operation, it will always end up closing the gap on 4th, so make sure you have the end play in that thrusted position too.(no less than .004", for me never less than .006"!!)

3rd gear can have a little MORE play, since its helix will help pull it into gear, but 4th gear pulls away from the hub, so too much end play means the dog teeth have to work harder to keep engaged when the end play is large.

I bet Dave's lathe is a few steps from his work bench so it's easy for him to cut-n-check. My lathe is about 10km away, so does anyone use a predetermined amount of machining on the hub?

[Casting Timmy]

Good timing, I just recently went through this and talked about it with some guys on Facebook.

I premachine the third gear side a little so it sets up and goes better in the lathe. Then I use feeler gauges once third is set to measure between the hub and the end of the clip grove on the fourth gear side. Then measure the clip thickness to know how much to remove/ pocket on the fourth gear side.

David - Every job I do gets the 091 circlip mod, otherwise the hub moves toward 4th gear and 4th is too tight and 3rd has too much end float.
usually, once the mod is done, 4th has too much end float, so the shoulder has to be cut back, and a 2.6 to 2.8 corclip is used on the end to retain the bearing.

Tim - I do cut the third size a hair short for the first mockup as fourth does seem to grow on me a little.


Instead of a lathe why not use a counterbore tool with a custom pilot for a slip fit in the splines of the hub so it automatically centers? Or make a tool like a lifter radius tool for a VW engine case, except sized for the correct diameter of the clips?

I'll also work on posting a picture that shows how I do the calculations, that will be a lot better than me trying to explain without it.

[Casting Timmy]

When I go to cut this one I will probably shot for removing .009" or .010" instead of the full half of .0135". Fourth does tend to grow, so I cut it a few thousandths short and then check it, usually this makes it better than going for the full split. (Usually checking shows a even split)



After this I measure between flat hub surface on the fourth gear side and measure the clip thickness, the difference is the amount to pocket fourth gear side to lock it in place. I do see variance with the 091 clips when it comes to thickness, maybe another solution would be grinding the clips to the right thickness.

[Pablo2]

The cut on 4th gear side needs to be angled, to allow easier removal of the circlip at rebuild time. The first time I did this mod, even though I angled the cut somewhat, I failed to allow enough leeway for easy removal and man, was it a bitch.

[dangerous]

Bruce, I think if you just want to 'improve the situation' from stock,
then some round numbers can be used to make the situation 'better'.

But I doubt you could consistently end up with 'tight' retention of the hub,
unless you do the machining in a few steps, with trial assembly between.

Yes, the diameter of the recess on the 4th gear side needs to be larger
than on the 3rd gear side to enable clip-removal.
38mm on the 3rd gear side and 39mm on the 4th side, but I will confirm these numbers for you later.

edit: 37.1mm diameter on the 3rd gear side and 38.9mm diameter on the 4th gear side.

Knowing what you are trying to achieve,
I would leave the 3rd circlip alone, and just recess the 4th side to use the 091 clip,
and then on assembly, just make sure the hub is pressed lightly back toward the 4th gear side.
(because that IS where it will end up!)

Just as a guess, the 4th side recess would need to be around 0.75 to 0.8 deep, but you may have to develop a method/depth.

If you want to do both sides of the hub,
you could go 0.95 deep on the 3rd side to give yourself an extra 0.05 than what the 002 clip gives,
and then perhaps 0.8 to 0.9 on the 4th gear side.
My guess is, the hub will still have some clearance to the circlips
but at least you are reducing the chance of the 4th gear clearance closing up as much as with the 002 clips.

I will take some notes next time I do one and perhaps edit what I have written.

[Pablo2]

The reason we got in the habit of machining both sides is that we often installed loose needles on 3rd gear side (more to fit low ratios than for "added strength"). The gapless circlips that allowed loose needles on circlip mainshafts only came in 1.25 thickness. Since the 002 circlip is 1.5 thick, the best way to accomplish what we wanted was to machine for 091 thickness and use 2 gapless clips.

[Bruce2]

Going to do the mod on 4th gear side only. Will let you know the result.

... and a 2.6 to 2.8 corclip is used on the end to retain the bearing.

Where do you get the thicker clips?

[dangerous]

they are 3rd gear circlips used on the end of the mainshaft. Weddle and Erco have all the sizes.

[Casting Timmy]

When needing to run the thicker circlip on the end of the mainshaft, is that because you're using stock washers under the synchro cone when putting the 113 gears on the 002 shaft?

I recently did an 002 shaft with the 113 gears and used the conversion washers from Weddle, I ended up having to sand down the gears a little to get clearances where I wanted them. The extra thickness definitely adds and made it where I wasn't worried about adjusting lengths.

I've also been wondering why and how much it takes to move the hub. Does the hub move because of third gear thrusting into it? If the stock 002 clips allowed it to move, but lasted for a while in stock applications. What kind of power levels does this start making a difference?

[dangerous]

Yes the hub moves due to 3rd gear pushing against it. I see this even at stock power levels.
(which is why I do the 091 circlip conversion on ALL 002 shafts' stock rebuilds)

The thicker end-circlip is used AFTER you machine the bearing shoulder.
The bearing shoulder has to be machined
because in most cases the 4th gear has way too much end float,(after 3rd float is reduced).

The above is with reference to 002 style gears only.

I have used Weddle's special 113 washers,
and find they make the synchro sit a little high,
even when the gear has the correct end float on its own.
Last time I HAD, to use a worn out synchro because I had already welded the cone on!

For the conversion using the 113 gears on a 002 main shaft,
I only machine the hub enough in depth and diameter
to get the correct end float with unmodified-length 113 gears.
(just the counter bore diameter in the gears)

[Bobby74]

Forgive me if I'm way off base. I haven't built any custom gear stacks yet, but planning my next setup.

Would it be possible to use aftermarket shims and circlips to set the endplay or even align the gears on the shaft (maybe with minimal machining?) for proper spacing/loading? Maybe a combination of circlip and/or shim?

Shims:
https://www.mcmaster.com/#shims/=1ai1o3u

Circlips:
https://www.mcmaster.com/#circlips/=1ai1p2e

Just trying to think outside the box for a cheaper/easier solution.

[Bobby74]

Not to beat a dead horse, but this is kinda bugging me.

I found an old post about a T4 411/412 Manual trans I used to own that has the whole gear stack accessible from the "drain pan", as I call it.

Ray Greenwood wrote:
"Remove the 3" snap ring and the 11 outer case bolts and the whole mid section case pulls off ...revealing ....a 3 foot long pinion shaft standing up out of the differential assembly. On it...is all of the gears. The key is...that the gears have set shim thicknesses between them...so that the gears are positioned only one of a couple of ways. Hence they reason why you only need one of two sizes of shim for the counter shaft location. The key is that the thrust washers are set to the case machining. As long as you never swap the mid section of the case, the gears will always be in correct relationship to each other with the shims they came with. I have had to swap mid-sections before. You do it if any gears are ruined. The donor tranny gives you all the gears, the mid case and shims...and the pinion carrier shim. The main stack gear shims rarely wear, and if they do...just replace them with what came out and you are back to normal. "

So.... Could we take VW's late model 411/412 design idea and adapt it to a 002 or 091 trans? Set the gear stack with shims/circlip adjustments so it works best and forget all the machining?
Yes, I'm cheap and stubborn

[Pablo2]

I'm not sure where the shims and circlips that McMaster offers would help us on the mainshafts (other than perhaps the spirolox) .. but that's a great resource to keep in mind. Thank you for the links.

[Bruce2]

edit: 37.1mm diameter on the 3rd gear side and 38.9mm diameter on the 4th gear side.

you could go 0.95 deep on the 3rd side to give yourself an extra 0.05 than what the 002 clip gives,
and then perhaps 0.8 to 0.9 on the 4th gear side.

I thought I might update what I found when I did this mod a while ago.

I had 4th gear side of the hub machined to a diameter of 39.0mm. When I assembled it, the clip just snapped in place. I did not attempt to remove the clip, so I don't know if someone in the future will experience what Paul did when he didn't cut it large enough.

For the depth, I went 0.9mm deep. I know 0.8 would have been on the conservative side, but I didn't want to be making another trip to the lathe. I also thought that what I was doing would be better than using the thin 002 clips. At 0.9mm, when I assembled it, I pressed the hub against the clip on 4th gear side, since like Dave said, it will end up there anyway. This resulted in 0.45mm of endplay on 4th and 0.3mm on 3rd using stock 002 Bus gears. I had two hubs cut the same, so I can see what the endplay will be on the next one. If the same, I think I will go 0.95-0.98mm.

[Bruce2]

Update 2.0:
I just used the second hub I had, and the endplays were:
0.50mm 4th
0.38mm 3rd

in both cases 3rd had less endplay, so the next time I think I'll machine them deeper, 0.95-0.98mm.