4th gear axial end play

[Bruce2]

Even though the bentley doesn't specify to check the axial endplay of 3rd or 4th, I noticed on the current gearbox I am building that 4th had excessive endplay.
It is a late SSC IRS gearbox with 002 type gears. 4th gear endplay measured at .53mm, whereas the spec for 1st and 2nd is .1-.25mm. I think over half a mm is excessive.
What do you all think?
What's the remedy?
Machining the mainshaft? If so, where do I get a thicker circlip to take up the extra on the outside of the bearing?

[Marc]

3rd gear endplay is set by using a selective-thickness circlip (also to .1-.25mm, low end of that range is preferred).
OEM VW were 1.45 through 2.20mm in .15mm increments (113 311 381 through 386) plus 2.30mm (113 311 387); Long Enterprises sells the three thickest ones individually as well as a kit (LE92) that contains 1 ea 1.60, 1.75, 1.90, 2.05, 2.20, & 2.30 mm (382 through 387).
4th gear axial movement is controlled by the spacer spring, there's no factory accommodation for setting it on the late-style gear stacks.

[Pablo2]

Bruce is talking about idler gear end play. Yes, .53 is pretty excessive, but the late hubs/gears do require more oiling clearance than the early 113 type. (.. and I also think that tight end clearances have been "encouraged" too much.)

First, make certain the 3/4 hub isn't pressed too deeply/hard against the inner circlip. When installing 3rd/4th slider/hub assembly, I almost always have to press lightly back (outward) to re-center the hub. This is especially true of 002, which has thin circlips that bend. (I now only use 091 circlips, which require a bit of hub machining).

I honestly think it's best to divide whatever your total clearance for 3rd & 4th you have, and distribute it between the two (by machining the hub for 091 circlips). I like this more than machining and moving the mainshaft forward.

[Marc]

Ahhh, I get it now. Those are good tips - at the minimum, one shouldn't be overzealous when pressing on the 3/4 hub because as you say the stock circlips can deform.

I should've specified that the super-tight end clearances are best kept to "drag-race" applications, where the added stability justifies the possibility of limiting lubrication... .008-.010" is fine for general service.

[Bruce2]

Paul, I think you nailed it. When I was pressing the 3-4 hub back on, I noticed the splines were much tighter than any other ones I've built in the past, and It took a lot of force to seat it. I must have bent the clip like you suggested. 3rd gear's endplay was very low, so backing the hub up a bit will even things out.
I guess there's no harm in having the 3-4 hub able to "float" on the splines???

Marc, I'm a non-believer in minimum endplay like Gene recommends in his writings. I know a drag racer who drank that Kool-aid and eventually figured out it didn't work. At one of our local tracks the staging lanes are down hill. With his car, he had to push it down the hill, while another VW racer had to hold the car back. The problem was all the gears were gaulled together slightly.

[Pablo2]

Center the hub now and it will stay centered .. at least with the 091 circlip mod. (I don't fully trust the 002 circlips.)

Many of us learned the hard way that Gene's theory on idler clearance was off. With trepidation, I tried .003" for 1st & 2nd in my drag trans (1986), and it was a FAILed experiment. Just an extra .001" makes all the difference. For anything other than dragrace, I've gravitated toward choosing the high side of suggested idler side clearance range .. especially with 002 & later.

[Marc]

I've never had any problem with .004", but I also grind some reliefs to allow oil to circulate...even that might not make .003" viable (at least not with conventional lube).

[Bruce2]

....... the late hubs/gears do require more oiling clearance than the early 113 type. ..

Paul, did you discover this by observations?

The factory procedure agrees with this. The spec for early gears is .10-.25mm, but for 002 3rd gear they say .15mm min.

[Pablo2]

I noticed early on that the factory provided more clearance with 002 than with 113 .. and in years past, I've received feedback from builders who preferred .010" on 091 & later gears.
4th gear doesn't get enough cooling oil as it is, so tight clearances are a gamble.
Anyhow .. it's common to press too hard on the inner circlip. I usually have to recenter my hubs, even with the thicker circlips.

[dangerous]

The factory 'method' is to press the main shaft lightly back against the second circlip,(toward 4th gear)
since this is where it will thrust to under load anyhow.

I am sure this method is in one of my Bentley manuals.

Using this method will, more often than not,
mean that 3rd idler has excessive end clearance, and 4th gear, not enough.

For this reason, every 002 main shaft that I assemble,
gets the mods that use the 091 hub circlip. (even dead stock rebuilds)
I have lost count of how many burnt thrust faces I have seen on 002 4th gears!

Sometimes I fit the thicker 091 hub clip, only on the 4th-side,
if the end float of 3rd is correct with the factory thin clip,
but usually it is both sides that are modified.

This way I can control the end float of 3rd idler
(for me, never more than .010". and never less than .006"),
but then 4th has too much, and will require the bearing shoulder machined.

Once I machine the main shaft bearing shoulder, to set the end float of 4th gear
(usually about .010" or so, to correct it),
The final step is to fit an old bearing,(for a width gauge)
and re-cut the circlip groove to 4mm wide.

I use two 3rd gear pinion-circlips to retain the bearing.
(to make a snug fit I can select a pair that have the correct width)

All good trans-parts-suppliers will have the various thickness 3rd-pinion circlips,
but good-used will work fine, for sizes that are not available new.

[Bruce2]

Dave, that's the solution I came up with prior to starting this topic. But not having a lathe makes it more difficult for me.
Yesterday I spent some time with the mainshaft. I was able to center the hub to get just over 0.3mm of endplay on both 3rd and 4th. I think that's where it will stay.
While working with it, I found some thicker clips that I assumed to be the 091 clips mentioned. But when the hub was pressed on, there was well over 1mm of endplay on 3rd, so the ones I have must not be 091 clips. I assume the diameters of the 091 clips are the same as Type 1, so what's the thickness of the 091 clips?

Also, what's the way to get the Type 1 clip onto the 3rd gear side of the splines once you take it off? Every time I tried to put it on, it ended up flopping around, being stretched too much to clear the splines.

[dangerous]

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.

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.

I never remove the clip on the 3rd gear side until/unless I need to,
since they stretch so easily,
although the 091 clip stays in shape so no problems with that one.

The 002 clip can be fitted carefully, with minimal stretch,
by aligning the ends of the clip with the spline,
and keeping it square.
but I think the factory 'wound them on' as a manufacturing step, and they cooled/shrunk in place.
I have never been able to refit one that was as tight as the factory fitment.

You can use a spirolock, of which weddle sell thicknesses that are the same as the '002' one.
These wont solve your end play problem, but they would be tight in the groove.

[dangerous]

The spirolocs that I spoke of from Weddle are
1.55mm thick for the 002, part #9005
and 1.25mm thick(so you need two) for the 091, part #9007.

They have a smaller OD in case you use the small bore aftermarket gears,
but if the 1.55mm is correct,
that may be enough to tighten up the axial movement on the hub.