mk1-forum.net

Hi,
Rebuilding a 4 synchro pre A+ box. Have read and reread Haynes manual and can't see recommended endfloat. Got more confused watching Youtube videos of rebuilds. [ box came apart with a 005" shim]. Should endfloat be measured without any shim and the retainer nipped up against the bearing and what number should I aim for?
Thanks, D

Just lightly nip the 3 or 4 bolts (depending on box) up with no shim, measure the gap and add shims until the gap is taken up, some say a preload of .001 is desirable. That's how I have just done mine, rightly or wrongly but am sure someone will be along to inform me I'm wrong or right!!! That's where I had a problem with my box, too much preload I think.

I know what the workshop manual says and IMO, it's not right. You need to lock the bearing in tight. I rarely use any shims at all. With any float of movement, all that's going to do is wear the tunnel in the case.

Manual says you need pre-load, not end float.....about 1-2 thou pre-load.......

Nip up the bearing carrier (just finger tight) with no shims, measure gap, subtract 1 to 2 thou from that, and, you have your shim thickness, which, will give you the correct pre-load.....If you measure 6 thou, take, 1 or 2 off that, and, you can use either a 4 or 5 thou shim.....

I usually go for closer to 2 than 1....

nipped up bolts on retainer(finger tight), no shim- got tight 004" clearance between retainer and bearing ( old shim is 005" thick). Getting confused again!

davidmuir wrote: ↑Fri May 21, 2021 10:46 am nipped up bolts on retainer(finger tight), no shim- got tight 004" clearance between retainer and bearing ( old shim is 005" thick). Getting confused again!

You mean between the retainer and the gearbox housing??? so if you have .004"gap at finger tight/nip up. I would try the .005" shim as by the time you tighten the bolts properly it'll pull in some more or you can get some decent quality wet/dry on a flat plate and rub the back of the retainer and sand off .003" which would then give you .001 preload. That's what I have done when I've not had the correct shims to hand and it's worked fine.
Then just check everything turns freely and the syncro hubs are looses too

Okay, all together now with 005" shim. Wouldn't say that everything is spinning freely- have read that this can improve once everything torqued up.

That will give you a couple of thou loose.......It will allow the bearing to spin in the case, and, may (probably will) cause wear in the case where the bearing sits.....

If you measured .004, you should take .001 to .002 off that.......Correct shim, would be .002 or .003

The whole reason for doing this, is, to lock the outer bearing race solidly to the gearbox casing, so, it doesn't wear the casing.....It really has nothing to do with end float per se, other, than, you are trying to eliminate the end float, at the bearing/case interface......

Indeed you are right but how much does the difference between nipped up by hand and torqued up to the correct spec make?? .002? .003? Best just to flat the back of the retainer plate if you want to take out .001"
I have never known the bearing to spin ever, in all my days racing never seen it, nada.

The shims applied here don't preload the Bearing, they only are used to hold the bearing in the case. Regardless how tight of loose it's fitted, the Bearing Assy, will always have the same Preload applied to it as that's set by RHP (or who ever made the Bearing) on the Inner Races of the Bearing when they are made.

The factory Figures are + 0.001" nip to 0.001" float.



If you look at that sketch above, you can see the Outer Race of the Bearing is 1 piece, but the Inner Races are 2 separate pieces. It's the fit between those 2 inner races that determines the Bearing's Preload.

Also, the table above has the Shim Table and if you do the maths on it, you'll see the Factory says 0.001" float here is OK, though IMO, they should be locked tight.

MrNoo wrote: ↑Fri May 21, 2021 11:18 pm Indeed you are right but how much does the difference between nipped up by hand and torqued up to the correct spec make?? .002? .003? Best just to flat the back of the retainer plate if you want to take out .001"
I have never known the bearing to spin ever, in all my days racing never seen it, nada.

In the early Cases, yes, I agree here, but in the Rod Shift Cases, especially the later ones, I have seen lots that have. I have no file photos, I'll try and post some next week when I'm back home.