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Gearbox assembly question

5K views 21 replies 4 participants last post by  CatellusEng 
#1 ·
Hello,

When re-assembling the gearbox shafts, do the internal splines need any particular lubrication?
My question is related to whether these are lubricated by the gearbox oil in normal use or if there needs to be some moly grease in there beforehand? I don't see a lot of oil ingress paths.



The same question goes for the inside surface of some of the inner races of the gear bearings, the face which sees the shaft might not see much oil as it doesn't move around the shaft.

Thanks.
 
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#4 ·
Richard, thanks again. You were absolutely correct. There is indeed no need for lubricating those. In fact upon more careful inspection I found there are always ways for oil to make its way in there.

Both shafts are now assembled and I have done both nuts up to the right torque but I'm not fully happy with it, I've got two questions:

1 - I have measured the flange to pinion distance before and after, I did not change or touch the main bearings at all and still it's now 0.076mm longer, this is above the stated 0.03mm tolerance. Is this something I should be worried about? Should I now check the pinion to diff teeth attack pattern?

Edit: The measurement was not done via indicator as per the manual, it was measured in a CMM.



2- The main shaft has got some play that I don't remember it having before. I've double checked the torque figures, it doesn't rock back and forth at all but it rocks up and down quite a bit. Is this normal? It could be given it is supported at both ends by needle bearings but this feels excessive to me...
Videos here:
https://photos.google.com/share/AF1...?key=WUs0TFJYNzVfM1J6dVYyNnRQNlJ1endVVEdsLTBB

https://photos.google.com/share/AF1...?key=WUs0TFJYNzVfM1J6dVYyNnRQNlJ1endVVEdsLTBB

Thanks
 
#5 ·
assembly

Yes the additional length will result in noise and rapid wear. Allowance is only .001" or .03 mm.
The shafts are supported on both ends and in 3 places on the main/pinion shaft. The center bearings allow a little movement on their own.

If you have used a non original bearing, tripod, shim, spacer, gear sleeve or gear that will likely be the reason.
 
#6 ·
No, all of those parts came out and went back in in the same order, I only replaced synchro rings and selector rings which are obviously not part of that equation.

The only thing that could have changed is one of the gear bearing inner races being assembled the other way around compared to how it was. I didn't pay too much attention to those.
 
#7 ·
An update on this now that I have tried a few things and repeated the measurement a few times

227.755mm <- Original measurement before disassembly

227.832 <- After replacing syncro and selector rings

227.833 <- After confirming nut torques. Pinion shaft nut did need a little more torque but that didn't make a difference.

227.837 <- Disassembled the whole stack again, confirmed position and orientation of every tripod, spacer, sleeve and shim, one sleeve potentially the other way around. Unfortunately it made no difference.

So after all this I know:
- The measurement is very repeatable and accurate.
- Something is wrong with the stack or the initial measurement came out wrong.

At this point I think I will have to confirm the ring gear attack pattern... I really wanted to avoid this. Any other options left?

Thanks.
 
#8 · (Edited)
Assembly

you should pattern the Ring & Pinion to insure correct engagement. Not so hard to do as the Transaxle should be assembled and torqued together properly. The ring geag can be removed from the right side to see results.

Pics & instructions of such can be found at Richmond Gear on the I-net.
 
#11 ·
No, I didn't, and the backlash pattern looks good to me in fact.

Although let's be fair here I'm still at a loss as to why the pinion length would have changed.

I will measure the shim ring between the flange and 4th and either fabricate a new one or grind this one down...
 
#14 ·
Ok so I've been shaving a few hundreds of mm from the shim ring. The target was to remove 0.082mm, I did it in three steps, first removed 0.03 then 0.06 and finally 0.09mm and patterned the ring gear each time to have a feel for how sensitive it is.

I don't have pictures of the first step, but the following is the -0.06 step:

Followed by the -0.09mm step:

power

coast


I can see it sits much better, not sure if I should remove a little more. What's your opinion?

I am still chasing the reasons as to why the assembly had grown in length but I don't think I will ever know.
 
#15 ·
My apologies for coming late to this thread -- and late to the world of Alfa Romeos! My experience has been 23 years of service to another European marque's transmissions. My thoughts, please take with as many grains of salt as you wish.

Unfortunately the method of bluing will not give you meaningful results. The problem is that taking a pattern as you've done does not simulate how things will actually load up and center under engine load: with the engine pushing one way, the road forces and drive train friction pushing the other. These forces moves the contact center on the pinion and ring gear teeth. When properly measured by the factory (well, the ones I am familiar with) to minimize mechanical noise, the pinion depth is done in a rig that creates load.

Normally my experience has been that, barring particular circumstances, you do not need to measure and adjust pinion depth. The particular circumstances that would make it desirable to measure depth include changing the ring-and-pinion set, machining to the case, or of course some previous service that made a mistake in shimming (and that happens...).

Kudos to you for measuring with a CMM! I hope this is helpful and good luck with the project. It seems (from my brief acquaintance) that getting quiet running of Alfa pinions is a persistent problem.
 
#17 ·
You're not late, you are perfectly on time, many thanks for your reply.

In the particular case of this box, I don't know how it was done at the factory, but I do know that the pinion does come marked with a number (in cents of mm) which can be used to reset the depth to the correct factory value.
However I don't have the tools which would allow me to do this.

Failing that I can only try to reassemble it back to what it was before, a state at I know wasn't producing any noises or anything out of the ordinary.

I did take care to measure it in the most accurate way I could access, thanks to a friendly colleague at work who helped me out.

I was very surprised to see the depth change so much, I have no explanation for that. I did notice the shim was quite heavily marked, it had these deep grooves (I could feel them with my nail) which only went away after I took about 0.03 to 0.04 on each side of the shim. You can still see a trace of it in this photo:


This was a little surprising because the shim sits between the two flat surfaces of the 4th gear inner race and main bearing race as seen here:


I know someone had opened this box before so who knows...

Either way, regardless, the depth is now set to what it was before (within tolerance), the pattern looks okay-ish so I think this will be it untill the car goes back on the road...
 
#18 ·
If this is a 3.0 liter gearbox. They were known for wearing the shim you mentioned in the previous post. It was quite common to see this.

Back in the day. We would go into the gearbox and measure the inside lip. The part of the shim that didn't have any wear on it and order a new shim of the same size.

As to why your measurement change. I don't understand that either. As the parts you replaced would not change the depth.
 
#20 ·
The grooves in the shim are almost certainly because the bearing has spun. Take a look at the walls of the case where the bearing sits: you'll see signs of its turning. If there is still decent interference between the outer race and the case, you can use a bearing / shaft adhesive aka. green Loctite to lock the race into place. Otherwise it is probably best to source a different case.

I have not found a source / alternative for the pinion shims, which I measure to be 61.0 x 70.8 mm. I do have a source for the differential carrier bearing shims. Anyone know of a source for the pinion shims?
 
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