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Help setting up a used gear set in a manual transaxle
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jordauto
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PostPosted: Wed Mar 03, 2021 4:59 pm    Post subject: Help setting up a used gear set in a manual transaxle Reply with quote

Hello all. I'm hoping for another set of eyes with more experience in these transaxles than I have. I'd like to hear from any of the trans rebuilders out there.
I've read through all the trans rebuilding posts I can find on here and they all seem to be for setting up new gear sets. I realize that used gears can be more challenging to set up, especially getting them to run quietly. My ring and pinion look good and made no noise before disassembly.I have experience rebuilding automatic and manual transmissions as well as conventional differentials in rear wheel drive vehicles. I've been a licensed auto tech since 1992, and I've never had any problem setting up gears before. This trans was rebuilt by a highly regarded rebuilder a few years ago and only has 90,800Km or about 55,000 miles on it since then. It started making noise at all speeds and didn't change with load or coast. I assumed the worst. My biggest mistake was assuming the worst and tearing it apart without checking backlash and gear contact pattern. Turns out the only failed part was the small end pinion bearing. I'm replacing every single bearing and wear item while I'm in there and adding oiling plates and upgraded bigger roller bearings in some of the gears. Its a 4:86 ratio and had a .70mm pinion shim in it. Both the main housing and gear carrier were sleeved at the time of the last rebuild. I can get a reasonable pattern on the coast side, but not the drive side. I am applying load to the carrier while turning the pinion to check patterns and have the correct pinion bearing and side bearing preload. I have checked each shim change at .006", .008", and .010" backlash. The pattern never changes much with backlash change so I'll just show pics at .008" backlash.
So here is the .65mm shim and backlash at .008"

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Next is .70mm and backlash of .008"

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And .75mm shim and .008" backlash
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This is the home made brace (VW381/8 ) to keep the housing from spreading when setting the side bearing preload.

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And this is how I am applying load to the carrier when checking contact patterns.

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I have tried the .80mm shim and still no better pattern on the drive side, but the coast side is too high up the crown (peak) of the gear and biased towards the heel and backlash won't bring it back to an acceptable pattern. As far as coast side patterns go, I'd say the .75mm is pretty good but the drive side is not what I'd expect to see. Long, long ago during my apprenticeship I was taught to pay more attention to the coast side pattern with used gears but I really want to make sure I get this right the first time. Oh, and if you noticed the locker, its not a syncro, it's a 2wd with a locker added.
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MarkWard
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PostPosted: Wed Mar 03, 2021 5:05 pm    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

Backlash is adjusted by the side rings not the pinion depth. I’m assuming you marked the side rings and measured the depth before you removed them? If not, your kind of jammed at this point. Report back.
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jordauto
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PostPosted: Wed Mar 03, 2021 5:32 pm    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

Hi Mark. I didn’t mark and record the side adjuster positions as all bearings have been replaced with new. I installed the pinion with its new bearing and a shim. Then use a dial indicator to measure backlash as you would with any differential. For side bearing preload I set up my backlash and then turn the side adjuster on the starter side in the 1.26” method.
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PostPosted: Wed Mar 03, 2021 6:08 pm    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

Normally new bearings or not always mark and measure the side covers. So, you really should measure and correct the differential bearing preload. The easiest way to set it is with the ring gear off. You try to equally turn the rings in till the bearing preload is set. Mark that point. Going forward you will then move the side rings equal amounts to get your back lash while maintaining preload. Of course that is after you reinstall the ring gear. Example, if a ring is turned in a 1/4 turn, the opposite ring is backed out a 1/4 turn. This moves the ring gear on and off the pinion gear tuning backlash while maintaining preload on the carrier bearings. Pinion depth is what the case shim accomplishes.
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PostPosted: Wed Mar 03, 2021 8:00 pm    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

man, i'll tell you what....

i'm all for home made tools but i think it's suicide to use that home made brace. i've done enough of this work and what i can tell you is the vw brace is VERY precise to keep the case from spreading. as in so precise if you try to drop it on the pins with the diff unloaded and you go on just a hair crooked, it will bind. once preload is set it's kind of hard to remove.

you may get lucky with that home made arrangement but personally i wouldn't trust it.
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jordauto
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PostPosted: Thu Mar 04, 2021 10:26 am    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

Ok, so I'm not the greatest at communicating especially when I'm trying to put thoughts out through the keys on my laptop or even worse the virtual keys on my phone. In trying to condense my original post so it would be short enough that someone might actually read it I omitted some details that I thought would be assumed. I'll address those criticisms now. So I did not mark the side bearing adjusters, but they were marked from the previous rebuild. I used a yellow paint mark pen to highlight the marks as there was more than one set before disassembly. Most likely from previous rebuilds. My core was not usable when that rebuild ws performed and this trans was built for me from parts on their shelf.I didn't pay much attention to the side adjuster marks as I knew I would be replacing all bearings during my rebuild process and possibly the ring and pinion. Replacing either carrier bearings, big pinion bearing, or gear set makes the original backlash and preload settings irrelevant and requires going through the set up procedure. There is a chart in the trans section of the Bentley that backs up this thinking. So again my process was to press the big pinion bearing onto the pinion shaft, torque on the 1st gear inner race/ nut, check. the turning torque against the spec in the Bentley, install it into the main case with the .70mm shim that was in it previously as a starting point. Install the pinion nut and torque to the 162ftlbs. install the differential assembly into the case, snug up the adjuster rings by hand to support the diff. Install the brace ( I'll get to that in a sec), and dial indicator. Adjust the left side adjuster to get the desired backlash and snug the right side adjuster to remove any play and then turn it in 1.26" measured in an arc to give the bearing the .006" of preload or crush if you will. This method has been well discussed in this excellent and detailed post. Starting on page 11 and more detailed info on page 12. https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

And to answer questions of the home built VW381/8 brace, the bottom web is 1/4"x 1" flat bar, the side web is 1/4"x 3/4" flat bar, bent and welded together. The pieces that drop over the dowels are 3/16"x 1" as I didn't have any more 1/4" scrap laying about. I didn't have a drill bit that would provide a friction fit over the dowels, so I used the next size down and used a fine sanding drum in the Dremel tool to ream them until they can just be pushed over the dowels by hand with some force. I set the whole thing on a core trans housing I have laying about and used that as a jig to tack weld the brace together. With the side adjusters slacked off the brace has to be pushed down onto the dowels. the bolts are installed with a couple of washers for backup. I tested it before trusting it. The dial indicator was rigged up from one side of the case to the other and the side bearings brought up to preload using the above method and there was no deflection recorded on the dial indicator. I'm pretty confident that it is doing its job.
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PostPosted: Thu Mar 04, 2021 10:36 am    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

So, what is the problem then?
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PostPosted: Thu Mar 04, 2021 12:00 pm    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

As I thought I stated in the original post I would like another set of eyes with more experience setting up used gear sets in these to have a look at my contact patterns and hopefully share some insight on the patterns I have so far. New gear sets are easy and you can get a good pattern every time. But used gears are more of an art form and less text book.
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PostPosted: Thu Mar 04, 2021 12:13 pm    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

The .065 seems to have nice depth. The .070 looks to be a good average between the two. ,008 backlash seems tight for a used ring and pinion. Sorry not much help.
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PostPosted: Fri Mar 05, 2021 11:25 am    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

For the best chance of a good drive pattern, stay with original shim of .7 and increase backlash to what is typical of a used R&P, .010"-.011"
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PostPosted: Fri Mar 05, 2021 12:31 pm    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

If it helps this is my pattern after user gears sorted me out. 0.70mm and playing with the back lash. I also played around with the method to apply 'load'. I think I settled on jamming a piece of wood between the case and the diff. Changing up the load method help with the paint pattern, you can actually see it change in the various pictures.

Disclaimer: It was my first time doing any of this.
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PostPosted: Fri Mar 05, 2021 5:36 pm    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

Thanks all for the help so far. Old man, I read through your entire trans build thread before starting mine and it was definitely part of my motivation for wanting to attempt doing this in house rather than have to pay the $300+ each direction for shipping to the states. So I had a few minutes to try again. At Gears suggestion I put the .70mm pinion shim back in and increased the backlash. I went up to .012".

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This is what that looks like. I used the block of wood in the press to apply some drag to the carrier. I would estimate it takes about 15ftlbs to turn the pinion with the load applied. I'd like more load but haven't found a better way to load it yet. I included a pic of the pattern on the drive side of the pinion as well. You can see that the contact is mostly along the peak of the teeth. Using a mirror and checking the coast side of the pinion shows a nicely centred pattern almost the full length of the teeth as you would expect from looking at the ring gear pattern. I like the coast pattern as it sits. But that drive side is a mystery. Such a narrow pattern and at the increased backlash its starting to creep towards the heel.
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PostPosted: Fri Mar 05, 2021 7:15 pm    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

Out of curiosity, what are you spinning? Are you turning the diff or are you turning the pinion to get your wear pattern?
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jordauto
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PostPosted: Fri Mar 05, 2021 7:26 pm    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

I’ve tried both. But spinning the pinion is the way I was taught ages ago during my apprenticeship. So I’ve been turning the pinion to check my patterns.
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PostPosted: Fri Mar 05, 2021 7:57 pm    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

How about a picture showing a few unpainted teeth so we can have some idea of what the existing wear on the teeth is like. From what I can see in this photo where the unpainted teeth are out of focus, it looks to melike the gears may not have been set up well previously or were damaged by the pinion bearing failure.


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Last edited by Wildthings on Sat Mar 06, 2021 8:51 am; edited 1 time in total
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PostPosted: Sat Mar 06, 2021 8:20 am    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

jordauto wrote:
This trans was rebuilt by a highly regarded rebuilder a few years ago and only has 90,800Km or about 55,000 miles on it since then. ....Turns out the only failed part was the small end pinion bearing.


I'm curious about your pinion bearing.
A new pinion bearing should still be tight well beyond 150,000 miles, even following Vanagon customs of zero transaxle maintenance.
I'd suspect it had a used pinion bearing.
Or worse, a loose bearing that was "tightened up" by hand, on a sander.
Does it have sanding marks on either of the center race interfaces?

Image may have been reduced in size. Click image to view fullscreen.


This ^^ ABOVE ^^ was the smokin' gun I found in my rebuilt that was deader'n a doornail at 9,000 miles (circa 2011)
The grind marks when the factory "sets the new bearing preload" are not deep and directional, but very fine, and 'centerless'.
And certainly not spilling over to touch the cage.

Link

Or of varying thickness when measured with a micrometer.
This is what is happening inside the trans when the rebuilder saves $100 and puts in a used, hand-sanded pinion bearing.
ALL the preload loads ends up on "one roller" which chews away the race hardfacing, and then starts chipping off all the bearing's hardfacing from there.
It munches down to thesofter substrate, and generating big sculptures on the drain magnet.
Either to save $100 for himself, or because the customer asked for the cheapest 'rebuild'.
Hand-grinding is about the most ridiculous thing imagineable.

The gory details: Syncro transmission rebuild every 10-20k miles
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PostPosted: Sat Mar 06, 2021 11:00 am    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

Hey Sodo. The big pinion bearing was new and still turned smooth and had preload. Zero signs of wear when I took it apart. But if I have to tear the trans down then I’m going to replace everything while I’m in there. No point in going back in later because something else failed. As I stated earlier, the only part that failed was the small end pinion bearing in the gear carrier housing. Gear oil has always been changed yearly which is about 10,000km or 6,000 miles of driving. I’ve only ever seen the slightest bit of metal on the drain plug magnet. I had posted it in the transaxle failure thread some time ago. I posted pics in that thread.
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PostPosted: Sat Mar 06, 2021 11:02 am    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

The failed bearing was the small (front) pinion bearing.

When setting up used R&Ps, it's sometimes helpful to first put a small chamfer on the edge of the pinion teeth with a Dremel. You especially want to do this when reducing backlash.
https://www.thesamba.com/vw/gallery/pix/1109383.jpg
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Last edited by gears on Sat Mar 06, 2021 11:05 am; edited 2 times in total
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jordauto
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PostPosted: Sat Mar 06, 2021 11:02 am    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

Ok here’s a close up of the teeth on the ring and pinion.
Drive side first.

Image may have been reduced in size. Click image to view fullscreen.

Coast side.

Image may have been reduced in size. Click image to view fullscreen.

And pinion gear drive side.

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gears
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PostPosted: Sat Mar 06, 2021 11:14 am    Post subject: Re: Help setting up a used gear set in a manual transaxle Reply with quote

Ring gear appears worn at the edge, where the pattern is showing up. Like Wildthings said .. possibly a previously incorrect set-up.
If I were to reuse, I'd probably end up chamfering the edge, and set @ .010" backlash.
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