General Build Questions, good stuff and bad stuff you see

[Casting Timmy]

I just got in a box from someone and have no idea where it came from or who built it and honestly it doesn't matter, but it got me to thinking what good and bad things have you seen from rebuilding? Tricks and set ups and just general weirdness.

Silicone on the Input shaft coupler Snap Ring – not a fan

Bus Flanges Seals
Very loose, usually push in my hand so I glue them in.

Big Pinion Nut
I just got a box in with sealant or glue that obviously oozed out from above and below the nut, I had to cut it off.

Third Gear Clips
I know some double clip, I have done this in certain applications. Usually I just do one tight clip, sometimes I do cut third though to give a flat surface as I have seen a few also chamfered where the clip goes.

002 Shuttle Selector
I have put the 091 shaft into 002 boxes and sanded down the selector so it had full range again with the E clip in place. Recently I saw a box where the pin had been cut up top for an E clip, do you guys do any mods like this?

Shuttle Bracket Reinforcement
I’ve seen 091’s with a full length of metal welded to the side, 091’s it’s more of a ~5/16” wide strip and 002’s can go taller with ½” as they don’t have the metal bracket for springs.

Diff Bearing Preload
How much turning torque are you running, lately it seems like I only do 002’s and 091’s. Been following more the distance method which allows light wrench movement to check the backlash after locking the pinion shaft. I prefer to set up by the numbers when I can and then run “grease” as my double check and to spot the consistency of the pattern around that way.

I should mention I build mainly for the street, or 90% street and 10% off road boxes as they have a big buggy club here in town.

[Pablo2]

Good post, but pictures really help in a thread like this.

"Silicone on the Input shaft coupler Snap Ring"
I agree this sounds silly. A new circlip is all that's needed.

"Bus Flanges Seals loose .. glue them in?"
I suppose, if they seem loose .. I don't run into that issue very often. But then, the last half dozen boxes I've built use the pre-assembled Peloquin steel side adjusters with 930 flanges. https://www.thesamba.com/vw/gallery/pix/1098167.jpg

"Big Pinion Nut sealant or glue"
Stock nuts? Use a NEW one and peen it. For chromoly nuts, Loctite is the norm, as there's no way to effectively peen them. I've used the tiny pin method before ( https://www.thesamba.com/vw/gallery/pix/1670230.jpg ), but gone back to using Loctite. Simple. The problem of chromoly nuts sometimes seizing is because tiny swarf wasn't properly removed from the threads, or the last thread barely hanging on wasn't cleaned up.
https://www.thesamba.com/vw/gallery/pix/1353654.jpg https://www.thesamba.com/vw/gallery/pix/1353653.jpg

"Third Gear Clips .. double clips etc"
I just use the proper thickness circlip, and shoot for “zero” clearance. Once in awhile, a thin shim is required, but this is rare.

"Shuttle Bracket Reinforcement"
It's wise to strengthen this bracket as they often crack at one of the bolt holes. It's also a good idea to retain the ball bearing somehow, so you may as well combine the two upgrades. https://www.thesamba.com/vw/gallery/pix/1023718.jpg

"Diff Bearing Preload?
How much turning torque are you running .... Been following more the distance method which allows light wrench movement to check the backlash after locking the pinion shaft. I prefer to set up by the numbers when I can and then run “grease” as my double check and to spot the consistency of the pattern around that way."
The above seems to be combining two or more steps into one. Diff bearing preload is measured before the ring gear is even mounted, or before pinion is installed. (After all, how can you check diff bearing turning torque using only the backlash distance? You can't.) I've backed away from the factory turning torque method (which often results in excessive preload) and gone back to simple math based on 2mm thread pitch of adjusters. For street use, proper bearing preload is 1.26” beyond “zero” for each adjuster. Pinion bearing preload and R&P mesh are 2 different and addtional steps.

With pinion depth (and bearing preload) correct, bluing check is done with .006-.007” backlash. I've never substituted grease for Prussian Blue, which I evenly apply by rolling a Q-tip on the teeth. I use two different steps to this, first a bluing transfer reading and then a bluing imprint reading. Final imprint reading, drive & coast of ring gear: https://www.thesamba.com/vw/gallery/pix/1178901.jpg
https://www.thesamba.com/vw/gallery/pix/1178900.jpg

https://www.thesamba.com/vw/forum/viewt ... p?t=568039

[Casting Timmy]

I worked at Permatexfor a little bit, the Prussian Blue came to us in 55 gallon drums and was the only thing we pumped out in a little building made just fro the drum and pump. Looked likea little out house on the production floor, they got tired of trying to clean up messes from that stuff and the pump. The whole inside of that room was blue!

You're right I combined two things with the diff.

What kind of preload did you run for race only?

Thanks for the great reply.

[Pablo2]

By "race only", do you mean "diff only"?
As is typical, these questions come up when I'm far from my parts, books, and notes. I have only my laptop with me. But I did the math for the bearing size, desired preload, and the adjuster's diameter and thread pitch. I came up with 1.26" (measured in an arc) as being the proper preload. 1.25" is obviously close enough, and easy to remember.

For a short time, I used the factory method and tools as per Porsche 915 (which uses the exact same Type II bearing) to attain 26 in/lbs turning torque.
https://www.thesamba.com/vw/gallery/pix/1173371.jpg
.. it should be noted that the display of the right hand gauge in the above photo is an actual "in movement" measurement, only possible if zeroing the gauge while in motion. Turning torque measured "from stationary to moving" will read higher than actual.

Anyhow, the factory method resulted in too great of a preload for street transaxles. I don't have a definite explanation as to "why", but I suspect today's slippery oils are not compatible with the old method of measurement. Maybe someone else has some ideas on this ..

Sufficient preload is important. The main case actually expands and leaves the diff slopping back & forth if there's insufficient preload. On the other hand, too great a preload can prematurely wear the diff bearings. One way to eliminate any guesswork (and make your off-road race trans a lot more bulletproof in the process) is the use of a steel plate that eliminates case growth. But the machine work and installation of this plate takes almost a day by itself .. only worthwhile for a serious off-road transaxle. https://www.thesamba.com/vw/gallery/pix/1105843.jpg

Another way to avoid occasional excessive case growth is to cool the transaxle oil. We're doing this in our heavy, horsepower-boosted Syncro Vanagons that spend hours highway driving at speeds far higher than original design intended (as outlined in the final link I provided yesterday).