Supplying Lube to 4th Gear

Discuss VW transaxles and transmissions. Gearheads wanted!

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Dougy Dee
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Supplying Lube to 4th Gear

Post by Dougy Dee » Thu Sep 21, 2017 7:54 pm

An early 90's SYNCHRO trans was brought in the other day. No 4th gear.
Teardown developed a large and expensive list of destroyed parts. These included a destroyed MS brg. (I'm not sure whether 4th gear wore the groove in the MS Brg inner race or vice versa...)
A destroyed Main Shaft due to fretting on it's 4th gear brg race and a damaged pinion head from pieces of 4th gear going where they weren't designed to go...
The grenaded 4th gear was missing enough teeth to call Arkansas home and also showed signs of fretting due to lack of lubrication.

Yes. Another conversion camper with non T4 power. This one a TDI conversion. The Subie conversions are just as bad. Needless to say all the parts are gonna be fun to locate.

I've had the pleasure of repairing several of these (3, 5 & 6 Rib) recently. All with the same problems.

I'm wondering whether there is a way to supply pressurized lube to the MS Brg/4th gear area?
I am considering drilling and tapping for supply and adding a port thru the gear carrier to supply gear oil to this area.

Does anyone have first hand experience with a pump that will stand up?

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Pablo2
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Re: Supplying Lube to 4th Gear

Post by Pablo2 » Fri Sep 22, 2017 9:23 am

I've been oiling 4th gear idler on some applications since the late '80s .. first with our Elephant intermediate housing ..
https://www.thesamba.com/vw/gallery/pix/1079085.jpg

.. and more recently with my SVX-powered Syncro Westy:
https://www.thesamba.com/vw/forum/viewt ... p?t=568039

I'm presently helping in the development of a billet intermediate housing that will supply oil to this area in a far more professional manner than my efforts in the above thread. There will be a number of features to this housing that will hopefully eliminate this "weak link" to the Syncro transaxle.

Also in the works (being cut right now) are Syncro mainshafts which have been gundrilled, supplying oil to 3rd & 4th needle bearings, as well as the mainshaft needle bearing. (This needle bearing really should be changed out for the earlier 113 bearing with larger needles.) These mainshafts / 1st/2nd gears will feature the same Formula 1 gear profiles as our GT 3rd & 4th gears, and should live considerably longer than OE equipment.

All of this was prompted by my own use of the 230 hp SVX engine in my heavy Syncro Westy. The TDI presents challenges that may be beyond mere horsepower and torque.
aka Pablo, gears, Geary
9.36 @ 146 in '86

Dougy Dee
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Re: Supplying Lube to 4th Gear

Post by Dougy Dee » Sun Sep 24, 2017 2:07 pm

Thx greatly for the info and link. I recall scanning thru the Samba link a while back but forgot which site it was on...

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Pablo2
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Re: Supplying Lube to 4th Gear

Post by Pablo2 » Sun Sep 24, 2017 3:45 pm

Regarding the wear you see on the mainshaft ball bearing inner race:

This odd wear is exhibited almost exclusively in heavy Vanagons having engines with greater horsepower and torque than the original stock 2.1. I'm not sure why the harder bearing material sees the majority of the wear, but that is most certainly the case.

The wear is NOT from the spinning motion of the idler against the thrust surface when not in 4th gear, but rather the wear occurs while the idler is "theoretically" stationary against the bearing race. Examining the wear pattern confirms this .. wear is not circular, but rather it is "splotchy".

What actually causes the wear is an orbital resonance of the idler and the "smearing" of the two hard surfaces. Two main factors contributing to this orbital motion: 1) The helical design of the gear pair, which "cocks" the idler gear 2) The necessary bore clearance (which keeps the internal needle bearing from seizing) also allows cocking of the idler. The greater the clearance, the more the wear.

This issue is exacerbated by the TDI engine, which delivers torque like a sledge hammer, especially if using a heavy foot at low rpm.

Additional oiling probably WON'T cure this issue, unfortunately. A straight-cut gear would reduce it somewhat, as would running the idler on a bushing, rather than a needle bearing.

Fortunately, the wear isn't a real problem, in that it doesn't lead to a shorter life expectancy of the transaxle. The only real result is greater side clearance of 4th idler gear. Other things in the transaxle will go south long before this bearing wears away.

What oiling 4th gear WILL do is to 1) reduce heat generation at the second most critical area (R&P and pinion bearing being the most critical), and 2) hopefully wash away metal particles generated by the orbiting before they cause too much damage to the mainshaft bearing races and balls.

Anyhow, you might want to PM me for some of the parts you need. Syncro bits are becoming extremely hard to source.
aka Pablo, gears, Geary
9.36 @ 146 in '86

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doc
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Re: Supplying Lube to 4th Gear

Post by doc » Mon Sep 25, 2017 7:05 am

Pablo - Super write up!

doc

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Pablo2
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Re: Supplying Lube to 4th Gear

Post by Pablo2 » Mon Sep 25, 2017 9:35 am

Thanks, Doc ..

Dougy, the other issue you see on the mainshaft (aside from an overheated and smearing 4th gear) .. the "fretting" marks .. this is called "false brinelling", and is the result of the hammering action of the TDI engine on 4th gear, specifically when the driver is attempting to maintain speed at too low an rpm. It's natural to want to use the maximum capability of a diesel engine, but the expense of this habit is the eventual destruction of your puny VW gearbox.

A compromise can be reached which will minimize this issue, by maintaining a higher rpm while cruising. In other words, DON'T get carried away with using too tall a gear ratio for 4th gear, and don't "short shift".

False brinelling is often reported in gas engined vans too, when a "transmission oil" is used, instead of a "transaxle oil" (thin synthetic GL4s vs thicker dino GL5 oils). I don't want this discussion to devolve into an oil debate, but the feedback is clear. In this case, it seems to only happen when the vehicle is driven on the highway for hours on end.

Hopefully, our oil-drilled mainshafts, which deliver oil to 3 points along the mainshaft, will help with this issue. Since false brinelling occurs while the needle bearing is stationary, oil delivery to the gear needle bearing can be beneficial, even if the gear isn't spinning.
aka Pablo, gears, Geary
9.36 @ 146 in '86

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