Hand Packed bearings and slick shift

[Henryhoehandle]

I really cannot answer for the ZF but we have had very good results with the factory 094 4 spider diffs. We all run them hill climbing and they are tough. You have done a lot of excellent work...congrats.

[Pablo2]

Yes, the Weddle gears now register their side clearance off the synchro cone, rather than the center hub. There's nothing wrong with this .. I rather like the arrangement. The splined cones obviously should be removed from each gear and all protectant (coating) removed, so that clearance is properly measured. You say your clearance is on the high side .. Good. There's too much emphasis on tiny clearances, IMO.

The hub you selected is of early round corner vintage ('86-'88), and isn't much stronger than the square corner version. I could be wrong, but I doubt the Weddle part is chromoly. I think it's more likely a case-hardened part, EN36 of some type. Either way, it's far better than any of the factory pieces, even the nitrided one.

I cannot show you a picture of a modified shift rail, as the nearest parts pile is 75 miles away. But this should be standard procedure in any 091 performance trans, whether drags or off-road. In drag racing, the 1st/2nd shift rail will "bounce back" because of speed shifting. In off-road, rough terrain is a further contributing factor to "bounce back". For drag transaxles, I always used the Berg style conversion for enhanced speed-shifting capabilities etc, which of course made these "hybrid" rather than 091. No, the detent doesn't need to be made deeper. But there needs to be a slightly sloping path from the 2nd gear detent toward neutral (actually entering the neutral detent), and stronger detent springs should be used.

Perhaps Bruce will give feedback on the 091 ZF strength. I think of the 091 ZF as a "street only" diff.

[Pablo2]

One last comment, since you will be racing this box soon .. Do not feel you must slam gears when shifting. Ham-fisted drivers break parts. I've always told our Porsche dog box customers that "It's in the wrist, not in the fist." In other words, rapid controlled shifts, yes ... superman "slam 'til it stops", no. This could be the difference between a shattered 3rd/4th slider hub and one that lasts awhile.

[Henryhoehandle]

I agree.. I used to race type 1 late irs with no shift modifications and the synchros would always last until I broke something else. (First gear, diff section). The fastest I ever ran was 4.19 in 300 ft sand drags. I never tried to "speed" shift it as consistency was all that mattered.

[Pablo2]

In going back in this thread, I see mention of modifying slider for deeper engagement, but no mention of corresponding modification to detent location. Detent mods are something I always did after the first trial assembly, in which the difference is measured between full engagement, and the position the stock detent grooves hold the slider. The new detent groove is perhaps 0.010" deeper than stock, and must have proper shape, checked with a loose detent ball. The fact that the entire detent groove is wider is of no consequence, so long as the new spot that the ball sits is clearly defined.

[fastback]

Yes that must be done.
Did this mod on 1/2 rail in this tranny.
When i have converted the 5 speed 094 into 4 speed / 091
I used 002 rails and macined the grooves
As these have shorter stroke

[fastback]

I really cannot answer for the ZF but we have had very good results with the factory 094 4 spider diffs. We all run them hill climbing and they are tough. You have done a lot of excellent work...congrats.

Thanks Henry
nice with positive result from the "VW superdiff"

[fastback]

comparing the spider gears of a ZF and a stock diff, i se the big differneces in size.
091 stock at left , ZF at right
but as we disussed earlier regarding R/P ,big maybe not always same as stronger
the smaller ZF spiders are inside housing that seems pretty strong, so aslsong as they stay in place, they seem to hold up nice.

[Pablo2]

Excellent that you modified the shift rail detents ..

The stock 091 side gears and spiders are quite stout. On the other hand, the ZF ones break without all that much abuse. When we designed our own early LSD, we plugged in the largest side gear and spider gear teeth that would fit .. 930 size. Comparison of ZF and GT : http://images.thesamba.com/vw/gallery/pix/1221085.jpg

[fastback]

If all goes well i'll find out the real strenght of the zf.
Hoosiers is on and launch control will be tested.
Poor poor tranny....

Regarding gear clearance i get that a higher axial play wil allow more oiling
But in a drag only tranny where strengt maybe highest priority i asume a tighter clearance will give the gears better "support". As there will be less movement .??
Always compromises

[Pablo2]

The gear will always be thrust to one side during acceleration. Any clearance that is so small as to counter "helix gear c0ck" would most certainly also be too small to allow adequate lubrication. Anyone who's followed the Gene Berg instruction manual for a drag trans has learned this the hard way. 1st gear exhibits the worst gear c0ck, so I got brave once and set 1st gear clearance to just under .003". Big mistake .. fried thrust surfaces. You can get away with loose needles in a drag trans, but leave adequate side clearance for oil.

[Henryhoehandle]

I hand packed the needle bearing in mine in 1st (weddle gears) and I have only had it apart once in 6 or 7 years and it still looked fine. But, the again, this is mostly and off road trans that occasionally gets driven on the highway for short (30 miles or less) trips so the box does not see high temps. It is probably not the best idea to hand pack for long distance trips, but this might be debatable as well. No doubt it allows for less cocking of the gear. I agree with the end play...better to have a little more then not enough.

[Bruce2]

Perhaps Bruce will give feedback on the 091 ZF strength. I think of the 091 ZF as a "street only" diff.

I've only had about a dozen 091 ZFs pass through my hands. One friend installed one in a fairly high hp street car then took it to the track on slicks. The car wheel hopped badly and blew up the spiders. I heard of another 091 ZF owner who did the same with a street car.
The problem is the tiny spiders. They can't take the impact. The 091 spiders are the same part as the Type 1 IRS spiders, and those spiders are a LOT smaller than the normal Type 1 open diff. If you want it to survive, add clutch discs. Then they take more of the load than the spiders. You can also substitute Type 1 IRS ZF pressure rings so they clamp tighter onto the 091 discs.
I don't know if you can get discs from VW. Since you are in a country where VW sold 091 ZFs, your local VW dealer may be able to get discs for you. Please look into this, then let me know and I'll buy some from you.
The sandrail guys like the 091 ZFs. I've had a few very happy buyers in that crowd. Turning brakes are a big NO-NO with a ZF, though.
Finally, the Bus guys who do light off-roading like ZFs too.

[fastback]

thx for sharing your experience bruce.
I asume the 091 and 094 ZF are the same diff/partnumber . (mine is from a 094 5 speed)

wheel hopping kills a lot of stuff

BTW how is your guys experience in case strenght?? :
3 rib vs 5 rib vs 6 rib?
I always used 5 or 6 rib cases for my builds but have a lot of 3 ribs also and some 091 parts i would like to test out.
from what i have heard the 5 and 6 rib is pretty equal in strenth. but how much weaker is the 3 rib?
i asume case brekage/flexing is not as big problem as with type 1 cases

[Bruce2]

091 and 094 gearboxes take the same ZF.

I have zero experience with bus 'boxes. However, Dave Folts told me once that the 5 rib case is just as strong as the 6 rib, and it's lighter.