Drag race ring and pinion backlash opinions

[michla]

Running a 3.88 Super Beetle ring and pinion in a gusseted box here.
Did a forum search but don't see it posted yet: what's the opinions out there for minimum ring and pinion backlash on an "all-out" drag Type 1 IRS trans?

Berg Tech Articles mentioned .0000 to .0005 for all out. I have .002 and not the right combination of shims available to reduce it to .0000.

Opinions ?

[jfats808]

Rancho can make custom size shims.
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2276 IDA's 86C 11-1 DD !
2017 48 Trijet DRLA's W125

[spencerfvee]

run it. one can get to pickie when building a trans . I set our gear boxes up for raceing.. from .0002 to .0006 and we run low 10.00s 1/4 mile and the trans lasted 15 years. gene berg told me that he would set the ring gear back lash up tight. then he used valve grinding compound to get the .0000 backlash. by putting the valve grinding compound on the ring gear and running the trans with some kind of small motor .till he could turn the ring gear over by hand I never tried it . I would not put it past Gene to have done it lol he did a lot of crazy things back then lol spencerfvee

[gears]

Few R&Ps mesh well at 0.0. Set backlash to .004", be certain of your preload, and check mesh with bluing. You may need to add .05mm to pinion shim stack for proper pattern.

If you preload drivetrain on launch, normal backlash isn't an issue (assuming no side cover lift).
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[michla]

MAN--there are some fantastic responses here !! Most helpful--you guys are great, keep 'em coming...

Yeah, my preload is per Service Manual (new SC bearings; I have 28 inch lbs). I do load up the trans on the line waiting for the light--always have because slamming the CV's and axle splines is the worst.

Gene Berg was a good friend to me and I took everything he said verbatim considering his experience--I actually was successful at setting up my last diff R&P backlash at .001" without lapping, but that is too funny the part about how methodical he was--and yes, you're right, you knew him well too. Yes, there has to be some craziness in there to justify the perfectionist in it all !

And I like the comment very few R&P set up with that kind of backlash--which is a practical way of saying: NOTHING is "perfectly round" to such perfection--including a ring gear or differential. I'm setting up a Quaife TBD and it checks out fine, but noone can expect perfection down to .0005 given manufacturing tolerances both by Quaife or Volkswagen AG !

[gears]

I remember 30+ yr old discussions of setting up R&P in anticipation of X-amount of 4-bolt retainer flex and side cover lift .. but IMO it's better to just limit this sort of movement. Some food for thought here:
http://www.shoptalkforums.com/viewtopic.php?f=50&t=89944
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[michla]

great read, gears-thx

[michla]

Ok, I got it down to 0.00 backlash. With .002 lash as previously mentioned, I decided to take the trouble to move .002" worth of shim on the right side and add .002" on the left side. Great....
But let me ask this--there is about 20 degrees of rotation that I can feel the ring teeth "overmeshing" slightly (can still turn by hand easily enough but can feel that) and I'm thinking that's not going to do any harm (would NEVER do for a street vehicle--this is pure draggin'), does anybody have any feedback on that? Obviously not everything-differential/side covers/ring gear is perfectly ellipital and/or round, so there's always a little difference in lash from one side of the ring gear to the other.

[michla]

Ah heck..call me crazy, but yeah I lapped my ring and pinion together today using a big, old Milwaukee drill with a cut-off 3/8 extension as a driver and the modified CV cup I welded an old 3/8 drive socket to. Guess I couldn't stand it until it was perfect --taking NO chances here. I've had my share of a transaxle disaster once, not going to do that ever again if I can help it.
So I now have 0.00 backlash.

[CUBA]

[[email protected]]

A well known builder over on the UAC uses 25 inch pounds of rotating force preload on the diff carrier bearings, an .003 for the backlash. The teeth need to have some room for oil.

[michla]

with the heavy load on launch, all oil is squished from the gear mesh anyway--it's the oil before and after gear mesh that cool and wash. A drag car operates maybe a few minutes at a time--much less going down the track.

The rationale for having no backlash is to avoid banging or "hammering" the r&p teeth back and forth on hard acceleration and high loading--which as you can imagine is amplified at insanely high operational speeds. Torque loads on the drivetrain oscillate no matter how much you mash the gas pedal due to inconsistencies in the terrain (track surface) and tire slip.

I wouldn't want to try "driving" a drag car to the grocery store with 0.00 r&p backlash !!

[mark tucker]

ok back from the dead thread.. so what is a good backlash to shoot for for a street driven car, i was thinken around .003 and the heat and expansion would bring that to probably .004-.005. Im at .008-.009 now.(and I hope I have enough shim's to bring it down some.) 3:88 gear. the ring gear has been deburred good, but somehow I just noticed I didnt do the pinion I did the r&p on my colonel klink in bug and must of thought I did the jackie gleeson gear too.....but effing apparently I didnt and just noticed it setting backlash. effing sight&moron opptomatrist that cant do their job any better than I can. and Im not pulling this dam thing back appart.I havent been this pissed in a long time at my self or any body else. so... yes I fucked up.

[Casting Timmy]

I've read 6 as the lowest for a street machine.

[modok]

Yeah .003"-.004"
I set up a few around .004 and they were fine.

I took the "drag racer" advice once and set it up tight, maybe .001-.002 (there was some runout apparently) and at exactly 42.5mph and 85mph it hits soem harmonic and goes brummbrummmmbrummmm. Gets old quick.
Unless I turn left, if I turn left the swingaxle pushes in on the right side cover and gives it just enough clearance to shut up LOL That's how I knew what it was!! It might have worked better with a NEW set of gears but I think.... old gears are set in their ways and don't like to change backlash.

[youngnstudly]

[gears]

The old wisdom of zero backlash FOR DRAG CARS ONLY was in part to compensate for dramatic forward pinion movement, which put the R&P backlash into probably the .020+" range at launch . Eliminate that forward pinion movement (which in small part is due to main case flex), and more sane clearances can be used.

Let's see the bluing pattern from a zero (or very low) backlash R&P .. without at least chamfering every tooth edge, it'll be pathetic.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[mark tucker]

the pattern @ .008 was ok but looked to need less lash,at 4 it looks like 6 would be perfect,but it isant loaded anyway neer what it will be.and I do have a thrust bearing on the pinion.soIm gonna leave it here as I will move atleast .002 under load and with heet/expansion of case & gears. it has about 20 inch pounds turning torque on pinion when it'a all cold and pree loaded .004 thou when it gets warm(heat gun&heater blowing on it.) it's free. warm the gears it's fine too. I did heat a case to see how much it grows to get the mesurements for how much preeload I wanted on pinion thrust bearing. seems to of came out what I wanted it to.

[nsracing]

If you are going to use the same R/P in the original case that has seen some running, you CAN go tighter specs.

But if you graft a R/P set from another case and mount to a different case, I can tell you it will not mesh properly to run those tight tolerances that BERG says. You can set it up loose, then lap the 'high-side' down, then move up the tolerance, then lap some more until all the high-side has come down to lap a final finish to run the tighter specs.

For street use, the factory specs are pretty much what I use. Pay attention to the pre-load specs on the pinion bearings, otherwise all the final drive adjustments will be shit.

It is a LOT of work to lap R/P to mesh really good. Harder if you cannibalize a set from a case and mount to a different case.

Hope this helps.

[mark tucker]

I swaped it from another case, this case had a klinkenbug gear but it was boogered up from a dead pinion bearing,so in go's the gleason gear out of the other trans.I compared the cases and only about .002 diferance in pinion case seat depth . so I accounted for that and the pattern looked good so i knew I was in the right depth . I gess if I wanted to spend another few months I could if installed the pinion & a 3rd gear in the other case and laped it in....(I probably would of deburred the pinion too like I thought I did..effing brain dead, deburred the boogered up kilinkenbug pinion, ) it should be fine...I hope as Ive never done ony of these befor and havent a clue as to how hard or soft the gears are compsred to the ritchmond,zoom,motive, eaton and other performance gears Im used to setting up along with being a lot bigger than these vw's. I set my dana 60 to .006 on the street,no issues at all and quiet not a squeek.witch is unusual for a 5:38 gear in a usa made diff.( had lotsa experance with the vette 79 wine gears.what a headache, I cant even begin to think of howmany of those we did) those were nicknamed wining little pig bastard.( vette center section is called a pig....well it looks like a pig's head.)