Gear Stack Clearance Setup

[rayhawk]

I am building a type I trans for my 72 super street car with about 160 hp. I will be using stock gearing from a 74 box (3.78 1st), except I will be using my 4.12 R/P and my AH trans case. I am getting coarse tooth bus gears as well. (1.26 and 0.89). I am looking for some details on setting up the gear stacks. My info is from the Berg book, but I would like to hear some opinions on what is necessary or worthwhile at my power level. I will go to the track occasionally on street tires and am looking to run high 13's.

This is what I am planning on doing so far. Remove first gear shim, adjust clearance by machining drive hub to decrease endplay to 0.001". Drill 1/8" diameter oiling holes in gear contact area on drive hub and chamfer holes. Hand pack needle bearings for first & second gear.

I don't quite understand how you set the clearance for second/third gear on the pinion shaft. The Bentley book talks about different circlip thicknesses, to adjust 3rd, but it is not too specific about 2nd? How would you decrease play on second? Especially if you move the hub over to decrease play at first? What did I miss?

Should I use a solid spacer between third and fourth? Should I consider the thrust bearing mod for the end of the pinion shaft I have read about using my stock gear carrier?

For the mainshaft, is handpacked needle bearings needed? As for clearance here, I was going to set at 0.004" for 3rd and 4th. I was also going to drill and chamfer this drive hub to improve oiling.

What else did I miss? I plan on getting a chromoly pinion nut and using the SSC case with a 2 ring factory side cover. Also getting a super diff with 10 tooth spiders.

[dangerous]

The reduction of clearance on second gear can be achieved by removing material from third gear.

But this assumes third gear is fixed with the correct circlip or a solid spacer.

The solid spacer will wear out if it is not held down tightly with a threaded pinion,
but if you drill through the hard end of the circlip style pinion shaft you can tap it M10x1.5, and make a cap that clamps 4th gear,
and everything under it, down.

I personally never run end clearances as tight as .001" any more.
Oil holes help, but most times the faces will burn.
Gear oil needs more room than that to work properly.
Remember that 1st gear and 4th gear have the highest relative speeds against their shafts in use.

Third and 4th will need the hub modified to use 091 circlips because the 002 ones allow the hub to float and change the end clearances.
Wih the original 002 circlips, the thrust loads will allow 4th gear to become too tight.

I like to set end clearances to minimum .006", and 4th gets the maximum of .010".

VW 1st gears need help,
so hand pack if you want and use tighter end clearance.(I never use less than .004")

I might add here that with aftermarket strength gears I use more clearance on 1st gear.
I have used as much as .020"(due to tolerance stack-up) on 4th with no adverse effect,
but the maximum of .010 should be heaps.

I just use early full length needles with a cage and keep end float at minimum while using the oil holes.

Also worth consideration is the relative speed of the gears on their shafts.

1/ Until the car moves the mainshaft spins within 3rd and 4th at engine rpm(7500 launch in my case).
Thus lots of clearance needed.

2/ with the car in 4th gear the pinion is spinniong within the large 1st gear, some times faster than engine speed depending on what 1st ratio, and what 4th(overdrive) ratio.
Thus, lots of clearance needed.

3/ Think about the speed that third gear spins at relative to the case when engine is full steam in 4th gear.
If pinion is going, say, 7000....the 3rd gear idler will be faster by the 3rd ratio....not much prob since the input shaft is at engine speed, but what if you are coasting down from speed...
The speed of the third gear idler would be high enough to throw off most of its oil.

[Pablo]

You need to throw that little booklet away. Use a minimum of .004" on 1st & 2nd, and a minimum of .006" on 3rd & 4th. Like Dave said, the oiling holes are nice, but not a substitute for adequate clearance.

Hand packed needles are for drag-only transmissions. They will produce too much heat in a street transmission.

[Bruce2]

..... decrease endplay to 0.001".

DO NOT, DO NOT, DO NOT, do this. The thrust end of 1st gear will gall badly to the 1st gear thrust washer. If you do it to 2nd, it will gall badly to the 1-2 hub. Stick to the tolerances in your Bentley. Much easier to build that way too. I know of one well known VW trans builder that even says you can go looser, up to .012". Gaps let oil in. No gap, no oil. Drill the 3 oil holes, it is a good idea with no downside other than the labour to do it.

Should I use a solid spacer between third and fourth? Should I consider the thrust bearing mod for the end of the pinion shaft I have read about using my stock gear carrier?

For your hp level, use the stock spring. You are so far from needing the thrust bearing mod too. Keep it simple.

[rayhawk]

So removing the first gear shim is recommended right? This shim on the trans I took apart recently was in real bad shape. So if I remove this shim, then I would have to machine the drive hub to move closer to first gear. The only way to then set the clearance on second is to remove material from third, and then use a solid spacer between third and fourth to hold third in place and maintain that clearance. Do I have this right? I then leave out the third gear circlip? Or will the different thickness third gear circlip sizes be enough to compensate for the shim removal?

Dangerous, you say you use early full length needles with a cage, are the bearings I have from the 74 good enough for 2,3,4 gears in my case?

So are the handpacked first gear needles overkill/bad idea for a street trans?

This is really clearing things up for me, thanks for the help.

[dangerous]

When you remove the shim, you need to machine the first gear to get some clearance back.

I very rarely remove the shim any more.

In theory the thicker circlip should be used after third is fitted,
but the sprung spacer should keep third gear seated there
except under hard decelleration.

You may like to use two conventional circlips to get the thickness you need,
but I am unsure how they would handle the spring against them for any huge milage.
No worse than the wafer thin first gear shim.

For my own tranny I have used two, but dragracing is short term, and I like to try different things.

I use early bearings with metal cages on all but third, since they wont fit over the 002 hub spline on the main shaft.
Weddle, ERCO, and any bearing shop,
sell a steel gaged bearing that has a split cage in two halves.

But the reality is the stock bearing will be fine in that location with your power.

I have never been happy using hand packed needles
because they locked the gear up like a sprag when rotated both ways
and the rollers leaned over.
As Paul stated above, take his advice.

The late bearings are fine for your use,
but perhaps a steel caged LONG roller race for first gear.
It will need to be well lubed,
and well supported.
I also radius the oil slots in the face of the first gear
with a 1/2" sanding roll to help the oil wedge.

[Bruce2]

So removing the first gear shim is recommended right?

No, leave it in and build the whole gearbox just like stock. 160hp is NOTHING! A stock trans can handle that hp.

If the 1st gear shim is beat up, put a new one in. Or better still, install a 76 or later 1-2 shift hub that has the groove on the OD near where the shim went. This hub is thicker by the amount of the shim.

[rayhawk]

Well I do plan on abusing this trans at the track from time to time (on radials) so I would like the trans to be up to the task within reason. My car is also pretty heavy-about 1950 lbs w/out driver.

You say to rebuild like stock, I still should run a super diff, right?-I can check it and correct run out if necessary, so that should not be an issue.

Also I am going to buy bus cv's and the drive flanges, etc to adapt.

[Henryhoehandle]

You could also put in a 091 first (idler) gear and gain a little more strength.

[Bruce2]

Well I do plan on abusing this trans at the track from time to time (on radials) ....

Radial tires afford very little traction, so there's even less reason to do all the silly mods in the Berg book.
Keep it simple, stock plus a few other upgrades.

Use a superdiff
Chromoly pinion nut like you stated above
coarse tooth Bus 002 type gears
If you can get the steel cage needle bearings for the idlers, use them.
Bus CV joints

I think you should also use this:

http://www2.cip1.com/ProductDetails.asp ... D5058%2D10

[Spoonboy84]

For anyone looking to limit pinion movement because of high horsepower and hard launches we developed a drop in tapered roller bearing for the end of the pinion. Same idea as the Timken bearing mod I've heard mentioned before, but no machining required.

https://www.facebook.com/RKMachineShop/ ... 1632090281

[gkeeton]

For anyone looking to limit pinion movement because of high horsepower and hard launches we developed a drop in tapered roller bearing for the end of the pinion. Same idea as the Timken bearing mod I've heard mentioned before, but no machining required.

https://www.facebook.com/RKMachineShop/ ... 1632090281

Your bearing mod looks very interesting. Could you please start a new topic with detailed photos describing the modification, and installation?