TC Gear Adjustments

[er82]

I was wondering if anyone could give me some pointers with the transfer case for a drag racing.

Here is what I have:
95+ center bearing housing.
1991 iron housing.
F*F brace.
New bearings.

The output shaft (driven gear) measures just about 1 nm of torque (1.43mm preload, and .22 mount spacer), so I think thats good.

But the drive gear measure only 0.25 nm torque. It supposed to be like 1.7nm minimum. I'm using 1.58mm preload spacer and 1.52mm mount spacer. Also, the backlash is just about .004" and attached is pic of contact patch.

Which preload spacer should I use? And should I change any mount spacer to adjust the contact patch?

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[twicks69]

Well, you can do a solder test in place of your bearing preload shim with trying 0.062" solder first, then going to 3/32" solder if you aren't crushing the 0.062". I am guessing you have next to nothing for bearing preload. I typically have around 0.004"-0.005" preload on the side cover bearing.

Here's a list of the shims -
MN168245 - 0.0386"
MN168246 - 0.0421"
MN168247 - 0.0457"
MN168248 - 0.0492"
MD723600 - 0.0528"
MD723601 - 0.0539"
MD723602 - 0.0551"
MD723603 - 0.0563"
MD723604 - 0.0575"
MD723605 - 0.0587"
MD723606 - 0.0598"
MD723607 - 0.0610"
MD723608 - 0.0622" - 1.58mm
MD723609 - 0.0634"
MD726170 - 0.0646"
MD726171 - 0.0657"
MD756760 - 0.0669"
MD756761 - 0.0681"
MD756762 - 0.0693"
MD756763 - 0.0705"
MD756764 - 0.0717"

 

[OGDSM1989]

You used way to much Marking compound first of all, for your transfer case you need only a slight amount on 2 maybe 3 teeth if your try to use that method ....but using solder is a much easier way to check back lash.
The compund in your case is way to messy to make any assumption on bearing pre load or shims needed

 

[twicks69]

I use machinist dye in red and blue and I put turning torque on the tcase with an output shaft and keep resistance on it when doing my revolutions in each direction to watch my contact patterns. I also put a relatively high thickness side cover shim in it to confirm my backlash numbers first, then I change the backlash shim until I see it getting tighter, and do typically 3-6 adjustments if necessary, and I do side cover preload testing up to around the 0.007" range, and also play around with my pinion bearing preload shim until I like how its turning by hand.

Alot of the tcase is setting it by feel and contact pattern. I don't use rear diff marking dye (yellow paint stuff you have) because it is so damn messy. I just use Dykem layout fluid (red and blue).

 

[er82]

Thanks for the input guys!

I cleaned up the yellow paint and turned the gears more. So the contact patch looks more clear now. Seems pretty centered.

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I used the 3/32 solder wire to measure the space and it's about .0630"

So I calculate as follows:
.0630" (actual space) - .0598" (mount spacer) + .0622" (current preload spacer) + .004" (desired preload) = .0694"

Closest preload spacer MD756762 - 0.0693"

Does that seem right?
Also the manual has MD724339 as part number for drive bevel gear preload of .0693". Did they change?

 

[er82]

Or is that .0630" space supposed to be taken up by the mount spacer? like MD723609 - .0634" and then use .0669" preload spacer to get .0043" preload?