Rockwell T221 Speedo gear tooth total?

[CKfan]

Picked up my Rockwell T221 N5 and SM465 that I had rebuilt and dropped it in today. Had the shop go through everything. Instead of tanking the cases we hand cleaned everything with degreasing agents to save the original paint and markings. Came out looking the way I had hoped.

They said the transfer case was in pretty good shape so things went fine...... except the speedo gear was/is missing from the case. Really!

I am trying to find another but have no idea which one to look for. 11 tooth, 17, who knows? Not my strong suit and the shop said it would take some research but it is related to the gear ratio??? So, here I am. : ) Picture #1 shows what I am looking for but tooth total is unknown

On the plus side of this, I am glad they were honest and told me. When she gets back together and my speedo didn't work, I would have been tearing into everything from the dash down.

[jocko]

There are two gears - the drive gear (on the o/p shaft) and the driven gear (your 1st pic). Can you confirm which you are missing? - your statement from the shop was a little ambiguous. (I'm assuming you are missing the driven gear since that is the pic you grabbed off the internet, and because that is usually what is missing, not the drive gear - but highly recommend you take a peek inside the case and confirm your drive gear is still present, just to make sure).

Do you still have the housing/sleeve that captures the driven gear in the case?

The item in your hand is an aftermarket s/w speedo compensator (with a .944 ratio) - only necessary if the original tire diameter and/or r&p ratio had been altered from stock. It's not necessary if your truck has its original rear end ratio and you are using stock diameter tires. If your truck doesn't have either of those (now), it "might" help - or it might not - kinda depends on whether your tire/gear combo is the same as whatever the PO that put it on was trying to compensate for.

What is your tire diameter and what is your rear end gear ratio?

[CKfan]

I know it gets a little technical but my eyes just glazed over. : )

It is the driven gear that is missing.

Drive gear still in place (will try and count teeth somehow)

Housing/sleeve still intact

3.73 in the rear end.

P/O ran 7.00 - 15 LT tires

I will run 8.25 - 15 (most likely)

Thanks for your help

[CKfan]

Housing

[jocko]

Once you know drive gear tooth count, you can calculate what tooth count you need for the driven gear.

For 3.73's w/28.5" dia tire:
Driven Gear Teeth = Drive Gear Teeth x 2.6369

Edit: that should get you close to correct without the need for the compensator. Once you get everything installed, check speed indication vs GPS and then maybe that compensator will come in handy. You may need it if the 'closest available' tooth count driven gear wasn't real close to what you calculated.

For others' reference with different gears or tires, here is the formula:

Driven Gear Teeth = Drive Gear Teeth x Gear Ratio x Tire rev per Mile / 1001
(Tire rev per mile = 20,168 / Tire dia")

[CKfan]

Much appreciated. Will give it a go in the morning.

[CKfan]

Got it! Saw the part # on drive gear with flashlight 1898-P-848

4T (tooth), R,H., Helical, 1.876" O.D.

4 X 2.6369 = 10.5476 (11 tooth)

Called Torque King for driven gear part. They said it can only be one of three. 11, 12, or 13 tooth and they are out used stock and no-one re-pops them. Good luck finding one. Yikes! The hunt is on.

Just another day with this project. : )

[jocko]

Not sure if it will help, but you never know which of the 3 options may pop up for sale first. They are rare - but don’t forget your compensator - depending on what you need, the compensator could make the wrong one “right” enough. I also recall reading the actual gear can be pressed off the shaft - just in case you find pieces/parts.

[cbeerman]

It's GM part number 2396889 (SW 448663)

If you can't find one, I may have an extra.

[CKfan]

Thank you for the replies and information. I am searching the net and have a call into Meritor.

Thanks again.