Caterpillar No 12 Grader Tandem Project

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langlc06

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Hello all,
I am working on an old No 12 s/n 9K3722. It appears that the tandem pivot bearings failed quite nicely and got chewed up in the chains. We were able to get everything apart and find a donor machine to supply the new bearings, sprockets, and chains.

We are looking for guidance though on how to correctly size the shim pack on the bearing that goes from the tandem to the rear differential? The donor machine and the machine we are fixing both had a different number of shims in the pack and we were not sure how to make sure we hat the right offset.

Is this something that you have to assemble the tandem housing on the bearing and measure how far out the axle sticks? If so what is the spec?

Another question, does anyone have a good way of pressing the hubs back on the spindles in the tandem? What is the press spec? I have seen some posts mention possibly 40 tons, but I wanted to make sure.

We are going too look at the other tandem on the right side of the machine as well, because it was starting to tip up into the machine. Any thoughts on what we should inspect while we are looking?

Any thoughts or comments appreciated!

Thank you!

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Mon, Jun 29, 2020 10:19 AM

Deas Plant.

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Hi, langlc06.
I don't have the specs you need but I suspect that somebody will turn up with them soon.

I just want to make sure that you know that these machines DO NOT have a differential. That tandem drive is a LOCKED UP system to ensure that all four wheels drive ALL the time. For this reason, it is advised to keep all 4 tires on the drive as equal as possible at all times, preferably matched from new, in order to reduce strain on the drive axles and the chains in the tandem cases.

Just my 0.02.

You have a wonderful day. Best wishes. Deas Plant.

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Mon, Jun 29, 2020 12:14 PM

langlc06

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Reply to Deas Plant.:

Hi, langlc06.
I don't have the specs you need but I suspect that somebody will turn up with them soon.

I just want to make sure that you know that these machines DO NOT have a differential. That tandem drive is a LOCKED UP system to ensure that all four wheels drive ALL the time. For this reason, it is advised to keep all 4 tires on the drive as equal as possible at all times, preferably matched from new, in order to reduce strain on the drive axles and the chains in the tandem cases.

Just my 0.02.

Yep understood. I should have used the term final drive i think. It is a pain cribbing up the entire rear end of the grader to get the chains off of one side.

Anyone have any thoughts on the shim specs?

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Sat, Jul 4, 2020 11:16 PM

Deas Plant.

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Reply to langlc06:

Yep understood. I should have used the term final drive i think. It is a pain cribbing up the entire rear end of the grader to get the chains off of one side.

Anyone have any thoughts on the shim specs?

Hi, langlc06.
If you can lift the front wheels around 18" off the ground with the blade, you can raise either side of the tandems.

To do this, set the blade square across the machine and centered under the frame. Then raise the front end about 18"off the ground. When you have this done, 'raise' the blade on the side AWAY from the tandem that you want to lift. The balance of the machine will cause the tandem on the side away from the one on which you 'raised' the blade to come off the ground.

Then crib away to your heart's content.

If the controls are so worn that you can't lift the front by using both controls together, try using them alternately, one at a time.

You may find some useful information in this 'ar-tickle'. (Then again, you may not. LOL.)

http://www.acmoc.org/bb/showthread.php?20409-Cat-12-Graders-Pre-G-series

Just my 0.02.

You have a wonderful day. Best wishes. Deas Plant.

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Sun, Jul 5, 2020 12:21 AM

D4Jim

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Location: NW Kansas

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Reply to Deas Plant.:

Hi, langlc06.
If you can lift the front wheels around 18" off the ground with the blade, you can raise either side of the tandems.

To do this, set the blade square across the machine and centered under the frame. Then raise the front end about 18"off the ground. When you have this done, 'raise' the blade on the side AWAY from the tandem that you want to lift. The balance of the machine will cause the tandem on the side away from the one on which you 'raised' the blade to come off the ground.

Then crib away to your heart's content.

If the controls are so worn that you can't lift the front by using both controls together, try using them alternately, one at a time.

You may find some useful information in this 'ar-tickle'. (Then again, you may not. LOL.)

http://www.acmoc.org/bb/showthread.php?20409-Cat-12-Graders-Pre-G-series

Just my 0.02.

Are you removing the tandem axle or how much are you removing and replacing? I am not the expert but I have never seen a service manual for the tandem drive, only a short supplemental manual for the transmission.

Cats Forever

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Sun, Jul 5, 2020 2:19 AM

edb

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Reply to D4Jim:

Are you removing the tandem axle or how much are you removing and replacing? I am not the expert but I have never seen a service manual for the tandem drive, only a short supplemental manual for the transmission.

Hi Team,
there are a few different era SRB's that have been issued over the years covering this subject over some 9 pages.
SRB for early Graders such as the 9K would be Form No, 7401. For an 8T Grader, Form No 30124, which would be suitable also.
I was hoping some else may have chipped in here as a Computer Crash lost all my Cat and other stuff saved or scanned over 16 or so years for me, so it looks like I will have to redo them. Several back up files I have from over the years seem to not be able to be read by new computer.

Basically the SRB's say to turn the main axle bearing retainer around so the step is facing outwards, without the shims fitted, tighten the bolts down evenly with equal clearance gap all around until all clearance is removed from the bearings, Measure the shim gap and install shims plus 0.010"--this will allow 0.010" end play in the axle bearings.

There are no specs given for a axle to sprocket protrusion dimension or tonnage to re-fit the sprocket--later 12E book gives 25 to 30 tons.

Hope this helps.
Cheers,
Eddie B.

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Sun, Jul 5, 2020 8:10 AM

langlc06

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Reply to D4Jim:

Are you removing the tandem axle or how much are you removing and replacing? I am not the expert but I have never seen a service manual for the tandem drive, only a short supplemental manual for the transmission.

Hello,
I am only tearing down to the tandem bearing behind the sprocket. The axle, bearings, and seals, appear to be good on the final drive assembly. I wasn't going to tear down further unless the axle ended up being out of true.

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Tue, Jul 7, 2020 12:08 PM

D4Jim

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Reply to langlc06:

Hello,
I am only tearing down to the tandem bearing behind the sprocket. The axle, bearings, and seals, appear to be good on the final drive assembly. I wasn't going to tear down further unless the axle ended up being out of true.

[quote="langlc06"]Hello,
I am only tearing down to the tandem bearing behind the sprocket. The axle, bearings, and seals, appear to be good on the final drive assembly. I wasn't going to tear down further unless the axle ended up being out of true.[/quote]

Just wondering how the tandem repair was progressing. Hopefully maybe it is complete.

Cats Forever

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Fri, Jul 17, 2020 10:19 AM

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