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TLR3100 gearbox bearing insert shims?

TLR3100 gearbox bearing insert shims?


Old 06-12-2018, 10:53 PM
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Default TLR3100 gearbox bearing insert shims?

Hi I have bought the above for my scbe.I am not sure where the shims go.Well I know where they are ment to go but how many on either side.I looked at the scte 2.0 manual but it doesn't show the shims.Thanks for any help.
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Old 06-13-2018, 03:58 PM
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Originally Posted by martin34 View Post
Hi I have bought the above for my scbe.I am not sure where the shims go.Well I know where they are ment to go but how many on either side.I looked at the scte 2.0 manual but it doesn't show the shims.Thanks for any help.
The idea behind shimming and differential's ring and pinion gears is simple: get the gear lash minimal with no binding. This is similar to when you set the gear lash between the spur gear and the motor pinion. Obviously though with the spur/motor pinion gear lash, your moving the motor in its mount to set this gear lash.

These shims are found in most of the 4WD drive trains that employ front and rear differentials that are driven from a center driveline (center diff and dog bones).

This may seem like a lot of steps (work), but it is not. I just spaced the steps out to hopefully make it easy to understand. Once you perform these steps, it becomes obvious of what you are trying to accomplish and easier the second time you do it.

First, you need to figure out the TOTAL amount of shims needed. Then, from that total, decide how many of those go on the left side and the remaining shims on the right side.

A common mistake that most make is NOT accurately determining the TOTAL amount shims needed. To accurately do this, the pinion needs to be removed. With the pinion in place, you can get a false sense of certainty when the ring gear possibly hits the pinion.

Here are the steps:
1.) Remove the pinion gear from the gearbox
2.) Place the 2 aluminum bearing inserts onto the differential bearings with NO shims
3.) Place the differential into the gearbox, properly lining up the aluminum bearing inserts (as if you were properly assembling the gear box for final assembly)
4.) Hold the gearbox in one hand and grab the differential outdrives with the other. Force the differential side to side to determine if there is any play with NO shims installed

In step 4, you're simply trying to see if the differential needs any shims. In most cases it will. This will be obvious by being able to move the differential side to side as it moves within the aluminum bearing inserts

5.) Remove the differential from the gear box, taking note of how much play that you felt in step 4
6.) Remove one of the aluminum bearing inserts (either one - doesn't matter at this point)
7.) Insert 1 shim, then re-install the aluminum bearing insert
8.) Re-insert the differential back into the gearbox
9.) Repeat step 4, looking to see how much play is present AFTER adding 1 shim
10.) Repeat steps 4 through 9 until there is NO play at all

At this point, you have added as many shims were needed to remove any side to side play of the differential within the gearbox, with all of the shims on one side of the diff. If you continued to add more shims, you would start to put additional pressure on the bearings, as you forced the differential into the gearbox. This additional pressure will cause unwanted drag in the drivetrain.

Along these same lines, having exactly the amount of shims to remove ALL play allows no room for any possible expansion of the differential when it heats up. To play on the safe side, the next step is to allow room for possible expansion to avoid any drag due to the differential expanding.

11.) Remove the differential and aluminum bearing inserts
12.) Count the number of shims that you added
13.) If you added 5, you will only use 4 TOTAL

14.) Re-install the pinion gear back into the gear box

At this point, if you ended up with 4 TOTAL shims, all that is needed to do now is to determine how many of those shims go on the left and how many on the right. The goal is to place the appropriate amount of shims on each side to set the gear lash properly: not too tight where the gears are grinding against each other, but not too loose to risk damaging the gears.

15.) Place ALL of the shims on one side of the diff (pick a side, doesn't matter)
16.) Install the aluminum bearing inserts
17.) Insert the differential back into the gearbox
18.) Check the gear lash

If gear lash is too tight or too loose, take 1 of the shims and move it to the other side. In other words, if you determined that you needed 4 TOTAL shims and all 4 shims are on one side, you will now have 3 shims on that side and 1 shim on the other side

19.) Repeat steps 16 - 18 until you get an acceptable gear lash between the ring gear of the differential and the pinion.

Recheck the gear lash once you bolt the gearbox back together. In fact, I'll wait to add the grease to the ring and pinion until AFTER I bolted the gearbox back together, as the grease sometimes and make the "feel" of the gear lash more of a challenge. So, I'll bolt the gear box together and check the gear lash. If good, I open gear box back up, grease the ring and pinion, then close the gear box back up. If the gear lash changes when you bolt the gear box back together, repeat steps 16 - 18, combined with bolting the gearbox together to get your optimal gear lash, through proper shimming.

Properly shimmed diffs do 2 things:
1.) Make for an efficient drive train
2.) Prevent stripping expensive ring and pinion gears
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