Dial test indicator for front differential backlash? (1 Viewer)

[highfructose]

It seems that a normal dial indicator works for the rear diff. However, instructions I’ve been researching say a dial TEST indicator is necessary for the front.

Would this dial TEST indicator be likely to work with the front differential on the 200 series for testing backlash?

https://a.co/d/18y4Ydf

note: I’ve already got the following dial indicator which worked on the rear diff…but the instructions for the front say you need the slightly different type of TEST indicator.

https://a.co/d/e30Vvvz

 

[bloc]

If you already have the magnetic base and arms I’d bet you can find one that attaches to that to save some money.

But yes the hinged-arm-type is needed so you can reach into the drain hole and measure the lash at a right-angle to the direction the indicator is pointed. The plunger of your existing tool can’t get into position on the tangent of the ring gear, which is needed to get an accurate reading.

IIRC Zuk shows pictures of this setup in some of his front diff builds, if you want to see what a pro does.

 

[hbar]

Might be the wrong audience for this caliber of reply, but the harbor freight magnetic base & dial indicator work perfectly well for setting up gears. I've done some, but also BFH Garage on Youtube has a whole series where he re-gears all the common axles found under jeeps. Same principles apply, same tooling works.

The first picture you posted looks "nicer" but it seems to have one less bend in the arm which could make getting the needle on the gear tooth challenging. It's hard enough to get the arms positioned right.

Although the HF set ends up being ~$30, whereas the 2nd one you posted is only $10 more and comes with a case and an array of tips which I could see being very handy.

 

[TeCKis300]

Might be the wrong audience for this caliber of reply, but the harbor freight magnetic base & dial indicator work perfectly well for setting up gears.

Nawh, I'm all for HF especially for seldom used specialty tools. Using the same dial indicator over a couple decades now that's built about 4 diffs. Works great.

 

[highfructose]

There was a dial TEST indicator on amazon for around $20 that easily fit on the base and arms of the dial indicator that I previously purchased.

I’m going to see whether the dongle is long enough to measure the backlash on the 200 series (tundra) front diff I plan to put a locker into.

Would anyone happen to be able to identify the metallic apparatus otramm is using under his diff in the attached photos that he’s magnetized his dial/dial test indicator base/arms to?

 

[bloc]

Sorta looks like a valve spring compressor.. but I can’t see enough of it to be sure.

Edit: yep, OTC 4572 large valve spring compressor.

 

[highfructose]

Thank you. I figured it was some kind of a clamp…I attempted to set my base and dial test indicator up using a pair of Vice grips clamped to a bolt back there. Looks like maybe it worked.

I need to figure out what otramm was levering against with his pry bar to turn the ring gear…then I’ll hopefully be able to ensure the dial test indicator is centered on the tooth face.

 

[highfructose]

The stock short “probe” on my inexpensive dial TEST indicator made for difficult measurements since the tool essentially blocked the small opening/drain plug in this clamshell (I think) style differential case…so you had to blindly attempt to place the tip of the probe on the face of the ring gear tooth.

In one of the videos I watched in this topic it was advised that they made longer probed dial test indicators.

Amazon has longer probes to attach to any dial test indicator for around $8. The thread on the probe isn’t standard though-there are multiple available. The following probe ended up threading appropriately into my gauge…and also allowed one to see into the differential to place the probe appropriately for measurement.

I may need to do some math though since the short probe appears to be 16.55mm and the long probe is 44.5mm.

 

[bloc]

You'll have to adjust your readings proportionally to the longer probe though, right?

 

[highfructose]

Yes. I’m not a big math guy…so I’ll have to figure out whether the proportions are equivalent…roughly speaking, 15mm vs 45mm of probe…and whether that means I should multiply the measurements by 3 while using the longer probe or some other number.

 

[bloc]

Yes. I’m not a big math guy…so I’ll have to figure out whether the proportions are equivalent…roughly speaking, 15mm vs 45mm of probe…and whether that means I should multiply the measurements by 3 while using the longer probe or some other number.

The important distance is from the pivot to the tip. Hypothetically if that number is now twice as long, you’ll need to double the number indicated on the dial. If it’s 1.5x, go 1.5 or 150%. Etc.

 

[highfructose]

The important distance is from the pivot to the tip. Hypothetically if that number is now twice as long, you’ll need to double the number indicated on the dial. If it’s 1.5x, go 1.5 or 150%. Etc.

Thank you. It sounds linear.

I wasn’t sure if I need to use the Pythagorean theorem or something.

 

[hbar]

The important distance is from the pivot to the tip. Hypothetically if that number is now twice as long, you’ll need to double the number indicated on the dial. If it’s 1.5x, go 1.5 or 150%. Etc.

How does the length of the tip matter? I could put a tip on that is literally a mile long and if I nudge it 1 thou at the far end the gauge would still only deflect 1 thou at the dial. What am I missing here?

 

[bloc]

How does the length of the tip matter? I could put a tip on that is literally a mile long and if I nudge it 1 thou at the far end the gauge would still only deflect 1 thou at the dial. What am I missing here?

The dial cannot tell how far the tip is actually moving like an in-line dial indicator does. This type measures the change in angle of the arm, and converts that to tip movement distance on the dial.

If you move the contact point further away from the pivot the arm doesn't change angle as much for a given tip movement. So you have to apply an adjustment factor to the readout.

 

[highfructose]

How does the length of the tip matter? I could put a tip on that is literally a mile long and if I nudge it 1 thou at the far end the gauge would still only deflect 1 thou at the dial. What am I missing here?

If you were to swing a 12’ piece of 2x4 1”…the pivoted end (as opposed to the swinging) would move imperceptibly.

However if you were to swing a 1” piece of wood 1”, then it might turn a full 45 degrees….the longer your measurement probe (in a swinging measurement), the less movement you will see at the dial.

Another way to think about it is if you stood at the North Pole during the rotation of the earth, you’re not really moving “around,” you’re just spinning in the same spot…whereas if you were to stand at the equator, you’re rotating through a wide arc of space as the earth turns.

Earth turns same speed…but based on your distance from the center line of it, YOU are moving a lot faster around in space as you get closer to the equator.

 

[highfructose]

For anyone trying to do this at home, the inexpensive dial test indicator listed above along with the extended probe above appears to have made for a relatively easy measuring of the front diff backlash.

• Otramm uses a large pry bar or chisel placed on the cross pin to wiggle the gears while disallowing movement of the input flange bolts of the diff…he appears to have leaned the bolts onto the work space to disallow that movement.
• I used a chisel with a medium vise grip on top of it to push the cross pin.
• Like Otramm, I placed some blocks of wood under the diff to place the pinion/input flange (if that’s the name for it) on the work surface so I could get a measurement on the face of the tooth on the diff
• I used a large vise grip clamped to a bolt as a magnetic “base” for the dial test indicator base (it needed to be relatively large to give a large flat plane for the magnetic base of the dial test indicator to be settled)
• I replaced the probe on the dial test indicator with a 45mm (I think) one (original was 15mm). This allowed me to see down the drain for the diff to place the probe on the tooth appropriately…you could do it without this, but this is my first time doing it and, at $9, the longer probe was worth a shot to make things easier/clearer
• I got 5.5 hashes “swing” on the dial test indicator (which won’t mathematically be the same as what I got with a 15mm probe).