Big plans for the heavy chevy

[Wahugg]

Why not jack one side of the truck up, put the Tcase in 4x4, transmission in neutral, and mark the wheels that are off the ground in the same spot with chalk. Then rotate them (assuming you don't have a rear locker) and if the chalk marks stay in the same spot then shouldn't it mean the gear ratios are the same?

-Wahugg

[DirtyBacon04]

Thats not a bad idea. i'll have to give it a shot.

[ErikSS]

I like the conecpt but I think the drivetrain has too many variables for that to be accurate enough to find small differences. The cluthes in the limited slip axle and the clutches in the Tcase could easilyl scew the distances.

[DirtyBacon04]

Well i tried it. One full rotation forward. Spun by the front tire and the rear lagged by about 30 degrees after a full rotation.
Leads me to believe i dun did got fcked by the salvage yard guy. Son of a bitch... Not happy.

[Shdwdrgn]

Ack that's bad! Did they admit to a mix-up, or did you check the ratio yourself? What's the actual ratio you got, and is it the front or rear? Sounds to me like they should be paying for the next replacement.

[EDIT] oops, mis-read your original comment. OK so for what it's worth, here's what I've seen with mine... Starting with the original 3.42 gears in 4HI, I would frequently get a lot of resistance when backing out of my driveway to the right at a moderate turn, to the point that sometimes it felt like the whole drivetrain locked up. With the new 4.10s, I have not felt this in reverse (yet), however I did notice when I was testing 4HI after swapping the front diff that coming up to an intersection and making a left turn at anything more than a very light throttle would make the driver's side front tire try to skip.

[DirtyBacon04]

I didnt check the ratio. The tag said 4.10, but clearly that doesnt seem to be the case. They haven't admitted to it because I just came to this conclusion and haven't told them yet. I'll try and contact them tomorrow.

[Shdwdrgn]

Sorry, see my edit above...

You know, we used to check rear ratios by lifting one tire off the ground and rotating it while counting rotations on the drive shaft. I wonder if that trick works on the front the same way?

[ErikSS]

I don't believe a 30 degree difference in tire rotation is accurate. That's an example of the driveline variables. Since I know one of your axles is 4.10, the biggest variable would be if you went all the way to 3.42. That is a 16.6% (wouldn't cause 30 degrees) change. With one limited slip axle and one open, the only way to measure distance (then calculate gear ratio) would be on the ground with matching tires and tire pressures.

I used this sites gear ratio calculator with your 33" tires.

[ErikSS]

EDIT:
I went over my numbers again. 30 degrees is 1/12 of a rotation. About 16.7% Um, maybe I'm wrong! That could be if you have a 3.42 against a 4:10!

[dvanbramer88]

Check the front and rear independently again. Jack the whole rear up, in neutral. Spin the tires and count the rotations compared to the rotations of the drive shaft/pinion.

Same for front.

But if Erik's math is right, the second time, I'd believe it. And if you only used the 4x4 on sand and loose ground, it could be possible that you would only feel a little "weirdness" but totally possible that you wouldn't notice rolling down the trail.

Now I'm really curious of how this turns out

[Wahugg]

I don't think the TC would slip enough to make a huge difference. As Roadie has pointed out before, our TC clutches act like a locker in 4 high and 4 low with. Our vehicles will hoop a wheel due to bind up before the TC slips. If Auto 4x4 then yeah, the TC will slip a LOT!

Also does Bacon have a LSD differential? I'm not 100% sure on how they function, but I don't think it would alter how much the tire would be rotating in relationship to the front wheel if one wheel of the axle was on the ground.

Now I would take drive-line play into effect here. Slop in the front diff, front u joint, T-Case, rear u joints, and rear diff will all exaggerate the total turn difference to some degree.

I would personally do what I stated above (only jacking the truck up on one side), rotate the rear wheel clockwise until the front wheel is moving with it (eliminating slop) then mark the 6 o'clock position of the wheels WITHOUT turning the wheel counterclockwise, and then continue to turn it clockwise a turn, SLOWLY letting it come to a stop. This way any inertia of any rotating parts in the driveline will be minimal, thus not reintroducing any more slop that we had just taken out of the equation which could affect the overall amount the tires are off.

For example, my ATV has so much slop in the drivetrain, I can turn the front wheel 1/16th of a turn before it affects the rear wheels. By keeping all the rotations in the same direction and by slowly stopping the turning, it eliminates the 1/16 driveline slop form the equation if I were to do this procedure.

Hopefully I don't sound too crazy over here.

Good luck on figuring out what happened!

-Wahugg

[Trail X]

He doesn't have an LSD nor a locker, so it should operate properly. You just don't know if the 30 degrees was due to driveline slop - gear slop in the diffs.

I'd probably try to spin it multiple times in a row, and see if the 30 degrees continues to add up over each rotation.

Otherwise the easiest way I can picture to do it is to lift all 4 tires (or I guess 2 on one side would work), and put it in 1st while in 4 lo. Should spin the tires fairly slowly. See if the fronts are spinning faster or slower than the rear. That should give you an idea of which diff is wrong (the faster one is the non-4.10).

But yeah, based on what you've said so far, especially the binding in the parking lot, you've got one of the diffs geared wrong.

As long as you haven't driven it on the pavement much, the rest of your driveline might be ok. But why did you try it while going 15 mph?? I would have tried it going 0, and then eased very slightly off the brakes and allow it to creep into a stop. The gears slowing you down like that had to absorb a lot of energy.

[ErikSS]

The slower one will be the 4.10. You go slower per RPM with higher gearing.

[DirtyBacon04]

Thats what he said, just the opposite wording.

[Wahugg]

I also just remembered a bulletproof way on how to tell what gear ratio your rear diff is. Remove the rear cover and the ratio should be printed on the ring gear. That way you can at least eliminate that diff as being to right or wrong ratio.

-Wahugg

[v7guy]

Generally it is on the ring gear, you can also do what a couple other guys have suggested and turn the driveshaft and count the revolutions at the wheel. I find marking each with some chalk helps. I hate to say it, but it really does sound like the wrong gears are in there.

[mikekey]

I certainly hope LKQ didn't burn you on that rear-end. Now you've got me nervous about ordering one. Hey man, if it does turn out to be a lower gear and is still infact an 8.6 let me buy it off of you (depending on what you want ). We're going 4.56 anyways so I need to pick one up to re-gear it. And we can finally meet up.

[jonbo2002]

give me the VIN of the replacement axle and I can get the actual ratio to see if they inventoried it wrong. I know I have ran the VIN on mutiple axles in my company and they have been wrong. I have sent emails to them to get them corrected. Thats why I have said before " anyone on here ordering an axle from LKQ please message me first and I will run the VIN for you to make sure it is the correct ratio."

[DirtyBacon04]

Sorry Mike. Seems to me that the rear axle is the one that's correct.
I'll try and get the VIN for you, if i can remember. I'll have it up on the lift later today at the shop. I'm also convinced it's the wrong ratio.
Bacon ANGRY!!!!

Who knows, maybe this is karma's way of telling me to take pictures and complete the write up... Or maybe i've been watching too much "my name is earl"...

[jonbo2002]

the VIN should be on the invoice you got when you paid for it, if you didn't get one ask the yard you got it from and they should have the VIN on record. If its from LKQ and you have a stock number that would work too.