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Discussion Starter #1
So I fucked up the air line on the new 8.4 diff. Between the way EGCS routed the air line, my ignorance of clearance between the bearing cap and the front wall of the diamond and my dumbass thinking that the third just needed a little help seating in the housing I've managed to completely crush the air line running from the seal housing to the bulkhead fitting.

I've ordered a new one from poly performance, but I'm wondering what it takes to actually replace that seal housing.

Looking at it, I think all I need to do is pull the bearing caps, slide out the old, slide in the new and torque down the bearing caps again. Do I have that right? or is there some pre-load someplace that I have to pay attention to? I shouldn't have to fuck with the shims should I?

Maybe Brian will chime in?



 

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That is an odd place to route that line. Even in a stock Tacoma it would have a high risk of fuckup.

If your differential was set up correctly it shouldn't really need new shims. Mark the location. Check your backlash. If it is the same old to new you should be good to go. Make sure the preload doesn't change much either.

Did you do the vacuum line?
 

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Discussion Starter #3
I cut the vacuum line away to see how fucked it was. there were some zip ties holding the line in place as well.

What do you mean by mark the location? are you talking about making sure the same caps go on the same side they came off of? or ??

Also, what preload am I checking and how do I check it?

I'm assuming the "check the back lash" is simply setting up a dial gauge against the ring gear teeth and rocking it back/forth while holding the pinion stationary?

Os is this a case of "if you're too dumb to understand the directions, you shouldn't be touching it"?
 

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Ive done it on a v6 third and it didn't take long, but i don't remember much because that was 07
 

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NorCal Chapter Pres
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Remove the carrier and keep the shims together with the bearing races. Do not mix them up.

Remove the old seal by wiggling out of place. You may need a screwdriver but do not allow the screwdriver to touch the sealing surface AT ALL

Apply lots of lube to the new seal and wiggle into place

Reinstall. If the bearing preload was setup correctly from ECGS, you will only e able to get the shims 1/4 to halfway down using hand pressure. The rest of the way will have to be tapped in with a plastic mallet or a chisel rounded off so it does not damage the shims

Rebolt together. If you have a dial indicator, recheck backlash every other tooth. If not, and you trust ECGS, don't worry, just run it

Also, when tightening the nut that goes through the third with the oring, do not over tighten ;)
 

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Discussion Starter #7
NorcalPR.... Thanks for the detailed info.

As usual, Brian provides excellent info as long as you have a basic understanding of how something works. That always drives me into research mode to understand what he's talking about :lmao:.

Diff's are one of the few things I haven't gotten into yet. I guess it's time to learn and stop asking for 2nd grader level instructions. I really haven't run across a "diff 101" post. Most say to visit/read Zuk's site, which again, has outstanding information as long as you understand the basics. Part of what intimidates me is not understanding how things like pre-load/backlash/etc effects driving on the road/trail. The other part is how those things are adjusted and how making a change to one thing effects other things.

If anybody has links to that kind of "intro to differentials" please let me know. Once I have some kind of grip on "how things work", understanding what/how to check and adjust becomes simple.
 

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Discussion Starter #9
I should have known to search thru Bella Vista's docs before asking for links. :rolleyes:

Thanks.

I've been doing a bit of searching/reading. The more I read, the less intimidating it seems. Right now I'm trying to figure out how to hold the diff securely. I like Zuk's work bench setup, but mine is small and multi use. I'm trying to decide on how to make a jig that's secure, but removable.
 

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NorCal Chapter Pres
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It's quite easy. Just remember that you are dealing in thousanths of an inch, and a little change can change the pattern. Just the wrong torque on a bolt, or a tiny bit of runout, can change the pattern slightly.

As for holding the third, I just took two pieces of square tube, and welded a tab to it that extends about 1.5" off the side of the square tube. I then drilled a hole for a 8MM bolt.

I bolt the third onto the tabs, lift the whole thing onto the workbench, and clamp into place.

As far as your question

Part of what intimidates me is not understanding how things like pre-load/backlash/etc effects driving on the road/trail.
Preload determines two things. More preload will reduce gear deflection, which is a good thing, because when gears deflect, the pattern changes to a less favorable one, which causes the gears to break. Too much preload though, will make the bearings fail.

For the pinion, on new bearings, you don't want to exceed 20 in lbs. For used, I wouldn't exceed 10 inlb. For used bearings you just have to determine how used they are. The idea behind preload is that when the bearings are at the end of their usable lifespan, the bearings are still under a bit of tension so that things don't wobble around.

For the carrier, on a 8.4, IMHO you cannot get enough preload on the bearings. To get a decent ammount of preload, you have to tap the shims in. One shim higher and you can't shove it in. Same thing for these bearings, no more than 20in lb for new.

You can measure pinion preload easily, but not carrier bearing preload easily. To measure CBPL, you have to install the carrier with no gear. Then somehow spin the carrier with a wrench attached, to read the figure. With a 8.4, just get it as tight as you can, you won't get about 20in lb...

For a 8", Zuk already calculated it. For 10 in lb, you need roughly 100 ft lb torque on the sidewheels. For 17in lb, you would ahve to torque around 150 ft lb on the sidewheels.

As far as depth goes, I always have this argument with other gear installers. Zuk sets them up favoring the deep side of the ring gear, as do I. Why? The pinion teeth are stronger. So by going deeper on the ring, means you will be shallower on the pinion. Which ok, they're stronger anyways. Also, when the gears deflect from being under load, the pattern will work towards an even balance anyways.

The trick is to not go too deep that you take too much strength away from the pinion, and to also keep things quiet.

Too tight of a backlash means that when the gearset is running, oil cannot get between the teeth, resulting in more wear. I feel tighter backlash leads to a stronger setup, especially if the pattern is ballanced between coast and drive, and between the heel and toe, but favoring the heel. A loose backlash will generally make the difference between goast and drive greater.

It's a balance. Get the pattern balanced as close as you can, but not burning up the gears. I don't go tighter than .005"...

-Phill
 

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Discussion Starter #11
ok, now that I've got it mounted and got my hands on everything, it's starting to make sense.

My backlash is about .007-.006 measuring every 3 teeth. It either measured one or the other, but it wasn't consistent with each measurement, meaning i could check 4 places and they would all be .007, then I'd get a .006 then back and forth, etc. It could just be my technique or user error, but I figured I was good since it was always within .001

I realized that I don't have a small enough in/lb torque wrench to measure preload, so I'm trying to track one of those down. Zuk linked some bike shops, and I found a small local shop that shows they have one "at the warehouse" so i'll check with them in the morning to see if "at the warehouse" means they order it online for me or if they actually have one on hand.

Reading Zuk's site, it seems that he is measuring CBPL by differentiating pinion preload with and without the carrier (If i understood it right):
http://www.gearinstalls.com/jon8point4.htm (just shy of half way down the page)

Since I don't have that luxury, I was just going to check the preload at the pinion as is. I'm figuring the overall goal is to take it apart, put it back together and get the preload (measured at the pinion) and backlash to be the same as before I fucked with it.
 

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Damned air lines... Sounds like if you'd gone with an auto locker that you'd be golden. I love my ARB in the Taco, and have never had a single problem with it. But lots of guys do have trouble with them. The lockers themselves are pretty bomb proof, but that air engagement setup is not perfect. I like the concept of the new (I wanna say its the ZIP) air locker that defaults to the lock position instead of unlocked like ARB. Brian's ARB front locker wouldn't engage at AZRocks at all. Sucks to have an expensive locker like an ARB and not be able to get the damned thing to engage. That'd piss me off. I love my Detroits (but I don't street Zilla in the ice and snow either).
 

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Discussion Starter #13
Well, I got the carrier broke down, seal housing replaced. I was super careful removing and reinstalling the orings. I got it all put back together and the backlash/ preload numbers didn't change!

I didn't have fittings to bench test it, so I just hooked up the air line and cycled it a few times. It held air for 90 min before the compressors cycled. I know I still have a slight leak in my manifold and the compressors cycle like that with the locker turned off, so I'm calling this a success. If I hadn't torn my air setup apart 50 times already, I might have looked at it closer.

Thanks for the help, advice and instructions everybody!

I think Im going to keep collecting tools n stuff, then try installing some gears in a spare 3rd just to see if I can do it (and have a useable third).
 

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NorCal Chapter Pres
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Looks good.

Buy the inchlb wrench from amazon. Cheapest and easiest place to get it from.

How far were you able to get the shims in by hand?
 

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Discussion Starter #17
Just about like you said... I got it about 1/3 of the way by hand then a few light taps with a hammer and rounded chisel and I was golden.

Getting the shim/carrier out was a little tricky. I used a brass drift, but mine's pretty fat and cheap so it has a tendency to mushroom and chip. i had to keep stopping to grind the drift down a little so I could grab the shim and not the bearing.

Like most things I've done to this rig so far... It seems intimidating, more so as I read threads but when I actually dive in, it's really not that bad at all. Of course (again like most things I've learned/done on this thing) I need to get some trail time to see if I actually got it right. I'm figuring on pulling this third a few times over the season to re-check the pattern and wear.
 

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As gears wear in the pattern will become more difficult to read. The driven side of the gear will be the worst (coast side in front applications).

About the only way to get a pattern on a used set of gears is with massive amounts of loading. I use a prybar and jamb it against the ring gear. It somtimes works. I recently set up a set of gears for my 83 and could only read the coast side.
 

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NorCal Chapter Pres
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^ to load the gears for a pattern you can put plenty o load on gears by putting drag on the flange with a rag, hole spinning the carrier with a wrench.
 
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