IHADAV8.com - Turbo Buick Tech, and Nonsense
Tech Area => General Buick Tech => Topic started by: Bob-Lob-Law on April 13 2014, 05:03:08 PM
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Well, got the new diff and all associated parts. I have gotten all the seals and bearing installed and just finished the differential install. I used the instructions for Posi Conversion on gnttype.org to help me with the install. I installed all the shim and the driver's side was pretty tight and I had to tap in the shim which was stated in the instructions.
Now that I have everything in, I'm ready to do the marking compound test, but I have one question first: How tight is the differential supposed to be? It's a bit hard to turn. One way is pretty easy, but the other way is pretty tight and I have to use both hands to get it turned. Is this normal?
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Shouldn't be that tight. Usually turns pretty freely.
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Yeah, thought so. I'm going to take it apart tomorrow after work. Thanks for the help.
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Maybe you should do a tooth contact pattern before you rip it apart again, might help narrow the fault in case you don't see anything obvious.
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I am no expert but I always check the backlash first since that is easy :)
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Agreed, but from what he's saying I would bet there is zero backlash.
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we think differently :)
It is easy to grab the ring gear and see if there is any free play....if there is not, then there is not sense in checking tooth contact...pull a shim out and get the backlash in spec, then do a tooth contact.
No backlash makes it hard to rotate.
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Gentlemen: Thanks for all the input. This is definitely a new thing for me as I have never done this and I was hoping to never have to.
You are correct Steve, there is absolutely no backlash at all. This was the same way when I pulled it apart, hard to turn and absolutely no backlash. Looks like I'll be looking up the spec for backlash. A fine part from gbodyparts.
Thanks for the help. :rock:
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Believe it is 6-10 thousandths...
Gary's probably the best advice. It's too tight, so a tooth contact pattern should tell you which way the ring gear needs to move which will entail pulling a shim(s) on one side or the other. There should be a good tutorial online how to know what to do....
If this is an used rear end-hopefully you can avoid worrying about the pinion depth and just concentrate on moving the ring gear side to side....
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I thought doing a tooth-contact test was mandatory when rebuilding a diff?
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Believe it is 6-10 thousandths...
Gary's probably the best advice. It's too tight, so a tooth contact pattern should tell you which way the ring gear needs to move which will entail pulling a shim(s) on one side or the other. There should be a good tutorial online how to know what to do....
If this is an used rear end-hopefully you can avoid worrying about the pinion depth and just concentrate on moving the ring gear side to side....
I was going to say that it sounds like no backlash but you guys covered that. If it is a drag car you use less back lash I believe compared to a street driver.
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I thought doing a tooth-contact test was mandatory when rebuilding a diff?
generally after the backlash is in range. In this case, I figured it was easy to check the backlash before smearing the compound on the teeth...if the backlash is not right, it is too early to worry about pattern.
It gets more complicated if you have removed/replaced the pinion
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I was thinking he did a new ring and pinion. That's what I get for thinking. :rolleyes;
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Either way he has to figure out where to go now!
Steve
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Got a link to the instructions Bob? How much was the install kit and where'd you get it?
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I got the install kit at justdifferenti als.com. I'm not doing the pinion gear as it looked like it was in perfect shape (imagine that). I ended up having to take the differential out before I could check the pattern. The differential was way too tight to do that. Now, I'm just going back to basics. I found a Youtube video on how to determine the proper amount of shim. I'm going to try that out first then I'll go with the checking out the pattern.
Here is the vid link: https://www.youtube.com/watch?v=UpOMSt2iEA0 (https://www.youtube.com/watch?v=UpOMSt2iEA0)
Thank you for all your help guys.
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Question. If you DON'T remove the pinion gear...and you install the caps the same as they come out and install the shims the same way they came out...should the gears not mesh the same? All you've done is bolted the ring gear to the new posi unit...and reinstalled the caps and shims the same as they came out.
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I erased my earlier thoughts because I didn't see the YouTube drunken video. After seeing the PBR presentation, I had to rethink any input. Scoobum, you're partially right and I think that is where most problems start. All the dimensions of the replacement carrier including bearings, ring gear, and housing have to be exact. Throw in the new ring gear to old pinion, it seems to be a noise issue waiting to happen. Personally, I hate to see a new ring gear matched to a pinion that has alot of miles on it. Keep in mind there is two sides of the gear set set: drive and coast. I don't know about you, but when I decel from 120, I want all to be good and a soccer mom wants all to be quiet. One of the issues he seems to minimize in the video is the pinion depth. At the end of the video he mentions he might have to redo his work, which may include pinon depth adjustment, or maybe not!! But, the pinion depth adjustments are shims under the pinion bearing. So that means, pull the driveshaft again, pull the axles again, pull the carrier again, press the pinion bearing off, install shims from your computations, install a new crush sleeve for preload and proceed. You Tube most times is good entertainment. You really have to sift thru the BS.
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Pyro6, I should have mentioned that I'm keeping the same ring gear too. So, the ring gear and pinion should be matched up.
Scoobum, I thought that everything would match up as well, but putting the left shim in was incredibly tight. I'm thinking that there must be a couple of thousands difference, probably because all the bearings and the differential are new. Not sure. With there being some nasty storms here right now, I'm not able to work on it. I'll have to wait until tomorrow.
I'm thinking of just using the same shim on the right side and replacing the left side shim with one a few thousands thinner as the backlash was very little.
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I was wondering if you could get away with it...guess not.
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I have several times...