Setting up gears in an 8-3/4

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fishy68

fishy68

Tyr Fryr's Inc.
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Ok I bought everything new to rebuild my 742 case 8-3/4 including a clutch kit for the sure grip, all new bearings, and a gear set. No problem rebuilding the sure grip but I've ran into a problem getting the right pattern on the gears. BTW: Their Motive Gears brand.

I don't have a pinion depth setting gauge but I figured since the bearing cap meets the housing in the center it should be close enough to lay a straight edge on and measure to the pinion for the initial run. First time I set it right to the number on the pinion (1.715) then installed the carrier and set backlash to .009-.010 then spun it a few times to make sure everything was seated in and rechecked the backlash and touched it up a little. Smeared on some checking paint and spun it a few times. It was way off. The pinion was way too far away so I pressed it back apart and added a .010 shim and put it all back together blah, blah, blah. Greased it up and checked it again. This time it looked alot better. In fact the drive pattern wasn't bad at all but the coast pattern was too close to the toe. Hmmm... So I pressed it all back apart again and shimmed it another .010 put it back together blah, blah, blah. Greased it and checked the pattern again. The coast side looks some better but still not deep enough. The Drive pattern is right on the money. If I shim it more the drive pattern will start going too far towards the toe I think.

I attached some pics. Didn't take any pics of the initial test cause it was way off. The first pic is the drive side with .087 shim an 2nd pic is coast side with same shim.

The 3rd pic is the drive side with .097 shim and 4th pic is coast side with .097

What do you 3rd member guru's think? Should I shim it more or is ok where it's at. If it was a 5 minute job I'd try more shim but since I have to press it all back apart and then back together again I thought I'd ask here first and see what you guys think. I don't want to hurt anything and preferably have no gear noise. The only thing that makes me hesitate on adding more shim is the fact the drive side looks real good.

Thanks, Tracy
 
Split the difference on the next shim if you can. The drive side usually doesn't change exactly proportionally with the coast because of the helical cut. How much backlash have you got with that pattern?
 
I've got the backlash set at .0095-.010 (varies a half a thousandths from one side to the other). The papers that came with the gears said .008-.012

I never thought about it not changing as much on the one side due to the way their cut. This is the first one I've done.

Would you have a guess as to how much shim to add? Another .010 or .015?

Thanks for the reply, Tracy
 
Wow, this is all Greek to me and I have to do this soon.
Carry on. :read2:
 
340 Dart said:
Wow, this is all Greek to me and I have to do this soon.
Carry on. :read2:
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from what little i know about this is the pinions have a depth set number on each one and the difference between the old and new numbers are what you add or subtract to your shim pack. it looks like your gettting real close to where you need to be.
 
bOb shingler said:
from what little i know about this is the pinions have a depth set number on each one and the difference between the old and new numbers are what you add or subtract to your shim pack. it looks like your gettting real close to where you need to be.
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Yeah I started with the number enscribed on the gear but it was waaayyy off. I'm allready about .022 past the original number. Tomorrow when I get back on it I'm gonna try .012 more and see where that puts it.
 
FWIW at this point, when I did my 741 with (with Motive Gears), since I replaced all of the bearings I took the old pinion bearing (large one) and hogged out the center just large enough so that it would slide onto the pinion without pressing. It sure made setup go easier. Then switched in the new one and rechecked when I got the shims figured out. And, I just started with the shim pack that was in it originally and went from there.
 
70Duster440 said:
FWIW at this point, when I did my 741 with (with Motive Gears), since I replaced all of the bearings I took the old pinion bearing (large one) and hogged out the center just large enough so that it would slide onto the pinion without pressing. It sure made setup go easier. Then switched in the new one and rechecked when I got the shims figured out. And, I just started with the shim pack that was in it originally and went from there.
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I thought about doing that but I thought there might be some difference in the bearing thickness since their not the same brand bearings that would throw it off. Maybe I was wrong in that thinking??? If I ever do one again I'll try that. I'm a newbie to this so am learning as I go. I believe you have a good point to start with the original shim from what I've seen on mine. If I would have started with it I would have had it apart two less times. Right now I'm .003 over the original shim and fairly close.

Thanks for the replies everybody. Tracy
 
That's why it's a learing exsperiance youll definetly know what to do the next time cudos for going at it most people wouldn't even try
 
fishy68 said:
I'll post back here tomorrow eve. what happens.

BTW: which case do you have?
Click to expand...
I actually have a couple to choose from a 489 and a 741. Both have 3.23's now and the stronger one is getting 4.56's.
Definately let me know how it goes. Anything I learn from you is more than I already knew.
 
340 Dart said:
I actually have a couple to choose from a 489 and a 741. Both have 3.23's now and the stronger one is getting 4.56's.
Definately let me know how it goes. Anything I learn from you is more than I already knew.
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Hijack alert:

Use the 489 with a solid spacer to replace the crush sleeve.

Back to the thread...
 
crackedback said:
Use the 489 with a solid spacer to replace the crush sleeve.

Back to the thread...
Click to expand...

That's exactly what I was going to say. I don't know alot about them yet but I do know if mine had the crush sleeve I would've gone through 3 already and one more to go. With the solid spacer you just add or subtract shims the same amount you changed behind the pinion.

I'll let you know tomorrow eve. how it came out.
 
Thanks for the link bustedknuckles. It has a bunch of good info. Just wish they were doing an 8-3/4 but at least the same principals apply. I see it says even backlash affects the pattern to a degree. I figured it might but wasn't sure how. I didn't read the whole article because it's so long and I don't have alot of time tonight so I saved it and will read it through when I get a chance.

I worked on it more today and got it alot closer but it seems when I shim far enough to get the coast side close to center the drive side moves off center quite a bit. I talked to a buddy that has set quite a few of them up and am going to take it by his place tomorrow and see what he thinks.

Here's some pics I did today that shows how shimming affects it.

The first 4 pics are with a .097 shim which is .005 thicker than the ones used in the previous pics I posted. As you can see the drive side looks spot on (pretty much the way it looked with a .0925 shim) but the coast side is still way towards the toe.

The next 4 pics are with a .107 shim (.010 thicker). You can see now the coast side is pretty close but the drive side has moved too far off center in my opinion but I'm no guru so that's why I'm taking it by my buds to see what he thinks.

I'll post back here tomorrow eve. what he thinks.

Thanks for all the replies. Tracy
 
Hey Fishy, before you make anymore shim changes I'd tighten up the backlash to .009" and that may help your coast. Your drive pattern looks really good in pictures 3 and 4.

Terry
 
demon seed said:
Hey Fishy, before you make anymore shim changes I'd tighten up the backlash to .009" and that may help your coast. Your drive pattern looks really good in pictures 3 and 4.

Terry
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Hey Terry thanks for the input. The backlash is set to .009 right now. So you think the drive pattern looks ok. The problem with me is I haven't done this before and don't know what's acceptable. I thought it was supposed to be more centered and no matter what shim I tried I couldn't get both sides centered up at the same time. That's why I was planning on taking it by my buddies tomorrow to see what he thinks. I'm going right by his house anyway.

Thanks, Tracy
 
fishy68 said:
I thought it was supposed to be more centered and no matter what shim I tried I couldn't get both sides centered up at the same time.
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You can't always get them both centered but that's okay. You get it as close as you can and go with it. I think you'll be fine.
 
Doesnt the factory call for 6-8 backlash. I like to run mine on the tighter side.
 
70Duster440 said:
You can't always get them both centered but that's okay. You get it as close as you can and go with it. I think you'll be fine.
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That's what my buddy Chris said today when he looked at it. He did say to tighten the backlash up to .008 so I'm going to do that and stick it in.
 
scamp 408 said:
Doesnt the factory call for 6-8 backlash. I like to run mine on the tighter side.
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According to my FSM it said .006-.010 The papers that came with the gears said .008-.012 so apparently Motive wants them to run looser. Chris told me today to tighten it up to the tight limit Motive recommended and go with it so that's what I'm going to do.

My bud Chris also seconded Duster440's idea to take the old bearings and ream out the inside just enough to slide on easily by hand and use them to get it close so you don't do like I did and have to spend time and energy pressing everything apart and back together every time. I think I pressed it apart and back together about 7 freakin times. I can't say it was enjoyable.

Thanks to everybody for their input and have a good weekend.
 
Great thread Fishy! the pictures make clear what the questions are talking about, and are the same ones I would be asking. Great advice, too guys! More, more!=P~
 
bugsy said:
Great thread Fishy! the pictures make clear what the questions are talking about, and are the same ones I would be asking. Great advice, too guys! More, more!=P~
Click to expand...

Thanks Bugsy. Hope it helps you and others. This is a subject alot of well experienced mechanics haven't ever dealt with because it's something not needed very often and it's pretty critical to get them right so it's good to know what's acceptable.
 
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