Pinion gear and ring gear make up the gear ratio of the rear end or not?
Can I use a set of spider gears from 3.55 in a 3.92 I'm doing the clutch packs and carrier bearingsmon on?
Working on 9.25 12 bolt lsd 3.92 on a 98 dodge 1500 5.9 auto 4x4.
Donor axle is from a 9.25 12 bolt lsd 3.55 2nd gen 5.2 auto 4x4

Also
I have a great how to (found in this site) for setting backlash and carrier bearing preload but at the end of it, it says to perform the gear contact analysis procedure. Can anyone shoot me a copy of that?
Thanks ahead. I'll have more questions I'm sure. First time repairing / replacing any actual differential components.
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Ring and pinion determine gear ratio, spider gears have nothing to do with it. You can re-use them when you re-gear.

Contact analysis is simply putting marking compound on the gears, spinning them a bit, and seeing where the contact patch is. I believe that info is also in the service manual.

 

I know I can reuse them. I want to know if I can use the spiders and side gears from the 3.55 for my 3.92 as they are in better shape. If they don't affect gear ratio it shouldn't matter they came from a 3.55.
is this right?

Thanks

 

You are correct. You can use the side gears

 

Tech questions...

Finally have time to put the diff back today.
3.92 rear 1500 5.9 auto 4x4. New clutch packs, carrier bearings and races.

#1) what has everyone set, or aimed to set backlash to? I've read a span from 0.003 to 0.009...
I have it in my head .005 to .008 is acceptable..

#B) After its reassembled, is there anything I can do to verify its good before I install the axle back in the truck? Or after its back in the truck but before I've started up and test driven? Is there a way to know you're not gonna have carnage in the first drive?

#4) What an I looking for to know I'm safe to take it for a rip? Is it always obvious right away that you've made a mistake, or do some errors take time to present themselves?

#4b) anyone open the diff back up after a few trips to have a look? Any point to doing so?

98 ram 1500 magnum
5.9 gasser auto 4x4

Thanks ahead..again...

 

There should be specs in the service manual for backlash, and they are different for new, or used gears.

Once it is back together, use gear marking compound to test the pattern of the gear mesh. (there are pics of how it should look in the service manual as well, not to mention online.) If the pattern looks good, and everything is in spec, stuff it into the truck.

Once it is all back together under the truck, go for a ride. Have a listen. It should be quiet. If it makes ANY noises, something ain't quite right, and you need to recheck everything. If it is quiet, doesn't chatter around corners, and feels smooth. You are likely golden.

Couldn't hurt to have a peek after a couple hundred miles. Maybe use a clean pan, and if everything looks good, re-use the fluid.

If your front axle doesn't have 3.92 gears, do NOT use 4 wheel drive until you get those changed as well.

 

Thanks for the reply. Ya there are specs all over online, hence my question to the 2nd gen forum for the right specs. Service manual states .005 - .008 but does not specify for new or used, and when i pull the diff I did a backlash check and it was .003 so I wanted clarification.

I did the gear mesh pattern check and came out freakishly close to what the service manual says it should be. So thats a good thing. It did not look like that when I pulled the diff. Again I did a mesh pattern check before i pulled everything apart just to take pics and have a comparison, as well as fart around a little with **** that didnt matter so I was comfortable reading things when it did matter.

I have the axle back under the truck and everything seated but need to do final torques on u bolt nuts etc. Probably going to have the do or die test run tomorrow after work. As for the front end I know...I found that out the hard way after i bought a donor axle that was geared 3.55 and then thought about it a minute and asked the forums about matching front and rear gear ratios. Its next to impossible to find a 3.92 donor around where I am at which is what lead me to pulling this bastard and doing the clutch packs and carrier bearings. I wanted to avoid that based on how terrifying everyone I asked made doing the job (mainly backlash and carrier bearing preloads), but it went a lot easier than I thought it would after everyones horror stories. I guess I will find out in the end if it really was as easy as I found it compared to stories when I drive away and dont have any immediate carnage.

I most definitely will be opening it up after a few hundred kms just because my mind wont let me leave it alone even if it sounds wonderful while driving.Fluids will be tossed as I never reuse fluids. Ever.

I was a little worried when I got spiders and side gears in and I couldnt turn the sides by hand, but after talking to a lot of folks and then also putting the axles back in and being able to lock one and still spin the other I realized it was just due to brand new full thickness clutch packs. It rotates very smoothly so I am hoping the initial test run will be a celebration and not a disappointment.

Thanks again for the reply Man.

Cheers,
IB47

 

Is honestly not hard, it's just like everything else you need to take your time and triple check everything. Hardest part in my opinion is finding the right spacers. You should hear nosen (if anything is off) as soon as the truck starts to move.

 

Thanks for the reply.
Are you talking pinion gear spacers?

 

Shims or spacers whatever you call them. And yes for the pinion grea and for the carrier side to side. That is what always scared me until one day the rear went bad and I wasnt spending $1300.