Axle swap...

[DazSpaz]

Got a second gen 1500 5.9 auto 4x4 .
Stock rear axle was a 3.9. 9.25 12 bolt .
Can I put a 3.55 9.25 12 bolt on without doing anything extra? Does the rear axle gear ratio have to match the stock ratio to make 4x4 work without conflict between front and rear axles?
Thanks.
Dazspaz

 

[crash68]

Front and rear axle ratios must match on 4X4 and/or AWD vehicles. Tire sizes must be the same also.

 

[DazSpaz]

Thank you for the quick reply.
Back to the scrap yard I guess...

 

[Gr8bawana]

Got a second gen 1500 5.9 auto 4x4 .
Stock rear axle was a 3.9. 9.25 12 bolt .
Can I put a 3.55 9.25 12 bolt on without doing anything extra? Does the rear axle gear ratio have to match the stock ratio to make 4x4 work without conflict between front and rear axles?
Thanks.
Dazspaz

Unless you want to run undersize tires on the rear to account for the difference.

 

[WilliamS]

Differentials determine rotations per drive shaft turn. All 4 wheels must turn at the same rate or cover the same distance per axle turn. So you can technically run different ratios but you would need the tire size to accommodate the rotation differences. So if the front axle is 10% numerically shorter the the tire needs to cover 10% less rotations, or is it more, brain broken 3am and baby won’t let me sleep. This is not the right way so on a 4x4 if You run the same size tires you need the same size gears.

If not the same gears would cause binding in the center differential Because the front and rear driveshaft will be trying to turn at different speeds in which would break a lot of things if you were in 4 x 4 with different gears or different size tires now this won’t affect anything if you never use 4 Wheel Drive you can use whatever gears you want.


In short change both front and rear to same gears, run same diameter tires.

 

[WilliamS]

Unless you want to run undersize tires on the rear to account for the difference.

This actually a proper solution to your scenario, understanding it is a different story but this is actually a correct answer to your question.

 

[DazSpaz]

Thanks all for the info.

next question:
is there a chart or page on this forum that lists all compatible, no mods necessary, rear ends for the 2nd gen ram 1500s?
What other vehicles can I include in my hunt for a 3.92, 9.25 12 bolt rear end?
I think for now I am going to put the donor 3.55 on there and disable the 4x4 so that we can actually use the truck for the time being and while I hunt for a 3.92 donor.

Much thanks again.
DazSpaz

 

[WilliamS]

The 2nd gen you can swap both gears without changing axles

 

[Demon-HeMi]

I've cleaned up the BS, If you have problems with each other take it to PMs, Keep it friendly folks or this thread will be closed...

 

[dapepper9]

OP, the 3.92 axles weren't overly common to have. Not saying rare, just not overly common. You may be better off simple having the factory rebuilt or swapping both axles to the more available 3.55

 

[Demon-HeMi]

I'll throw this in for just for fun because i did the same thing back when i was just out of HS, i had a 4x4 s10 blazer lifted on 35s, i blew the rear axel and my truck had 3.55 in front and rear,I went to the junkyard and pulled me an axel that was supposed to be the same gear, found out it was like a 3.2x or something like that, as long as you're off road you can use 4x4 and not hurt anything, but i did try it once on the street, and man that was one hell of a ride when you have 2 sets of swampers pulling at different speeds, lucklly i didnt break anything...


but moral of the story is you can run the different ratios front and rear, just dont put it in 4x4 while on pavement, mine lasted years until i sold the truck wheeling it every weekend in the mud

 

[DazSpaz]

Anyone have any experience setting backlash without a dial indicator?
I got fed up with no one knowing what the shrapnel was I found in the pumpkin and pulled the differential out. The bits were pieces of the clutch pack inner shim plates and the retainer clips. Im getting new plates and clips today as well as replacing carrier bearings.
I did NOT find any play in the pinion bearing so have left that alone. No seal leak either.

So all I have messed with is the differntial itself so backlash and carrier bearing pre load is all I have to set now. (i wish I knew before hand I could do the clutch packs with the differential in place, although you can't change the carrier bearings without removal so i guess I would be pulling it anyways).

So back to my original question now...how possible is it to set back lash with our a dial indicator? Perhaps using marking grease? There must be someone out there wh has redneck solved this or knows a way to do it with out the dial indicator.
Thanks ahain. Again....
DazSpaz

 

[G-Ride990]

Anyone have any experience setting backlash without a dial indicator?
I got fed up with no one knowing what the shrapnel was I found in the pumpkin and pulled the differential out. The bits were pieces of the clutch pack inner shim plates and the retainer clips. Im getting new plates and clips today as well as replacing carrier bearings.
I did NOT find any play in the pinion bearing so have left that alone. No seal leak either.

So all I have messed with is the differntial itself so backlash and carrier bearing pre load is all I have to set now. (i wish I knew before hand I could do the clutch packs with the differential in place, although you can't change the carrier bearings without removal so i guess I would be pulling it anyways).

So back to my original question now...how possible is it to set back lash with our a dial indicator? Perhaps using marking grease? There must be someone out there wh has redneck solved this or knows a way to do it with out the dial indicator.
Thanks ahain. Again....
DazSpaz

Marking with grease will just show you the gear mesh pattern. Why don't you want to use a drop/dial indicator? You can get one from HF or amazon for like $10 if you want to go cheap with it. I have calibrated those cheap ones before and they really aren't bad.

I suppose you could use a protractor and do the math for rotation based on the pitch/pressure angle of the gears. For gear inspection purposes I have done this in the past. But it would be way easier to use an indicator.

 

[DazSpaz]

Marking with grease will just show you the gear mesh pattern. Why don't you want to use a drop/dial indicator? You can get one from HF or amazon for like $10 if you want to go cheap with it. I have calibrated those cheap ones before and they really aren't bad.

I suppose you could use a protractor and do the math for rotation based on the pitch/pressure angle of the gears. For gear inspection purposes I have done this in the past. But it would be way easier to use an indicator.

Thanks for the reply. Both those options you listed are wait for shipping options. And my parts store will have one but even with a discount it will be pricey. In short I'm impatient. Truck has been on blocks for a month because everyone says how horrible it is to mess with a diff. I was searching for a donor rear end to swap in but I'm my area a 3.92 is hard to find for some reason.

What's the potential damage done if the backlash is not exact? Backlash is really just the side to side setting of the differential itself using the bearing race adjusters inside the inner axle correct?
Cheers

 

[DazSpaz]

I'll throw this in for just for fun because i did the same thing back when i was just out of HS, i had a 4x4 s10 blazer lifted on 35s, i blew the rear axel and my truck had 3.55 in front and rear,I went to the junkyard and pulled me an axel that was supposed to be the same gear, found out it was like a 3.2x or something like that, as long as you're off road you can use 4x4 and not hurt anything, but i did try it once on the street, and man that was one hell of a ride when you have 2 sets of swampers pulling at different speeds, lucklly i didnt break anything...


but moral of the story is you can run the different ratios front and rear, just dont put it in 4x4 while on pavement, mine lasted years until i sold the truck wheeling it every weekend in the mud

Thanks man. I appreciate the real-life experience. I wondered about that actually if it would matter when you're in snow or slop as tires would not be able to grip at the same rate and could spin freely anyways which would not result in binding.
Thanks

 

[G-Ride990]

Loose backlash will feel like drive train slop but exaggerated. Basically a clunk when breaking and an equal clunk when accelerating. (assuming that that drive line has a chance to freewheel)

Too tight of back lash and you won't really notice any issues while driving. You will however wear the bearings out much faster than you normally would.

Yeah you adjust the backlash with the threaded adjusters. There is a special procedure to set everything right though. A quick search on google, "how to adjust chrysler 9.25 differential" will get you there.

 

[DazSpaz]

G-ride .
Thanks for that.
From what you're saying then it's notninstant carnage as soon as you roll away after buttoning everything up?

Which bearings will die prematurely?
Carriers or pinion?

Could I not set the backlash roughly and then run a test drive and then adjust if necessary?

As for the Google search I have seen a couple guys do it with no mention of setting backlash, one guy reinstall with marking grease and no dial gauge, and then numerous with the gauge.

 

[Gr8bawana]

Just seems strange asking for opinions on how to do it the wrong way.

 

[DazSpaz]

Just seems strange asking for opinions on how to do it the wrong way.

You ever think some people may live in an area where all the **** you can walk down the street for is not available?
Do everyone a favour and don't comment unless it's useful info man.

 

[DazSpaz]

You're doing an awesome job of making an othrwise awesome group look like **** man. Well done. Keep it up. It would be nice to see you get the boot or at least a periodic suspension from posting for a while as other groups do when someone is posting purely to be a *********.