Question on flipping Rockwells... and a Spicer prob!

[Scuffy]

Hey gents! I'm getting pretty excited now as I finally have the 2.5 ton Rocks, Spicer 3053a and PTO unit from a Deuce as well as several other goodies. Now it's time to start putting everything together. I've got a few questions which I can't seem to get an answer for on a few of the 4x4/Jeep forums I'm a member on so I figure I might as well as the gurus!

First off. With the Rockwells I know that many want a different side drop so they rotate the the top portion of the differential around. Most of the holes line up, a couple need to be drilled and tapped. I understand that part. BUT... (yes the infamous "BUT" ) I've seen several builds of different vehicles where they are running Rocks with full hydro steering- the ram, being balanced or unbalanced, along witht the tie rod on the FRONT of the axle. I'm having trouble wrapping my mind around how this is done. Is the axle simply spun and mounted backwards IE the passenger tire is now on the driver's side and vice versa or have they swapped the outer ends around. More simply- if the top portion can be rotated would it also work to run the axle backward instead? I have a fairly technical mind but axles in general just confuse the hell out of me!!

I plan on running full hydro so this is a bit of important info!

Also! I've been searching the net up and down and have found many instances of folks running a 53 series Detroit with a Spicer 3053. Even a couple guys that have a Gama Goat 3-53 paired with the Spicer. Both of mine have the SAE#3 pattern on them- the flywheel housing on the engine and the bell on the Spicer. But I need a bell housing that will let me mount them together. The shallow bell on the trans is obviously not deep enough to allow for a clutch plate and all the accoutrements. In fact the input shaft sticks out a good 6" or 8". Does anyone happen to know what bell housing I might need or what to pull one off of?

And... I think that's it for now. I'm exhausted from thinking about this stuff and searching so hopefully you guys can shed some light on my most recent set of questions! lol

THANKS!!!

 

[mudguppy]

... First off. With the Rockwells I know that many want a different side drop so they rotate the the top portion of the differential around. Most of the holes line up, a couple need to be drilled and tapped. I understand that part. BUT... (yes the infamous "BUT" ) I've seen several builds of different vehicles where they are running Rocks with full hydro steering- the ram, being balanced or unbalanced, along witht the tie rod on the FRONT of the axle. I'm having trouble wrapping my mind around how this is done. Is the axle simply spun and mounted backwards IE the passenger tire is now on the driver's side and vice versa or have they swapped the outer ends around. ...

yes, when mounting a steer axle under a Ford or Dodge (w/ driver's side transfer output) the diff chunk is removed and rotated 180°, and the entire axle housing is rotated around as well. this will leave the front diff input only slightly off-center towards the driver's side.

if you wanted, the knuckles can be swapped from one side to the other to move the tie-rod fore or aft of the axle input, wherever desired. however - when you rotate the axle around, you are taking the castor angle that is built into the axle housing and now reversing it. though, this isn't usually a concern for offroad rigs.

... More simply- if the top portion can be rotated would it also work to run the axle backward instead? ...

techinically, yes - the input rotations will still make for correct forward/reverse directional outputs. however (again), running the diff backwards [in effect] can lead to other problems.

the first set of reduction gears is similar to a standard ring and pinion - designed for either standard or reverse rotation operation. running the diff backwards would apply primary operating torque (ie. forward) onto the opposite sides of the ring and pinion gears - something they were not designed for. theoretically, this could lead to increased heat, fatigue, and eventual failure. most likely, you'll experience premature pinion bearing wear.

typically when offroad rigs add pinion brakes - doing so put a tremendous amount of operating torque on the reverse side [effectively] of the diff when the diff is run in the standard arrangement. because of this, the pinion bearings (and seals) get worn out very rapidly. even if you weren't going to run a pinion brake, the example is applicable and i would imagine that the resulting symptoms would be similar as well.

while running the diff in this "backward" arrangement would probably alleviate the premature wear from the pinion brake scenario (since not the braking force is applied in the "standard" direction), you'd probably still experience rapid pinion wear and associated symptoms by running input power through the "backside" of the diff.

 

[russ81]

Mudguppy is 100% correct. If you look at the cut angles of the ring gear the "front" side is is cut square while the "back" side is cut at an more of an angle. The angle cut on the rear acts as a gusset to support and strenghten the running side. Running the gear in reverse, because of the increased angle, adds a tremendous amount of "thrust." This thrust is absorbed by the pinion bearing. During normal operation where your only running in reverse for short distances, and not under large loads, the wear is unnoticed.
If you run in reverse for long distances, or under large loads, you can litterally blow apart your ring and pinion set up apart because of this angular thrust.

 

[Scuffy]

Hmmm... yes I can definitely see where running it in a backwards mounted situation might prove to be a bad idea now!! And I have to say thanks guys- sometimes I just need to be able to see things to understand them, otherwise they just don't make sense. And it's a bit hard to get one of those axles to tag along to work with me!

Any ideas on the engine to transmission pairing??

 

[russ81]

I'm putting together a Cummins 5.9 24v with a NV4500

 

[JasonS]

Mudguppy is 100% correct. If you look at the cut angles of the ring gear the "front" side is is cut square while the "back" side is cut at an more of an angle. The angle cut on the rear acts as a gusset to support and strenghten the running side. Running the gear in reverse, because of the increased angle, adds a tremendous amount of "thrust." This thrust is absorbed by the pinion bearing. During normal operation where your only running in reverse for short distances, and not under large loads, the wear is unnoticed.
If you run in reverse for long distances, or under large loads, you can litterally blow apart your ring and pinion set up apart because of this angular thrust.

I believe that the technical term for the primary reduction is spiral bevel. However, I don't see how operating in reverse would result in a thrust load while forward would not. The pinion is supported by tapered roller bearings and would seem to me to support thrust loads just fine.

 

[mudguppy]

... I don't see how operating in reverse would result in a thrust load while forward would not. ...

there are thrust loads in forward - it's designed for this, but not for the opposite.

ring and pinion gears (which have spiral bevel cut teeth) have an angle that exerts thrust loads slightly like a worm gear. the greater the ratio (numerically higher), the greater the angle of the bevel on the teeth and the higher the thrust load. this style of gear cut allows the pinion gear to be set off-axis of the corresponding ring gear. only a straight cut gear tooth does not result in axial thrust, but then the pinion and ring gear must always be perfectly aligned which takes up space. plus, a straigh cut tooth is a very noisy and rough running set up, especially in an ring/pinion application.