Flipping a rear diff for reverse rotation

[carnuck]

I'm thinking of doing this because I found a small diesel drivetrain, but it turns counter clockwise and it can't be reversed (that would make the timing belt un-serviceable) The front would need to be reversed, but that's easier since it's a chunk that can be popped apart to be messed with.

I know about plugging the breather and putting the lines and another breather hole on "top" as well as rotating the backing plates. I can't think of any other problems with this setup (I did it years ago in a '66 Chevy Nova to lift the rear and got 2 speeds reverse and 1 forward for my efforts!)

[eaglefreek]

Wouldn't you need to change to reverse rotation gears? They would be running on the wrong side of the gear if you reverse the rotation. What about lubing the pinion bearing?

[TheWraith]

The drivetrain carnuck is considering operates in the the opposite direction of what one could consider 'standard', rotation is opposite of what is in his Eagle now.  By flipping a rear axle his goal is to use it in the 'reverse' direction as it is designed to operate thus matching this new diesel powertrain.

Yes, pinion bearing lubrication would be a major problem.  This has been done on other types of rear axles but this issue had to be addressed.  Skip it and the axle won't last long.  I believe to resolve it in other applications new oil passages had to be drilled since the original passages were located on 'top' after flipping.  You might start researching this on another web site that is known for having a lot of pirates and 4x4 vehicles.  If you haven't been there, and if you post questions, the atmosphere there is the opposite of the Eagle Nest forum.  Here everyone is friendly and there are no dumb questions.  Over there most everyone is...not so friendly.

Another consideration is that your ring & pinion will be operating on the otherside of their teeth, what is considered the coast side, which is the weakest side.  If you didn't push it hard you could get away with it.  But since the factory rear axle is based on the Dana35, a notorously weak axle due to a poor ring-to-pinion ratio and small contact patch, I'd be concerned with strength and longevity.

The brake backing plates could be flipped from side-2-side, so your parking brake cables should be fine.  You'll have to move your brake lines.  Not a major task but one to list on the to-do list.

You'll want to scrutinize your driveshaft angles.  Someone on here may know for sure, but pinions are seldom perfectly centered.  They are intentionally offset to allow for a few degrees of driveshaft angle so as to allow the u-joints to run in sync.

If you can resolve the pinion bearing lubrication issue you could pull it off.  Just have to make sure the squeeze is worth the juice.

One more option I'd like to mention is using a front axle and turning it around to use in the rear.  It comes with its own challanges such as the pinion is off-set far to one side.  You could retube the pumpkin but it isn't cheap to pay someone else to do it.  You could do it yourself if you have the equipment.  You'd have to decide if you want to solidly lock the steering knuckels in place somehow, build it for rear steer (dangerous on the highway), or remove the knuckels during the retube process and find an axle bearing that will fit the larger front axle tube.  I'd go for the latter if I had to choose.  Or you cold not retube it, use it as is, and get a tc with a passenger side offset.  Problem there is that your front axle wouldn't line up then...unless you flippped it too.

If you are dedicated to such a build, my hats off to you as it would be a major undertaking.

What kind of application did this diesel drivetrain come from?  You can't get a rear axle with it?

[carnuck]

It's actually FWD and I'm thinking of mounting the motor sideways. I won't have low range, but the transaxle should operate like a center diff. Limited slip is available. I already looked into reversing the transaxle's carrier, but it's not doable. The oiling problem would be covered by overfilling the system, but that's not a big issue other than possible axle seal leaks. I'm looking into a different trans, but the only other RWD alternate is an SR4 AFAIK. The motor is miniscule and only 45 HP. It's an attempt at major fuel economy using European ideas.

[TheWraith]

What you describe has been done in rock climbing competition buggies.  The only mass produced automotive engine I'm aware of that rotates in the 'opposite' direction was made by Honda.  Sorry I don't know which engine it was but I'm sure it could be found easy enough.

Yes, in that configuration the tranny does operate as the tranny & TC together (center diff).  It works well in the buggies but they are purpose built allowing the frame & axle arrangement to be built around the power train.  I could see it fitting in an Eagle if you can resolve the axle rotation issue.  Would be pretty neat.

I would still expect running the axle full of gear oil to still cause problems.  The oiling passages in the axle the way it is built now are engineered to allow the proper flow of oil to the bearings.  Simply running it full might not allow the oil to flow around the bearing properly.  Not trying to be a negative nancy but I'd expect trouble in the form of bearing failure.  If you try it I'd love to know how it stands to the test of time and miles, but strongly suggest you have a plan B just in case.  I would hate to see you go all the effort and expense of building it only to be stopped by a failed axle setup.  I'm sure with some research you could figure out how others have flipped axles successfully.  Might be an added expense in the form of some machine work, but if it makes it a successful project then it will be worth it.

In the end using a different diesel engine would put you way ahead in development, build time, and expense.  There are a lot to choose from if you look outside the US.  Even a few here in the US to choose from like from a VW or the first generation Jeep Liberty.