Lets talk about a weird axle swap...

[kmas0n]

Ok, first... the swap I'm considering isn't actually into a TJ... So if that's your only thing. click away.

I have a little old flat fender... a 1942 Ford GPW. one of the weird Ford ones. and in the rear of that little jeep is a dana 27. That axle was fine for NDT tires, no lockers and stiff suspension, but that's not how I build mine. Mine has a 7.5R16 BFG mud terrains that get fantastic traction, and LockRight locker and a very very flexy 4 link/cantilever/trailing arm rear suspension. The result... I've broken two axle shafts in less than 500 miles of moderate off road.

The obvious upgrade would be a Narrow track Offset dana 44 for an early CJ... but these are getting rare. Hens teeth rare. So a full width dana 44 that I narrow down to the needed 48.25 WMS to WMS is likely going to be the only way forward.

Unless...

For the same amount of fabrication...

hear me out. An XJ hp dana 30, cut the knuckles off... weld on axle flanges, order custom lenght axle shafts. If you spin a driver drop axle to the rear, you would have a passenger drop (needed for my T18 T-case)... it would be high pinion, which would help driveline angles for my rear axle (I'm limit strapped at 13" of travel). The dana 30 has got a smaller housing than a 44 which would help with precious real estate, and ground clearance.. these little jeeps are small... bigger axles do not fit.

Here is what I think I know... The Dana 30 is basically a 44 except the ring gear (carrier) are only 7.5 instead of the 8.5 the 44's have. So they are pretty strong and can easily serve as a front axle on a 4500# Tj with 35's and 3 times the horsepower the flat fender has.

But do you think...

is a HP dana 30 running backwards strong enough to handle being in the rear of a 60 hp, 2400 lb jeep...

The downslide to a HP axle is that you are running on the coast side of the gears... which is fine for front end duty, but if it is on the rear of a vehicle... wouldn't you be running on the drive side of the gears again? Do you need normal cut gears instead of reverse cut gears?

So ... discuss. HP dana 30s are cheap and plentiful. Would it make since to modify one to be on the rear of a little jeep?

 

[hosejockey61]

I have a little old flat fender... a 1942 Ford GPW. one of the weird Ford ones.

Pictures!!!

But do you think...

is a HP dana 30 running backwards strong enough to handle being in the rear of a 60 hp, 2400 lb jeep...

The downslide to a HP axle is that you are running on the coast side of the gears... which is fine for front end duty, but if it is on the rear of a vehicle... wouldn't you be running on the drive side of the gears again? Do you need normal cut gears instead of reverse cut gears?

On a high pinion 30 in a front application, it runs on the drive side. If you were to modify it to run in the rear, it would run on the coast side of the gears.

 

[Wildman]

Pictures!!!

https://wranglertjforum.com/threads/trail_krawler-trail_willys.21015/page-48

 

[kmas0n]

Pictures!!!



On a high pinion 30 in a front application, it runs on the drive side. If you were to modify it to run in the rear, it would run on the coast side of the gear

Pictures!!!



On a high pinion 30 in a front application, it runs on the drive side. If you were to modify it to run in the rear, it would run on the coast side of the gears.

Is your run reverse cut gears, or maybe it's straight cut gears, does the move the load to the drive side... It is that not how it works?

 

[Wildman]

Is your run reverse cut gears, or maybe it's straight cut gears, does the move the load to the drive side... It is that not how it works?

Running a high pinion axle in the rear is on the weaker/coast side of the gear while running a low pinion in the rear you're on the stronger/drive side of the gear.

Edit: If you're asking if you can run a low pinion gearset in a high pinion axle I think the answer is NO.

 

[kmas0n]

Running a high pinion axle in the rear is on the weaker/coast side of the gear while running a low pinion in the rear you're on the stronger/drive side of the gear.

Edit: If you're asking if you can run a low pinion gearset in a high pinion axle I think the answer is NO.

So this is where I get confused... That mean a low pinion in the rear uses the drive side, but a low pinion in the front uses the coast side. So all the from Dana 30 axle use the coast side?

 

[macleanflood]

Well if you're planning on a Dana 30 for the rear why not make it rear steer?

-Mac

 

[Wildman]

So this is where I get confused... That mean a low pinion in the rear uses the drive side, but a low pinion in the front uses the coast side. So all the from Dana 30 axle use the coast side?

A low pinion Dana 30 would be on the drive side in the rear. The low pinion Dana 30 in a TJ in the front would on the cost side when going forward. But a high pinion axle in the rear would be driving on the coast side of the gear.

So all of us who have a high pinion Dana 60 in the rear of our Jeeps are driving on the coast side instead of the drive side of the ring gear. This technically makes it weaker. Because of the shape of the ring gear when using a HP axle in the rear the pinon gear is trying to push the ring gear away from the teeth on it. This is part of the reason why you use a load bolt on a HP rear axle.

Edit: For all this trouble I think you could find a newer LP Dana 44 axle and cut off the passenger side tube to get your width and weld a flange onto it. Do it right and you might be able to use a stock length axle shaft.

 

[kmas0n]

A low pinion Dana 30 would be on the drive side in the rear. The low pinion Dana 30 in a TJ in the front would on the cost side when going forward. But a high pinion axle in the rear would be driving on the coast side of the gear.

So all of us who have a high pinion Dana 60 in the rear of our Jeeps are driving on the coast side instead of the drive side of the ring gear. This technically makes it weaker. Because of the shape of the ring gear when using a HP axle in the rear the pinon gear is trying to push the ring gear away from the teeth on it. This is part of the reason why you use a load bolt on a HP rear axle.

Edit: For all this trouble I think you could find a newer LP Dana 44 axle and cut off the passenger side tube to get your width and weld a flange onto it. Do it right and you might be able to use a stock length axle shaft.

Thanks for the info. I think you are correct

 

[lBasket]

Why not LP 30 then if you're worried about being on the coast side

 

[hosejockey61]

So this is where I get confused... That mean a low pinion in the rear uses the drive side, but a low pinion in the front uses the coast side. So all the from Dana 30 axle use the coast side?

No. A high pinion axle in the front uses the drive side. A low pinion axle in the front uses the coast side. I high pinion axle in the rear uses the coast side whereas a low pinion axle in the rear uses the drive side.

 

[kmas0n]

Why not LP 30 then if you're worried about being on the coast side

I'm starting to realize it doesn't really matter if it's running on the coast side. I didn't realize that all of my jeeps are setup that way in the front already.

I liked the idea of a high pinion rear for a little ground clearance and easing drive-line angles.

 

[kmas0n]

Pictures!!!

I have a full build thread. I think the flat fender content starts around page 17

https://wranglertjforum.com/threads/trail_krawler-trail_willys.21015/page-17

 

[Woodrow]

I'm starting to realize it doesn't really matter if it's running on the coast side. I didn't realize that all of my jeeps are setup that way in the front already.

I liked the idea of a high pinion rear for a little ground clearance and easing drive-line angles.

Disclaimer: “I have no idea what I’m talking about”.

The high pinion is obviously a benefit for the driveline, as you said. I don’t know the ring gear size, shaft diameter and spline count for your D27 but I assume since you are considering it, the Dana 30 is better? If so, I think your idea may work well for your situation.

When driving forward, a HP differential in the rear is weaker for the same reason its stronger in the front. Conversely, when in reverse, the LP is stronger in the front and weaker in the rear. This is because on the coast side, under load, the pinion pushes the ring away which it does not or does less on the drive side under load. I don’t think that is likely much of an issue with your 60hp motor and relatively high overall gearing.

But your problem hasn’t been differential strength which brings up the question: can you get upgraded D27 shafts?

 

[kmas0n]

I cannot find anyone that's sells chromolly shafts for my axle. It's got a 7 1/8 " ring gear and 10 spline shafts.

 

[mrblaine]

I cannot find anyone that's sells chromolly shafts for my axle. It's got a 7 1/8 " ring gear and 10 spline shafts.

View attachment 656769

Have you checked with Dutchman?

 

[kmas0n]

Have you checked with Dutchman?

Thanks for the lead. It's not listed on their web site but I'll give them a call

 

[mrblaine]

Thanks for the lead. It's not listed on their web site but I'll give them a call

Barring that, what may be slightly less hen's teeth rare would be a rear Dana 44 out of a Roxor.

 

[kmas0n]

Ah, this is why I posted here... I never even thought about that. Thanks!

 

[bty34]

At one point I was looking at doing something similar, but ended up finding a CJ offset flanged 44 and gave up. It's been a little bit, but I thought the dimensions on a JK rear 44 worked out to allow narrowing only one side to get the correct offset and width.

Some of the cj2a page guys have been playing around with rear steer too.