Should I upgrade my Dana 30 or just go with a Dana 44?


Steel City 06

TJ Expert
Supporting Member
Joined
Mar 12, 2019
Messages
3,853
Location
Pittsburgh, PA
So what are the proper safe ways to pull forwards or backwards w/o breaking things ?
Pulling forwards is a lot safer than pulling backwards, at least on the ring and pinion.

Ring and pinion gears are much stronger and also create more manageable stresses when the torque is applied to the drive side of the gears versus the coast side.

If you think about the angle of the gear teeth and also the angle of the mating faces, you can see why stresses are so much higher and in different places when the coast side is used to drive versus the drive side.
 

imahnu17

New Member
Supporting Member
Joined
Jun 1, 2021
Messages
22
Location
Houston, TX
Just to clarify, what you said above is true for a HP axle. However a LP axle would ride on the coast side going forward and the drive side in reverse.

That being said I still think it’s more advantageous (and safer in general) to pull going forward than in reverse.
 
  • Like
Reactions: SvtLdr

mrblaine

Easter Bunny
Supporting Member
Joined
Nov 20, 2015
Messages
16,465
Location
Quail Valley, CA
Pulling forwards is a lot safer than pulling backwards, at least on the ring and pinion.

Ring and pinion gears are much stronger and also create more manageable stresses when the torque is applied to the drive side of the gears versus the coast side.

If you think about the angle of the gear teeth and also the angle of the mating faces, you can see why stresses are so much higher and in different places when the coast side is used to drive versus the drive side.
Most don't understand or know the difference between the drive and coast sides and why that matters. It may be easier if they understand the tooth angle relative to the base of the ring gear on the drive side is 90 degrees. Driven on that side, the teeth stay engaged nicely under high loads. On the coast side, the tooth angle is sloped relative to the base of the ring so when driven on that side, the teeth are trying to push away from each other under load. If the axle housing isn't robust, then the teeth move away from each other out to the thinner cross section of the teeth which causes them to break.
 

Apparition

Next stop - The Rubicon
Supporting Member
Ride of the Month Winner
Joined
Jan 17, 2020
Messages
12,980
Location
Twin Cities, MN
Most don't understand or know the difference between the drive and coast sides and why that matters. It may be easier if they understand the tooth angle relative to the base of the ring gear on the drive side is 90 degrees. Driven on that side, the teeth stay engaged nicely under high loads. On the coast side, the tooth angle is sloped relative to the base of the ring so when driven on that side, the teeth are trying to push away from each other under load. If the axle housing isn't robust, then the teeth move away from each other out to the thinner cross section of the teeth which causes them to break.
Have you seen this to be a problem in the high pinion Rockjock axles or have they taken this into account in their housing design?
 

mrblaine

Easter Bunny
Supporting Member
Joined
Nov 20, 2015
Messages
16,465
Location
Quail Valley, CA
Have you seen this to be a problem in the high pinion Rockjock axles or have they taken this into account in their housing design?
The problem is typically solved by going to larger gear sets and robust castings with larger bearings. So, yes, it is still a problem but the problem is mitigated by adding lots of beef.

In perspective, the HP Dana 44 size gear sets are not robust enough to last long in a rear application on 35's in a TJ. Flip them around to the front and they work pretty well for 40's. The HP 60 stuff works very well for 40's in a rear application. Overkill for the front but other considerations are in play there.
 
  • Like
Reactions: Apparition
OP
J Harding

J Harding

Member
Supporting Member
Joined
May 30, 2021
Messages
25
Location
Valencia, CA
It is the same weaker in reverse that the LP 30 is in forward. Neither should be used to pull folks out if they are stuck hard enough to break something.

I watched a rig on a SoCal trail winching or trying to winch a guy out of a stuck on a small waterfall. He had his front tires against rocks but they started climbing. He put it in reverse to ease back some and get the front tires where they were in a better place. Broke both front axle u-joints and shredded the yokes. Don't do that.
Agree with @mrblaine. The issue is pulling someone when you are on a full traction surface such as asphalt or a granite surface. I pulled someone out of the sand with my CJ-2A on the street. I sheered one and bent the rest of the ring gear bolts. And I did it with the massive torque of a flathead 4 cylinder! When the Jeep is anchored to a stuck rig, the torque sent to a full traction surface and multiplied through low range can be deadly to your drivetrain.
 

srimes

TJ Enthusiast
Joined
May 19, 2021
Messages
102
Location
Oregon
The other reason to pull forward is that weight transfers to the rear axle, which is usually the stronger one. Pull backwards and now the weight transfers to the front axle, which is the acting rear. No one wants a dana 30 sized rear axle.
 

NashvilleTJ

I miss the snow...
Supporting Member
Joined
Sep 3, 2020
Messages
1,391
Location
Nashville
The problem is typically solved by going to larger gear sets and robust castings with larger bearings. So, yes, it is still a problem but the problem is mitigated by adding lots of beef.

In perspective, the HP Dana 44 size gear sets are not robust enough to last long in a rear application on 35's in a TJ. Flip them around to the front and they work pretty well for 40's. The HP 60 stuff works very well for 40's in a rear application. Overkill for the front but other considerations are in play there.
My experience with the HP 60 with 40’s in the rear was not good. Smoked the R&P twice. I’m now running a shaved 14 bolt, gave up some driveshaft clearance, and added some weight, but hopefully it holds up long term. So far so good after hammering on it a good bit.

I do think adding a load bolt, like the RockJock HP 70, helps a lot with the HP in the rear - and as you said the extra beef of the 70 contributes as well.
 

SvtLdr

Just a guy, with a Jeep
Supporting Member
Joined
Nov 26, 2019
Messages
744
Location
NE Indiana
If you get the big joint Revolution shafts, do not stay with 27 spline since that guarantees a break at the inner.
Have you seen or heard of anyone experiencing this? I understand the possible scenario but wonder if it's taking place out on the trail?
 

mrblaine

Easter Bunny
Supporting Member
Joined
Nov 20, 2015
Messages
16,465
Location
Quail Valley, CA
Have you seen or heard of anyone experiencing this? I understand the possible scenario but wonder if it's taking place out on the trail?
I have not seen it yet. What I have seen is many instances of broken 27 spline inners with the standard 5-760-X u-joint. So much so that we won't even run 27 spline inners because that is always a bad day. If we can break the 27 spline stuff with the standard u-joint, what chance does it have against the bigger joint and why make the inner the guaranteed weak link?
 
  • Like
Reactions: Modoc Guy

mrblaine

Easter Bunny
Supporting Member
Joined
Nov 20, 2015
Messages
16,465
Location
Quail Valley, CA
My experience with the HP 60 with 40’s in the rear was not good. Smoked the R&P twice. I’m now running a shaved 14 bolt, gave up some driveshaft clearance, and added some weight, but hopefully it holds up long term. So far so good after hammering on it a good bit.

I do think adding a load bolt, like the RockJock HP 70, helps a lot with the HP in the rear - and as you said the extra beef of the 70 contributes as well.
Stock and stock mod class can race on the HP 60. Legends steps up to the HP 60 and 70 VXR. I suspect you aren't being as hard on something as they are.
 

NashvilleTJ

I miss the snow...
Supporting Member
Joined
Sep 3, 2020
Messages
1,391
Location
Nashville
Stock and stock mod class can race on the HP 60. Legends steps up to the HP 60 and 70 VXR. I suspect you aren't being as hard on something as they are.
I’m certain that’s the case. I’m sure part of my issue is that my rig is likely a hell of a lot heavier, running similar horses (‘course, with that pig-14 back there I’m even heavier now...😬)
 

SvtLdr

Just a guy, with a Jeep
Supporting Member
Joined
Nov 26, 2019
Messages
744
Location
NE Indiana
I have not seen it yet. What I have seen is many instances of broken 27 spline inners with the standard 5-760-X u-joint. So much so that we won't even run 27 spline inners because that is always a bad day. If we can break the 27 spline stuff with the standard u-joint, what chance does it have against the bigger joint and why make the inner the guaranteed weak link?
Maybe a consolation for that bad day - if you end up breaking one, it's covered by a lifetime warranty! 👍