RCV axle shafts or chromoly for PR44
- Thread starter nmwranglerx
- Start date
blazer
Caught the Bug
Hey, yes, exactly what I found, too.
And...see 147 is only for 3.73 gearing and below.
I have 5.13's like alot of us do.
So.....need to find out what problems there will
be with the 157's. Probably will head down to HB
tomorrow morning and ask in person about the issues.
Any thoughts????
And...see 147 is only for 3.73 gearing and below.
I have 5.13's like alot of us do.
So.....need to find out what problems there will
be with the 157's. Probably will head down to HB
tomorrow morning and ask in person about the issues.
Any thoughts????
Dynatrac
-
I’m going to agree with everybody in one way or another, but maybe add some detail. Much of the facts have already come out.
LoPo’s post with the link get’s you as close to a bible about ProRock 44’s and stock TJ and JK 44’s that I know of. I’ll bet there are more good ones created by others since. Here are our links so you don’t have to look back. Read them carefully.
http://www.dynatrac.com/products/jk/pro-rock44.html
http://www.dynatrac.com/pdfs/ProRock FAQ_revK.pdf
http://www.dynatrac.com/pdfs/New_Gen_D44_comparison_chart.pdf
http://www.dynatrac.com/pdfs/Choosing_the_right_housing_revC.pdf
We put a lot of time into the documents to help folk’s make better decisions. When we released the ProRock 44 and published our documentation, literally every aftermarket JK shaft made, was the wrong length. That’s what happens when you send parts to China and India to be copied cheaply. Lot’s of folks have problems because the shafts they bought were wrong. Hopefully most have now been corrected after we published our engineering data for the ProRock 44. FYI – the JK Rubicon 44F’s require a much tighter tolerance for shaft length. Not sure everybody in the aftermarket shaft biz out there knows that, or can even do it.
Wayalife is correct in that the RCV’s are very strong, and are less likely to fail at the joint than a traditional U-joint. This is due to the materials chosen by RCV, and the good USA-made quality they provide. RCV shafts do not bind in tight turns. This is due to the best feature of any CV, which is that it provides “uniform rotational output” at all positions.
The conventional U-joint front shaft is also known as a “single-cardan” configuration. The single U-joint allows the shaft to “steer”. The downside is that as you rotate the inner shaft at a constant RPM, the outside shaft RPM varies slightly when it increases in turning angle. The more the angle of turn, the more the output variation. This is called “non-uniform rotational output”. So it makes your tire speed up and slow down just a little bit, every rotation. At the shaft it is not very significant, but at the outside of a large diameter tire, it becomes more significant. That’s the binding you feel when turning in 4WD on hard surfaces. The RCV shaft will not exhibit the same binding in this case.
A double-cardan axle joint is more commonly used in heavy and military 4x4 trucks because they have very large tires, and the vehicles are incredibly heavy. The non-uniform output of the single-cardan is too harsh on the rest of the axle with such high traction. By putting two U-joints back to back, they cancel out each other’s variation of speed, and you get the same uniform rotational output as you would with a CV. Ordinary Driveshaft’s have the same limitation, which is why you have to phase the joints at each end correctly, or you lose the cancelling effect.
U-joint shafts are less expensive than RCV’s as pointed out by Northridge. The quality of most aftermarket shafts also varies widely. 4340 from India and China, is not the same as 4340 from the US, Europe or Japan. Neither is the quality of forgings, heat treating, dimensions and general workmanship. We have studied many imported shafts and found shocking things like huge voids inside the steel of a forging, no heat treat, and 2-piece welded construction. We also found lots of dimensional defects like taper in the U-joint bores. U-joint bores not square to the centerline, U-joint bores not concentric with one another, etc. These are geometric relationships that are difficult for someone with a Mic or caliper to detect, but are not uncommon in imported shafts we have tested. Out of a 50-100 piece sample lot, up to 75% fail the inspection for more than one reason. Many of the defects cannot be detected without destroying the part. But the good news is that these shafts are “cheap”, and the sellers will assure you their 3rd world manufacturer is the “best”. 2 words for you - Buyer Beware.
If you have a stock Rubicon 44F and want to install 35-spline shafts, you must use the RD157. Rubicon 44F housings are unique in 2-ways. The center pin of the Tru-Loc diff is offset to one side, and the Carrier bearings are slightly different size than earlier model 44’s. The RD157 is the only diff I know of that fits the Factory Rubicon Housing (carrier bearings) and has the 35-spline feature. We offer 2 variations of ProRock 44’s. One for Tru-loc factory Rubicon diffs, and one for conventional 44 (everything else) diffs. Think and plan ahead, they are not interchangeable later. The Tru-loc is a great device, but not the most durable. If you’re building a JK with 37’s or larger tires, consider switching to the ProRock, a new aftermarket diff, and shafts to match at the same time. Yes, that is more expensive. If you are a more mild trail guy, and on 37’s or smaller tires, the Tru-Loc in your Rubicon should last the life of your vehicle. Side note. A replacement Tru-Loc diff for your front Rubicon 44F at the dealer will set you back $1,920.00 MSRP. WOW!!
We designed the ProRock 44 to use the RD147 for 35 spline applications, which our tests have shown is a better fit in the housing. ARB is a good proven product, and a good company. Ox, Eaton and Auburn Gear are emerging with new diffs that are electrically activated. We enjoy excellent relationships with all 4 vendors. Each offers advantages. The choice is yours.
Hope this helps y’all.
LoPo’s post with the link get’s you as close to a bible about ProRock 44’s and stock TJ and JK 44’s that I know of. I’ll bet there are more good ones created by others since. Here are our links so you don’t have to look back. Read them carefully.
http://www.dynatrac.com/products/jk/pro-rock44.html
http://www.dynatrac.com/pdfs/ProRock FAQ_revK.pdf
http://www.dynatrac.com/pdfs/New_Gen_D44_comparison_chart.pdf
http://www.dynatrac.com/pdfs/Choosing_the_right_housing_revC.pdf
We put a lot of time into the documents to help folk’s make better decisions. When we released the ProRock 44 and published our documentation, literally every aftermarket JK shaft made, was the wrong length. That’s what happens when you send parts to China and India to be copied cheaply. Lot’s of folks have problems because the shafts they bought were wrong. Hopefully most have now been corrected after we published our engineering data for the ProRock 44. FYI – the JK Rubicon 44F’s require a much tighter tolerance for shaft length. Not sure everybody in the aftermarket shaft biz out there knows that, or can even do it.
Wayalife is correct in that the RCV’s are very strong, and are less likely to fail at the joint than a traditional U-joint. This is due to the materials chosen by RCV, and the good USA-made quality they provide. RCV shafts do not bind in tight turns. This is due to the best feature of any CV, which is that it provides “uniform rotational output” at all positions.
The conventional U-joint front shaft is also known as a “single-cardan” configuration. The single U-joint allows the shaft to “steer”. The downside is that as you rotate the inner shaft at a constant RPM, the outside shaft RPM varies slightly when it increases in turning angle. The more the angle of turn, the more the output variation. This is called “non-uniform rotational output”. So it makes your tire speed up and slow down just a little bit, every rotation. At the shaft it is not very significant, but at the outside of a large diameter tire, it becomes more significant. That’s the binding you feel when turning in 4WD on hard surfaces. The RCV shaft will not exhibit the same binding in this case.
A double-cardan axle joint is more commonly used in heavy and military 4x4 trucks because they have very large tires, and the vehicles are incredibly heavy. The non-uniform output of the single-cardan is too harsh on the rest of the axle with such high traction. By putting two U-joints back to back, they cancel out each other’s variation of speed, and you get the same uniform rotational output as you would with a CV. Ordinary Driveshaft’s have the same limitation, which is why you have to phase the joints at each end correctly, or you lose the cancelling effect.
U-joint shafts are less expensive than RCV’s as pointed out by Northridge. The quality of most aftermarket shafts also varies widely. 4340 from India and China, is not the same as 4340 from the US, Europe or Japan. Neither is the quality of forgings, heat treating, dimensions and general workmanship. We have studied many imported shafts and found shocking things like huge voids inside the steel of a forging, no heat treat, and 2-piece welded construction. We also found lots of dimensional defects like taper in the U-joint bores. U-joint bores not square to the centerline, U-joint bores not concentric with one another, etc. These are geometric relationships that are difficult for someone with a Mic or caliper to detect, but are not uncommon in imported shafts we have tested. Out of a 50-100 piece sample lot, up to 75% fail the inspection for more than one reason. Many of the defects cannot be detected without destroying the part. But the good news is that these shafts are “cheap”, and the sellers will assure you their 3rd world manufacturer is the “best”. 2 words for you - Buyer Beware.
If you have a stock Rubicon 44F and want to install 35-spline shafts, you must use the RD157. Rubicon 44F housings are unique in 2-ways. The center pin of the Tru-Loc diff is offset to one side, and the Carrier bearings are slightly different size than earlier model 44’s. The RD157 is the only diff I know of that fits the Factory Rubicon Housing (carrier bearings) and has the 35-spline feature. We offer 2 variations of ProRock 44’s. One for Tru-loc factory Rubicon diffs, and one for conventional 44 (everything else) diffs. Think and plan ahead, they are not interchangeable later. The Tru-loc is a great device, but not the most durable. If you’re building a JK with 37’s or larger tires, consider switching to the ProRock, a new aftermarket diff, and shafts to match at the same time. Yes, that is more expensive. If you are a more mild trail guy, and on 37’s or smaller tires, the Tru-Loc in your Rubicon should last the life of your vehicle. Side note. A replacement Tru-Loc diff for your front Rubicon 44F at the dealer will set you back $1,920.00 MSRP. WOW!!
We designed the ProRock 44 to use the RD147 for 35 spline applications, which our tests have shown is a better fit in the housing. ARB is a good proven product, and a good company. Ox, Eaton and Auburn Gear are emerging with new diffs that are electrically activated. We enjoy excellent relationships with all 4 vendors. Each offers advantages. The choice is yours.
Hope this helps y’all.
Christarp
Member
Definitely bookmarking this post for future reference.. Thanks for the massive amount of knowledge you bring to the forums you guys are on!
Charlie Mike
New member
I know I want to go PR44 in the future. So every time I see a thread discussing the PR44 I subscribe to it. This has been the most informative thread by far! This will be extremely helpful. Thanks Dynatrac! :thumb:
nmwranglerx
Caught the Bug
Awesome info from Dynatrac rep, thanks for posting!