Turning radius

Hi guys, can anyone tell me the actual turning radius (in feet) for both the dana 25 and dana 30 axles?

I was doing some work around the property this past weekend and the huge turning radius of my closed knuckle axle had me wishing I had the dana 30 that is currently sitting in my shed ready to go. I need to swap the gears out for 5.38's and spruce it up.
I did a search but couldn't come up with any hard numbers.... I'm wondering if I should bump this swap up on my priority list, as I'm doing a lot of close/twisty work in my back woods and it sucks making 3 point turns every 2 minutes. chainsawguy

 

so, if you had to choose between saving for an overdrive and doing the dana 30 swap, which one would you choose first?

 

Time to set the record straight !

The D30 has a maximum allowable steering angle adjustment of 27-1/2*.
The D25 and D27 both have maximum allowable steering angles that are dependant upon which axle shafts are installed.
Bendix = 23*
Rzeppa = 29*
Spicer = 27-1/2*

The additional width (2") of the D30 sets the tire away from the frame.

 

........and away from the spring. So you can tighter before the tire makes contact with the spring. Essentially, the extra width of the 30 allows you to use all, or at least more, of that 27 1/2* before the tires hits the spring. This is what actually allows for better turning radius.

 

Hmmmm..... so if I installed Rzeppa shafts and wheel spacers.... technically I could get an even tighter turning radius than the 30? (taking out calculator)....


right now my Jeep is just a toy, I live in the country but have yet to find any trails to ride on. The main road from my house is 60mph in both directions before hitting civilization so an OD is pretty high on my list of priorities. I have been, however, using my jeep as a log skidder on my property and the turning radius is horrible! Decisions, decisions.....

Just did a search for new axleshafts, found some with spicer joints at ~$190 a piece!!! Looks like a D30 swap isn't looking that expensive after all

 

A 1" wheel spacer won't give you as much clearance as having the steering pivot out 1" further.

 

I would not jump to any conclusions about this. Conventional wisdom says that the open knuckle and wider track will provide a smaller turning radius. This was a specific objective for the new axles - smaller turning radius was listed as a feature in the sales literature.

My understanding of Ken's figures says that the different shafts will give you a larger theoretical angle for breaking (maybe reliable operation under load? Something like that), if there are no other limits to the turning angle. Certainly Rzeppa joints will do you no good if your tire hits the spring at 21 degrees angle.

Also be aware of the considerable improvement in maintenance and durability issues. Seems like a no-brainer to me, if you are capable of doing the swap and can afford it.

 

Also, you can get a little tighter radius by adjusting the axle stops. Adjust them too much and your tires will hit the springs - this does nothing bad, but makes a cogging noise as the tread rubs over the springs, and may be disturbing to some. Doesn't really hurt anything though.

 

kind of like putting a playing card and a clothes pin on the frame of your bike.

 

JMO - the 25 and 27 are fine operationally. If my only objection was the turning radius, I'd do the overdrive first.

 

I run Rzeppa in my D25 front but can not get 29* of steering angle if used with oversized tires or inset wheels.
Oversized tires on my jeep are any tire beyond the early standard 6.00 x 16".
6.00 x 16 are roughly 28.5" diameter.

Original front axle shafts for a 1957 CJ-5 are of the Spicer type and the standard tire for that vintage is also the 6.00 x 16".
Set to maximum 27-1/2* steering angle you can install 6.50 x 16 tires without spring rubbing.
6.50 x 16" are roughly 29.5" diameter.

Factors effecting spring rub are:
1) Wheel set (effects track width)
2) Tire width (effects tire inset)
3) Tire diameter
4) Which type axle shafts are installed for D25 or D 27 only (determines maximum turning angle)
5) Axle width and knuckle pivot width (effects track width)
6) Possibly suspension modifications (least common condition)

 

Here are the numbers I recorded from my D27 to D30 upgrade. I have 33 x 10.50 tires mounted on 7" wide Renegade oval slots. The claim that you can turn a circle with a Dana 30 inside the circle with a Dana 27 is valid. My tires touching the springs are the limiting turning factor with both axles.
I could turn a 36’ diameter circle with the D27. I’m down to 25’ with the D30. These measurements were from the inside track.
If you add two widths of the CJ to 25’, there’s just a bit left over before you get back to 36’.

 

that's exactly what I was looking for, thanks!

 

As it stands right now, I'm running 31x10.5x15's on stock suspension. I'm not sure what type of shafts are in there right now, but my tires just rub when turning full left.
The main thing that has me hesitant about the swap is having to redo the gearing, which I have never done, and all of the steering complications that I've read about. Although I wouldn't mind saginaw steering, I would like to keep the ross box for now. I also don't want to have to get a new driveshaft right away either, which I've read might be necessary.
I have never welded either, so I'm not sure about moving spring perches and such. The search function comes up with pages upon pages of threads so it is hard to get a handle on the scope of the project!

 

No need to move spring perches they line up right. You need new spring plates because the 30 has larger axle tubes. And the 30 will help if your limiting factor is the tires on the frame since it is wider.

 

I have seen that page, and it has lots of great information, but I'm not a mechanic by any means, and could really use a step 1,2,3 type guide with a lot of pictures to help me through the process. Something along the lines of Rick Stiver's t90 rebuild guide. Does anyone know of a good thread that documents the swap in detail?
For example, a few people have said that I need to shorten my draglink in order to use my ross box. How do I go about that!?!?!?! I guess I'm mostly hesitant about pulling my operational dana 25 axle and then opening a can of worms.

 

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