Non plunging inner CV joint on Front A-Arm suspension

LSTOYS

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I recently built a custom front suspension for my Colorado using Dana 44 front diff, Hummer H3 lower A-arms, custom uppers, 2500/3500 spindles, hubs, and CV axles. My initial goal was lots of ground clearance and strength. I am now thinking about re-doing some of the geometry to reduce axle plunge and gain more travel. I am looking at different options for CV axles at the same time.

My question is, is there a benefit to using non plunging 934 inner joints vs the 934.5 plunging? I know they have more angle, but since it's being used on a front application, will the outer steering joint be the limiting factor when using a 934 or stock chevy outer joint and a 934.5 plunging inner joint?
 

isdtbower

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The outer steering joint is "always" the limiting joint for angle. That joint also has to be precisely inline with the top and bottom ball joints. Maybe a plunging joint will self center there but ?????

It is best to design the IFS with "zero" plunge, but most still use plunging CV's at the inner. Your design, needs and wants will probably dictate what you can do. Most also design with the inner joint inline with the A-Arm pivots.

Smaller axles are used to help turning at the outer. Outer CV's will want to "turn" up to 45* and inners only-usually to 25* or less.

On rigs with big articulation (Ultra4) a larger Series 30 CV is used outside with a (relatively small) 35 spline axle. This allows close to 45* CV angle without the balls falling out, or the axle hitting the cup...and still stay strong. Most common is a series 30 CV on the inside but some are getting away with 934.5 CV's on the inside. These are big tire and HP rigs that take huge abuse from rock hits. The 35 spline axle also absorbs some of the shock, but many are using 40 spline stub shafts for durability.

Interesting to me are the Class1 cars and buggies complaining about CV heat. That is rarely, if ever an issue on Ultra4 IFS rigs. Even when run on the long desert races. I believe it is mostly about the large (inches) plunge the Class 1 cars have. I believe some of the Cl1 rigs have worked on that...and still staying strong.

All of this is informational, but some direction. It will be interesting the route the TT's take on this. Some are going the portal route for center ground clearance, use of the smaller CV's and axles, and less gear strength needed at the center. Hummer axles used to be pretty easy to break though....??
 

partybarge_pilot

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Stick with the 934 plunging inners. 934.5's will gain you nothing. Except added expense.......
 

LSTOYS

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I apologize, it has been a while since I had looked at the joint style naming conventions. I was thinking 934 was standard non plunging and 934.5 was plunging. I was not planning to go with 35 spline (934.5) For some reason I can't edit my original post now.
 

LSTOYS

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So if I'm understanding you correctly, if I have a non plunging 934 outter (40+ degrees of angle) and a plunging 934 inner (<25 degrees of angle), the outer will still be the limiting joint? I recall seeing a post from partybarge_pilot where he used non plunging 930 inner joints on a T100. Is there a reason for that? Also, some more info in case you have suggestions for a different joint size... I'm running 38" tires, dual transfercases, and a supercharged 6.0
 

isdtbower

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It sounds like more "rock crawling" here than open Dez. You might be coming from a straight axle background where 35-40* turning is "normal." With IFS you have to decide on the compromise between articulation, turn angle, and camber. (Not just turn angle) Much will depend on the length of your axle shaft which basically depends on the center diff width (CV-CV) and where you can place the outer CV in the upright. This is where a talented CAD guy can help before you even get started or moch something up before finishing-up too much. Steering and even boot clearance can be a got-ya. 38* IFS steering is huge, and 30* might be more towards normal. (Personally, I am building everything out of wood first to find those compromises and aw-Sh___s...even with some CAD help)

You will be asking a lot from a 934 & axle with a wedged 38", dual xfer, and 600hp....even without turning, etc. Put a thumb tack under your right foot. LOL...

Hang in there.
 

partybarge_pilot

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The outers on the T100 were non-plunging. They see more angle due to steering. The inners go 28* and the outers use all 40* when you figure in steering.
 

isdtbower

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Sorry. I should have gone back and read your original post again. I have a Dana 44 +Corvette IRS built in the 60-70's under a Jeep. The D44 flange width was either 17 or 21", and the overall tread width 76" This makes the half shafts about 12" long, and resulted in articulation about 8"...with U-joints. Actually the same set-up was tried in the front but ditched quickly for a SA because of the limited turning and compromises. With CV's you should be able to do better and still turn. When you get the pivots lined up with the CV's that will "fix" the plunge, but may not improve, or hinder the geometry. Cool that you got all that in the truck. And realize that the mods are no small project.
 

partybarge_pilot

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FWIW, an 8.8 out of a newer F150 would be a better choice than a D44. Easy to make center mount, lighter and stronger. 31 spline Exploder stub axles will fit with a little housing mod. The stubs will still be the weak link but stronger than anything for a D44.
 

LSTOYS

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I can't really go center mount. My low pinion Dana 44 diff is tucked up beside my oil pan for max ground clearance. It is using a pretty bullet proof selectable 33 spline OX locker, 8.9" thick JK dana 44 gears, and 33 spline OEM AAM 9.25 stub shafts from a Hummer H2. I did look into using an 8.8 though. I did not know the explorer stubs would fit. That is good info.
 
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