Ujoint small vs. Large Debate.

Re: 1966 CJ-5 front driveshaft

Not in the driveshaft's shaft area you can't, but the transfer case front output yoke is the same size as the driveshaft yoke since converstion u-joints weren't used and the continued use of the combo in FSJ applications with 1310's for years pretty much shows that there couldn't have been a yoke clearance problem with a D20 and a TH400.

 

I think it wasn't mentioned because you don't need a smaller yoke to do those things. Refer to the later CJ front driveshafts of the "rod" design with 1310 joints (which are undesireable for obvious reasons). I may still have one of these at home to photograph and compare OD's against the 66 shaft I have listed.

True in the case of shaft clearance to the bell, starter, etc and I agree on that part. However, the angle that the driveshaft departs the transfer case has no impact on yoke clearance. Regardless of where the front diff is located, the D20's front output does not move relative to the transmission. The OD of the yoke is still the maximum OD of the driveshaft assembly and its position does not change. If anything, it only gets bigger in the case of a FSJ with a double-cardan joint at the transfer case.

 

I already posted why I think they were used at the end of post #13. Nobody answered the question about when the small joints disappeared, so I am proceeding under the assumption that the last year of the 5-105X joint was 1971.

With the introduction of the 225's additional power and heavy flywheel, my personal theory is that the smaller joints has nothing to do with clearance at all. They are functional fuses that only appeared on the V6 vehicles due to the V6's ability to break the D27 internals. They appeared in 1966 with the V6 and disappeared (as far as I can tell) with the introduction of the D30 in 1972 when the risk was then mitigated. The CJ's and Commandos used the D27 for the same year range, so the theory equally applies to both lines. I believe they were meant to be failure points by design - to ensure that something cheap and easy to replace broke prior to something complex and expensive, as Jeep knew they were giving owners an engine that could break the axle much more easily than before.


The point of this (where it leads and what it means for V6 owners) is that there may in fact be no reason why a 1310 yoke upgrade can't be made to a D18 or D20 front output in conjunction with a D30 swap to make the effort a more beneficial upgrade overall. That's why I'm asking for all the nay-sayers to post some kind of proof. If the clearance issue truly does not exist and I were to go through the trouble to install a disc'd D30 in my ECJ5 or Commando, I would opt to buy the 1310 yoke for the case and run a better shaft, not the 5-105X yoke for the axle and be stuck with tiny joints.

 

Here's some facts to add. I just did a dana 30 swap in Pete. I also purchased a new driveshaft from Tom Woods w/ 1310 joints at both ends. There was no clearance issues w/ the d18 yoke or the joints. I had a slight clearance problem w/ my exhaust because it is routed above the driveshaft tube. That was remedied w/ a little flex(dented enough to clear), otherwise plenty of clearance(3" lift).
In regards to the small shaft being a fusible link, I can't see it. Even a small shaft can over power the D27. I've busted 3 sets of spider gears w/ the one laying in my shed and its never had a u-joint replaced in it.:v6:

 

If you don't like the little fellers then don't run em. I swap them out just cause I dont want to carry two sizes of spares. Breakage is almost always controlled by the amount of pressure placed on the pedal under your right foot.

 

Re: 1966 CJ-5 front driveshaft

I think the answer is right there, I think you can have a 1" driveshaft tube and a honkin big yoke, once it's welded on it isn't going anywhere. Hitting the yoke on the trans makes sense.

 

Re: 1966 CJ-5 front driveshaft

I was thinking it didn't make sense because of what you just said - it isn't going anywhere. Even if some Commando's had a 2-piece shaft, the 1st yoke would still be in the same place. The shaft angle can change, but the yoke does not move crosscar or fore/aft at all. The transfer case front output is fixed. It has no slip yoke like YJ's/TJ's/XJ's/ZJ's have in the rear. We already know that larger-jointed variants of the same driveshaft combo exist in FSJ's and don't have a Dana 20 output or driveshaft yoke interference with the TH400.

Revisiting this picture, the yoke isn't really near the pan. Its located fairly to the rear, above the pan, and good few inches outboard of the pan. I'm going to work on finding better shots, though - ideally with a shaft present. The shaft shown in this picture does not look like it belongs with that drivetrain. Perhaps the owner of that pic can provide more, or at least larger ones.

 

for what its worth the 1970 cj that i parted out was f-134 and had the small joints in it. i thought it was just because it was a civilian model, both of the m38a1's had the larger joint

 

To understand individual changes one must observe the overall progression.
Bear with me here these are the facts as I understand them to be.

The complete story really begins with the prototype reconnaissance vehicle.
All entries produced during early development relied almost entirely on Spicer drive train components.
Furthermore all military prototypes vehicles used the Spicer built model 25 front axle.
That axle progressed yet changed very little throughout its production.
It always used the W/O # A 1106 End Yoke.

In 1961 W/O began to install the new model 27 front axles into the CJ's.
The model 27 Spicer was very short lived.
It was back out of production that same year.
By late 1962 the model 27 re-emerged as the model 27A.
This version amounted to little more than a change of the housing cover.
Both 27 and 27A used the W/O # 926816 End Yoke.

Then in 1965 the axle was changed again and became known as the model 27AF.
In its final form the axle was now fitted with the W/O # 936216 End Yoke.
According to numerical parts reference the model 27AF seems to have arrived immediately before the V-6 became available.
All later CJ's both F-4 and V-6 versions through 1971 had the W/O # 936216 End Yoke.

 

My stock v6 jeep had the drive shaft hitting the starter in this picture. And don't tell me about the rust, I know its there.

 

My '66 CJ5 did too. I gave the front shaft to another guy and the ujoints were too small.