Double cardan

[jjbird1120]

I had to replace a stolen front driveshaft on my 84k20. The used one I bought needs new ujoints and the double cardan thing fixed. I was looking for repair instructions. If anyone can help I would appreciate it.

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[crazy4offroad]

There are plastic plugs that need to be melted to get them out, and I think there are a couple different variants when it comes to the center pivot ball. Honestly taking it to a driveline shop will save you a lot of headache. I converted mine to a single joint like 76 and older had. There is also a mod to switch in a 2005 Dodge 2500 front dshaft if you wanted to upgrade to 1350 u-joints instead of the 3R's.

 

[MadOgre]

There are plastic plugs that need to be melted to get them out, and I think there are a couple different variants when it comes to the center pivot ball. Honestly taking it to a driveline shop will save you a lot of headache. I converted mine to a single joint like 76 and older had. There is also a mod to switch in a 2005 Dodge 2500 front dshaft if you wanted to upgrade to 1350 u-joints instead of the 3R's.

That's good to know! I did not know that. Thanks

 

[crazy4offroad]

Yeah I should clarify, the Dodge dshaft mod is NOT a direct swap. The flange at the tcase side is the same but the length needs shortened by a driveline shop (it is cheaper to shorten rather than lengthen a driveshaft). But it would have 1350 joints throughout, which means you might have to switch your pinion yoke. And that is not as easy as it may sound. There is a crush sleeve between the inner and outer bearings of the pinion, and as you tighten it, if the differential is still in place the pinion will want to "climb" the ring gear. You can get a combination joint, one side of the cross is 1350 and the other 3R but eventually you would want to change that. One other great benefit is the higher running angle, almost 35 degrees. Our stockers are nowhere near that, and if you've been trying to get the front driveline to be happy with 6 or more inches of lift the Dodge shaft might be the WTG.

 

[MadOgre]

Yeah I should clarify, the Dodge dshaft mod is NOT a direct swap. The flange at the tcase side is the same but the length needs shortened by a driveline shop (it is cheaper to shorten rather than lengthen a driveshaft). But it would have 1350 joints throughout, which means you might have to switch your pinion yoke. And that is not as easy as it may sound. There is a crush sleeve between the inner and outer bearings of the pinion, and as you tighten it, if the differential is still in place the pinion will want to "climb" the ring gear. You can get a combination joint, one side of the cross is 1350 and the other 3R but eventually you would want to change that. One other great benefit is the higher running angle, almost 35 degrees. Our stockers are nowhere near that, and if you've been trying to get the front driveline to be happy with 6 or more inches of lift the Dodge shaft might be the WTG.

How much longer is the Dodge shaft? With a 6" lift the stock GM shaft can be retained but it is to short to last more than a year or two. I put the longer slip yoke on it but it is still to short for 6". I end up rebuilding it every couple of years. And it really hasn't even seen that much use the last 5 years or so.

So if the Dodge shaft is only 1 or 2" too long then it would be perfect for a lifted truck with out mods ???

 

[crazy4offroad]

I'm not sure, not a mod I've done but wanted to do. I know that the SM465 holds the t-case a little closer to the front diff than an automatic and makes a sharper angle. Combine that with flexy springs and actually taking it offroad to do some crazy stuff and I was replacing front u-joints or busting parts every trip. So I built my front shaft out of 1/4" wall 2.5" square tube with a piece of 1/4" wall 2" square tube slid in for the slip yoke which works pretty well. But since changing to the TH-350 the front hasn't been an issue at all.