1971 Blazer: Need Driveshaft Advice

[ArchLAB]

400c.u.
3-Speed Saginaw /Dana20

Hi. Recently my '71 Blazer started clangin' like heyll from the Transmission Area. I assumed that the Saginaw had failed & was throwing pieces of gear around in the case.

Well, to my (hopefully) 'pleasant surprise' it looks like the issue was that e U-Joint (or rather a U-J retainer) had failed going from the rear driveshaft into the Transfer Case. As such, the driveshaft was whipping around on only 2/of 4/connect points.

If I'm lucky, all I need to do is replaced e the U-J & retainers. However, my rear DrvShaft looks to have been fabb'd by so e half-axxed hack (rough welds, who knows what else). I think that for the long term, I need to replace this DrvShaft.

1). DRIVESHAFT SWAP: I am looking g at some replacemnt options ,& am interested in using an aluminium shaft from a donor.

Also, I have a line on the front & rear DrvShafts from an '02 Silverado for $80: Is this, or something like it a viable option?

I'd like to upgrade to something better. My Driving would be 80% City/Hwy & 20% light-medium off-road.

1a). How much would YOU pay to Swap to different shafts? Will these need tobe
reworked/balanced for my truck?

1b) If the 'hack-job' DrvShaft that I have can be reworked/balanced d, how much would
YOU pay for that?

2) INTERCHANGE ISSUES?: BTW, I may consider swapping out the Transmission/Transfer Case for something less 'rudimentary' than the Saginaw 3-speed for a more 'gentlemanly' 700r4...or even a 4-speed Manual (Sag, Muncice, BW). Would there be interchange issues there?

Thanks for

 

[6872xtc]

I wouldn't spend the money to modify the shaft from the '02, since it probably won't fit your yokes, and it will most likely cost more just to shorten it.
The t-case is what will determine more of what you need for driveshafts. They can make a steel shaft do what you need, even with an overdrive.
Just my .02....

 

[diesel4me]

The transmission swap depends on how the existing Saginaw 3 speed connects to the transfer case..it most likely bolts right to it (or a short adapter),and if that is the case,I'm not sure if GM used a "special" 4x4 output shaft in the 3 speed,or simply used a typical 2wd transmission with no tail housing--if that was true,then a Saginaw 4 speed might bolt in its place--never tried that myself,or know of anyone who did--I have seen only maybe a half dozen trucks with the 3 speed 4x4 Dana 20 setup..

Years ago I looked into putting a M-22 Muncie in my '72 K5,Advanced Adapters did sell a conversion kit ,but it was over $600,I decided the SM465 was stronger and cheaper,easy to find then too..I bought everything from a donor truck for $300 to do the swap ,from a guy with a '72 like mine he totaled..
(After the swap was done I hated the wide spacing between second and third,with 3:08 gearing,it was doggy and lugged a lot..I would have liked the Muncie much better!)..

I think the gear spacing in an SM465 in second,third and fourth,is about the same as the three gears in your 3 speed..

A SM465 swap would require probably "everything"--bell housing,tranny,transfer case..when I swapped one in place of a TH350/NP205 in my '72 K5 years ago,the front drive shaft was now too long,I scored a 23" one off a '69 K20 that was a one year only version,after that they went with one 27" or so long--the rear shaft fit fine though..

Many "later model" drive shafts are aluminum and carbon fiber combo's,I'm not sure if those can be altered...a drive shaft is a hard thing to find used around here--few salvage yards attempt to save any,most get ruined when they pick up a vehicle with a forklift..

If your lucky enough to have an old boneyard that has a stack of them piled up,a tape measure and a old u-joint to match up may gain you one that will fit "as-is"...even if its off some other vehicle,if the u-joints are the same,it'll work,and they do sell "conversion" u-joints that let you mate things that are different too..