Rear Axle Perch Fix for Open Driveline AD's

[mcgillis]

My 1953 3100 with later 10-bolt open driveshaft has the rear wheels 3" forward of the fender opening centerline. Is there an easy fix for this?
Thanks,
Dennis

[Deve]

Hi Dennis! The way I fix this is make a 1/4" steel plate that is the width of the leaf springs and about 4-1/2 or 5 inches long. Decide where you want the rear axle to set and measure that distance. Usually about 3 inches. If its more than that, make the plate longer. Drill a 7/16" hole about 1/2" from one of the long ends and then do the same for the other end (so there is a '3 inch' difference between them). In one of the holes, weld a stud that sticks up about 1/4". That stud fits in the rear ends spring perch hole. The hole on the other end fits over the springs nub. Make two of those and that is about as easy as I can think of. We all have to do that whenever we are using an 55-59 GM open driveline on our 47-53 AD's because the original spring perch is not in the center.

I measure to find the dead center of the leaf spring. This is where you center the rear axle. This is how you determine exactly the measurement (3 inches might be 2-3/4 or so) Good luck! The other option if your springs are IFFY anyway, is to have the local spring company make you a set using the 1954-1955 template (spring perch in the dead center of the spring).

[mcgillis]

Hi Deve! Your steel plate idea sounds easy enough.
Step two must be to take my driveshaft to a pro and have it stretched to the proper length?
Thanks,
Dennis

[Deve]

Yeah. That is true. Sorry. I knew what I had to do beforehand so had the 62 Suburban driveshaft cut to length after it was already set. But there are many driveshaft companies out there that will do that for you. I do not recommend doing it yourself since there is a balance issue involved. The takeaway here is... the 62 Suburban (and probably surrounding years) driveshaft is long enough to cut DOWN to fit. They are 3 inch driveshafts.

[Pre68Dave]

The wheels appeared to be ahead of center in the fender originally, but not 3".
If you set the axle so the wheels are centered in the fender you may find the e' brake cables will be to short.

[Deve]

Because of the way the torque tube was designed, it had a rotator assembly (for lack of what it's really called) that placed it forward without it really being forward. You have to really look at the difference to see how the design came into play. So in the end, the cables hook up just fine. It took me awhile just staring at it for awhile to see how they did it. I didn't have to change the e-brake cable adjustments at all. The adjustments are right in the center. Since this was changed in 1955 with the open driveline, and the e-brake cables are good through the AD years, it all works out. There is even a bonus when going to a 55-59 rear end.. Bendix brakes! But yeah, the difference between the 47-54 and 55 spring perches are 2-3/4" or so. If I recall, the perches for the 47-54 are 26-3/4" from the rear spring mount and the 55 are 24 inches (centered exactly). I don't think it changes where the actual axle is placed. Its the way it was mounted. Personally, I replace the springs with the 55 design (perch in the center) whenever I do that change. The plate works great though!

Dave has a point when it comes to arbitrarily deciding to move the wheels to a non-stock position. The e-brake cables may not reach.

[MO54Frank]

I think it is necessary to weld up the "rotators"/ brackets since you no longer have the torque-tube to keep the axle from rotating.

[Deve]

The entire rotator issue goes away when you scrap the rear end for the newer style. Keep just the springs and get rid of everything else, then either make an adapter plate or get new springs altogether. Since these springs are easily obtainable new, most people scrap the old springs because they are so badly worn. If you are lucky enough that yours are salvageable, the adapter plate works great.

[MO54Frank]

Old thread. It’s been a long time since I have been on this forum. Of course you are correct Deve. Thanks for providing good info.