Well I took the first road test in the El Camino this morning, made it about ½ mile and ended up bringing it home on a tow strap.

I was taking it very easy on the truck, checking to make sure the transmission shifted ok etc. Everything started out great until I went around a corner the truck down shifted and all the sudden there was a small pop and a whining sound and forward movement stopped. It felt like the transmission was suddenly slipping badly. You could feel it try to kind of pull in both low and reverse but it was not able to overcome even a very slight slope.

Fortunately a friend of mine was around and towed me back to the shop. What we found when we got it back was that the drive shaft was turning but the wheels weren’t (on the bright side it at least it beats having to R&R the transmission).

The rear end is a 59 Ford SW 9” It was a complete drum to drum pull out that originally had an open 3.50 carrier in it (as it was already out and all I was going to be re-using was the housing, axels and brakes I there was no chance or need to road test it). The differential is one I picked up from a friend and had rebuilt prior to installing it. It’s a 2 pinions Traction-loc differential and 2.75 gears.. As I said there were no loud noises, grinding or jerks and popping when it stopped working like I would have expected if I had knocked some teeth off something.

I pulled the third member out and tore the Traction-Loc apart. Other than the clutches being kind of ugly now there is no obvious signs of damage; no broken teeth on the ring and pinion or spider gears, no chewed up splines on the axels and the axel bearings are still fully seated.

I’ve been around Posi units with burned up clutches in the past and they basically just act like an open rear end, this one doesn’t will barley move the truck on level ground.

Has anybody else run into this before and have an idea on what’s not right?

. About the only thing I can come up with it one or both of the axes are too short and only engaging the clutch hub (thrying to transfer all the power thru the clutches) and not the spider gear(s). I’ve never heard of different axels between posi and non-posi units…..but I suppose it is possible that at some point one or both axes have been changed in the 40 years since this axel was built.