I've been going over my 2nd cousin Ruby's van and mostly doing routine maintenance. I took it to a muffler shop to have the flex joint fixed (rusted out at brackets, no surprise). I got a good look under it when it was up on the lift and noticed one outer cv boot needed replacing. The other outer boot was starting to go, so I thought I'd replace them both. After doing the driver's side, I started on the passenger's side and found the axle shaft was not the same. One axle shaft has a wedge-cut in the end and is shorter than the other. The spindle nuts were also different. The 4wd warning light has been flashing 3 times indicating a problem at the front axle speed sensor and I think the different axles are the cause. So, which axle shaft is correct?
I don't want to just slap it together (like the previous job); I want to fix it right. Can anybody tell from the attached photo which is right? Lower shaft with blue tape has tang-wedge (what do you call that?) and shorter threads on end.

 

Most catalogs list the same part number for both sides. However, there were different parts for the first year of the A4WD, 1990, vs 1991 and later models. But I think the critical length (between the outer spline and the inner flange) should be the same for all years, they should all be interchangeable. Some manufacturers list the same part for all years. The difference is that the 1990 model has U-joints on the inside end:

Product Detail

vs CV joints for the later models.

Product Detail

 

So the upper shaft (attachment to earlier post) is the correct one? I ordered a new shaft but the one I already replaced the boot on and put back on the van is apparently the wrong part! I think it is for a Windstar or something. The part I ordered is identical to the upper one, so I'll use the matching two axles and re-remove the other. Thanks for your info and if you have any pointers or advice, let me know.

 

Actually, your picture was too small for me to see any real difference between the two (couldn't tell what you meant by "tang-wedge"). I was just posting general information.

The Windstar takes different models (left/right specific), and they're different enough that I doubt either one will fit in an Aerostar.

More likely is one manufacturer made theirs slightly differently than stock. But as long as it properly installs and fastens, it should be OK.

 

Look on my profile/albums, the picture is much better.
The lower one has a channel cut into it so after you tourqe it to x ft/lbs you hit it with a punch to keep it in place...
I read that you weren't supposed to re-use the spindle bolts so I got new ones.

 

Sorry, I'm not seeing any pictures in your profile.

But yes, the axle nuts are usually torque-to-yield, so they can't be re-used. There are some that are a stack of thin nuts captured inside a cage, so that as you torque them down, they self-lock, so you don't need to do anything else to prevent them from loosening.