87 Mazda b2000, is my tranny gone? is my differential screwed? help me eliminate possibilities

mazda

#1

so, my truck will not move, and its wheels are locked. its a 1987 rwd mazda b2000. Its got only 70,000 miles on it (really) but it looks like a previous owner maybe used to tow with it.
I was driving it across the country, and when I started to go over the Rockies it started making a loud harmonic whining noise in 4th gear and at the beginning of 5th. The noise stopped while when I took my foot off the gas. I didn’t really have any choice but to keep driving it…unfortunately.
The noise kept getting worse and finally there was a loud thunking noise and I pulled the car over. After it stopped, the truck wouldn’t roll anywhere, the rear wheels were locked in place.
I called a guy to tow it and he pulled it up on the flatbed, the wheels made a couple more kind of popping noises and the wheels started turning again. when he dropped it off I tried putting it in gear and moving it a little bit- it seems like it wants to go, kind of beginning to roll a tiny bit, but it isnt actually able to go anywhere. The wheel are still locked, and its parked in a friend’s driveway. So, does this sound like the transmission? Does this sound like the differential?
I talked to a few mechanics before it actually completely broke and they all said it sounded like the transmission, but the tow truck driver said it sounded like it could be the differential… And someone said it might be the ujoint? The transmission makes the most sense to me, but I want to hear some other opinions if you’ve got em, and I’m sure you do!


#2

You can remove the driveshaft (a quick, easy job) and isolate where the problem is…This could be something as simple as a rear wheel bearing…You might check the fluid levels in both gearboxes while you are at it…


#3

If when you are trying to move it, the drive shaft turns , your differential is gone. If your drive shaft isn’t turning, then your transmission, clutch or crankshaft is broken. You say you didn’t have a choice but to keep going. You always have a choice to stop and get something fixed, after all, you are stopped now.


#4

More than likely the transmission is in 2 gears at the same time…


#5

If the rear wheels won’t turn, and then there was popping sound when pulling it onto the hauler and then the wheels turned means the rear differential is damaged.

Tester


#6

Two gears at the same time is possible. If part of one of the internal shift rods is broken it could happen. You can see the rear ones when you remove the tail housing from the transmission but don’t remove it yet.

Before you do that, remove the shifter and see if the plastic doober on the end is broken. Put trans in neutral first. When the shifter is out you might be able to move the shifting rods into neutral by pushing on the fingers on the end of them.

You will know they are in neutral if the truck can be rolled back and forth. Then bolt the shifter back on and see if things work.

If the thunking noise is meaningful, a used transmission shipped will cost about $400 or less.