Is the differential on a 1977-78 macho power wagon with an np203 a locking or open differential? Please Explain.

locking differential in the rear would have been a "sure-grip" unit, and available at extra cost. the owners manual would do a much better job at describing it than I could...same goes for the "LOC" position on the t-case lever....which is for the 4wd portion of the t-case only....

Front and rear differentials are open on most Dodge '72-'79 4x4s. Sure-Grip was an a Factory Option for "locking" (slowing down the spin) on one REAR axle wheel when traction was lost by the other rear wheel.

Sure-Grip was only installed on the rear differential on all Chrysler model lines.....

Now if you would have said "if there was a locking differential on the 78-79 Little Red Express", I would say, many of those trucks had the Sure-Grip option.........

Not many had the Sure-Grip option on the Dodge 4X4s.

How can you tell if you have Sure-Grip without taking the back inspection cover off the rear differential?..... Jack the Truck up in the rear untill the rear wheels are not touching ground. Jack stands under the frame area & block the front wheels & engine is NOT RUNNING! Put the transfer case shifter in neutral. Have a buddy take a hold of one rear wheel. You take the other wheel and turn clock wise. If your buddy is holding the wheel, it should be turning clockwise too. If he trys to stop the clockwise motion you should feel the same exertion on your wheel while your are still turning clockwise.
Hope That Helps,

Wow! Thanks, you guys really helped alot. Now, my rear diff is a 9.25, and I know the usual on the macho's were 8 and 3/4, right? So do you think that becasue my diff was upgraded to a 9.25, that it's most likely a locking diff? Because my mopar collecting cousin used to have a 78 power wagon ( regular, not macho ) with a 9.25, and he said his was open diff.

9.25 in most common in W150 Dodge/Plymouth TD 4x4s. Sure-Grip "still had to be special ordered"....... 8.75 in light duty for six cylinder/318 D,W, 100s

starting in 1978, the 8 3/8 rear axle was standard on the W100 and W150 models. I have had many with the little rear axle in them. It seems like anything that had 3.21 axle ratio without sure grip had the small rear axle. The ramchargers almost always got the 9 1/4 axle.
I have had several 400 and 440 W150's that had the small axle in them with 3.21 gearing....the 79's were more common with the little rear axle too...

You mean the small axle was the 8 1/4" rear with the 10bolt round cover right? The same as most light duty RWD cars from the 70s/80s. It seems like the 8 3/4" with the dropout carrier went up to '73 maybe '74 1/2ton trucks? Then the 8 1/4" and 9 1/4" rear after that?
-jim

Ya, well my truck was built in September of 77, and it's a 78. So I guess the 9.25 was an upgrade. Now, the 9.25's have 3:55 ratio, right?

Not to hijack the post but- I have a '78 PW SE. It is the full time 4wd but there is a light in the dash for the diff lock and also has a selector on the hump. Why is this if the truck is full time 4wd?

By moving the transfer case shifter to Hi-Lock the 4WD dash light will come on. This indicates the transfer case has locked the front and rear differentials to work at the same ratio of tire rotation on all four wheels. Lo-lock does the same, but two times lower in truck speed (like a granny low gear but better).......
If the transfer case shifter is just in "HIGH" position the transfer internal workings determines the ratio of tire rotation on any wheel loosing traction at any point of travel...... When the transfer case in in the High Regular Range when driving this would be called Full Time 4WD on a Dodge truck with a 203 type transfer case.