73 Scout II with 440 chrysler. Po was shredding the tires and blew the spider gears out of the rear end.
After replacing the rear axle and getting the engine running I found I had only reverse.
I checked the fluid with trans in neutral and added two qts. Put shifter through all positions but still no forward, only reverse.
Did the po blow this trans or maybe broke something simple to replace (yeah right)?
While there are a few other areas that could affect the symptom of "no drive in forward", I'd suspect that the overrunning clutch has spun in the case bore. And that is based upon the huge amount of abuse it would take to wipe the differential guts!
The overrunning clutch is more commonly referred to as the "sprag". It is the last item to come out of the case when performing an overhaul and the first item to be loaded into the case when rebuilding. Normally, nothing is required to be done in that area other than a cleaning and inspection of the springs, rollers, case, thrust surface, etc. Then the sprag is simply re-assembled.
A "blown" sprag means the outer race has spun in the case, it's retained by a fine serrated outer circumference, a set screw, and multiple stakings at the point of manufacture. Many years ago, the aftermarket developed the "bolt-in" sprag as a simple repair for a blown sprag and as a means to salvage an otherwise non-repairable case. Typical cost for these repair units is in the $125 range, they are all the same in actual design/installation/operation, one is no better than the other.
However,...if the bottom of the sprag bore shows signs that it has been heavily damaged by this failure, then the case will have to be machined and a specially-fabricated torrington-type thrust bearing installed in order to be able to use the case with a bolt-in sprag.
It's always possible that one or both of the clutches have toasted also, but no matter, the transmission must be disassembled in order to diagnose/repair this condition.
You can screw around with the oil change, band adjustment, valve body cleaning, etc, but it's far more likely the sprag is blown.
This is not a "normal" 727 failure, a blown sprag, like a broken low/reverse (rear) band, is caused by major abuse such as slamming the trans back and forth between first and reverse with a high idle speed (or wot).
This pic shows a "bolt-in" sprag outer race, with hardware before installation. The difference in that item and an oem race is...the four small threaded holes in the perimeter and in some cases, the race has the perimeter serrations cut a bit larger in od and depth to provide increased "bite" when pressed into the case.
