When cruising down the highway in OD with the converter locked-up, if I let off the gas, I get engine braking. If I downshift from OD to "drive", the eng goes to idle and I get no eng braking at all. Same thing happens if I downshift to 2nd or 1st gear. From the searches I've done, it sounds like the overrun clutch is fried.
When I checked the tranny fluid level it was abt a pint low, so I filled it to the top of the hash marks on the dipstick. I went for a test drive accellerating with shifter in second gear then letting off. I got good engine braking and thought that I "fixed" it. However a couple more miles down the road, I downshifted from OD to drive, then to second gear at abt 45 mph and I got no eng braking. I still have eng braking in OD with the converter locked.
Other than having no eng braking, the tranny seems to work fine.

If the overrun clutch is fried, why do I still get eng braking in OD with the converter locked? Why would it start working again then stop working again?
Do I risk further damage if I continue to drive the car as is? Thx!!

 

check the shifter linkage for proper adjustment, then start checking inside for things like missing checkball on inputshaft, burned band, stuck valves,dammaged plate gaskets, check servo for broken pin, any other obvious dammage.

 

Thx for the reply!
Other than the shifter linkage, is there anything I can check before pulling the tranny out? It's only got ~30K miles on it since rebuild.
I've never been into an automatic tranny (other than removing a valve body), so I don't really know what I'm looking for. Can you recommend a website with good pics to help identify the possible causes?

 

Got the tranny disassembled today. The overrun clutches were wasted.

 

This is always a overrun clutch assembly problem when there is a "no engine braking" action when the shift lever is in the "D" position. It can be the clutches, overrun sprag, or a broken overrun hub. This happens occasionally. How did everything else look inside?

 

Thx for the reply Probuilt.

The input shaft pulled out of the input drum during the tear-down. From what I understand, that's not good.

Also noticed the end of the input shaft was chewed-up where the 3 check ***** are (the splines looked fine). The front end of the output shaft looked fine. Inside the input drum, where the input and output shafts meet, the alum was chewed up a little. Wondering if this damage was causing a low oil press condition contributing to the overrun clutch failure??

A couple of the metal overrun plates came out in pieces.
All the other clutch plates looked pretty good.

The clutch spring assy near the tailshaft was found cocked (all the springs were laying over at a 45 deg angle). I was able to turn the assy so the springs were upright again and we were able to compress them and remove that last snap-ring. Once the clutch springs were out, I noticed they lean over abt 10 degs or so. Not sure if I should try and re-use them or not.

Didn't see any other damage.

I'm running a 383-TPI and want to build this tranny so it can handle 500 ft-lbs of torque. Since it's looking like I need a new input drum anyway, I'm looking around to see if there are any upgrade drums available, hopefully in a kit with all the clutches.

 

Also noticed the end of the input shaft was chewed-up where the 3 check ***** are This is normal.

The front end of the output shaft looked fine. Inside the input drum, where the input and output shafts meet, the alum was chewed up a little. Replace it!

Wondering if this damage was causing a low oil press condition contributing to the overrun clutch failure?? NO!!!

The clutch spring assy near the tailshaft was found cocked (all the springs were laying over at a 45 deg angle). I was able to turn the assy so the springs were upright again and we were able to compress them and remove that last snap-ring. Once the clutch springs were out, I noticed they lean over abt 10 degs or so. Not sure if I should try and re-use them or not. Replace it!

I'm looking around to see if there are any upgrade drums available? Call me on this.......