I have a 1994 F350 with 87000 original miles. I bought this truck 1.5 years ago and the transmission has been nothing but problematic. Very soon after i purchased the truck the transmission went after pulling a trailer for about 40 miles. I had the ****** rebuilt (Unfortunetly at AAMCO) with heavy duty parts, upgrade sun gear, torque converter the works ($2600) and things seemed to be ok, however i didn't pull the trailer much (had another truck). this all occurred at around 79000 miles. I moved from VA to CA and towed my 69 Bronco with this truck cross country. About Nebraska the OD light started blinking intermittantly but the truck did not seem to run any differently. When I got to Seattle (left truck at buddies house for a while) i had the local AAMCO shop diagnose this issue. They say they found a wear groove on one of the valves in the valve body and the truck computer was bad. So another $550 later the truck seemed to run fine again. When my buddy hooked my Bronco up to tow it to CA for me he made it a whopping 90 miles before the truck would not shift into OD. By the time he made it to yet a third AAMCO shop the truck would not go into reverse. 2 weeks later the shop told us they could not duplicate the problem and had towed a car around for a few days??? So i had them change the filter and fluid. My buddy had already towed my Bronco with his "Dodge" so he brought my truck without a load and the truck ran like a charm. Last weekend, i took my truck to the mountains, about 120 miles away, loaded the bed with wood and came home without even a hickup, it ran beautifully. Then i get in it this morning drive 20 minutes to the airport with no load and after i take the exit the truck won't shift into OD and the OD light is blinking. What is going on with this thing? My instrument cluster is jacked in the truck and the TACH is completely jacked. I replaced the tach sensor and had this problem diagnosed by Ford. My question is is there a feedback loop from the tach to the tranny that could be causing this, if so why doesn't it happen all the time? Could it be a Speed sensor causing the issue? Any other ideas are welcome!

 

oh man what a time of it.sorry to hear about your misfortune.
the first thing you need is a code reader.
example;
Actron/OBD I code scanner for Ford 1984-1995 (CP9015) | Code Reader | AutoZone.com

your first failure,sounds like a plugged up cooler line issue.within 40 miles,she must not of been able to transfer oil through her vanes to cool down.no doubt after failure,when you went to check the trans level,you then saw and smelled very black fluid.
one of the most important gauges to have is a trans temp gauge.it could have saved the whole issue right from the start and you'd likely have the original trans still.

"My instrument cluster is jacked in the truck and the TACH is completely jacked"
thats not good.can you provide more details?

 

Thanks for responding.

The tachometer is not accurate at all. At idle i think it is some what ok but if you rev the engine, it spins up like a motorcycle or sports car. will go all the way over and peg the tach. Sometimes it bounces around 2000 rpms for no reason. When im on the highway at ~65mph the tach is reading 4000. One of my fuel gauges is bad and the ford dealer said it was the cluster. pretty sure the cluster is no good, in fact i ordered a new one this morning after my post.