I have a 1996 single cab 4x4, 302 motor, and 4r70w transmission. I recently rebuilt the motor (rings, bearings, seals), it runs, revs up well in park, and idles great, but I cannot accelerate uphill, or much at all, so I checked compression and it read good. However, while I was rebuilding the motor the trans pan was left finger tight by previous owner, so all the fluid leaked out while it sat in the driveway. I went ahead and changed the gasket and added fluid per the dipstick. Here comes the issue, when driving, it has a had time accelerating, it feels like when I hit the gas very little is happening, and it has an incredibly hard time going up hill. When I floor it there is little response, sometimes it just wont rev up, and sometimes it will misfire until I let off, it will also not downshift based on throttle position. When stopped, shifting from park into reverse or drive, it stalls, but only sometimes, other times it will go into gear with no issues and idle fine. I am concerned that I may have an ecu issue, torque converter issue, or when I changed out the fluid it messed up the clutch pack, although it doesn't feel like slipping. When I bought the truck it drove home with minimal issues outside of a terrible misfire, and nothing relating to my current issue that I think is happening with the transmission. Also since the rebuild the speedometer has stopped working.

I really have no idea where to start, I know very little about transmission, although I guess I am going to end up learning a lot now haha.

 

Given your comments about not revving up, misfire, etc., suggest to take another look at the engine - start with the simpler stuff like timing and fuel pressure checks and checking the computer codes and work from there.

My opinion is to get the engine right first, and then chase after possible tranny or other issues.

 

What he said
Check the timing with the spout plug out
Should be near your ignition control module by the drivers side hood hinge
Check for any codes and check the fuel pressure

 

So, it has absolutely nothing to do with the transmission, and everything to do with ignition timing, the sound is backfire through the intake. I tried to time it the right way, timing light and all, had to buy a new sensor, one that has the timing pointer for the harmonic balancer on it, old owner lost it I imagine. However the mark on the harmonic balancer is pointing straight down at tdc, not sure why, my plan is to find tdc and put a timing tape on it, so I can time it properly. Currently I've just been doing it by ear. Took the little plug thing out to set the ignition timing, and tried to get it to run good. Engine shakes like hell, has fluctuating idle, and backfires out of the intake. It threw an icm code, so I replaced that with the correct Ford motorcraft icm, the black one, and the icm code went away, still runs like crap . I threw a throttle position sensor code, but only once, didn't come back after I cleared it. I also made sure my plug wires weren't cross firing, and purchased new wires and plugs. It nearly constantly backfires under load at I guess 2-3k rpm, it doesn't have a tach. Could it be the throttle position sensor, the pip thing inside of the distributor, an ecm issue, or something else? It isn't throwing any codes anymore other than a temp sensor code (not sure why) and a p1000 code, for not enough running data collected.

 

Hold up there!

Memory has faded - so hopefully other users will jump in, help out and correct to get things steered in the right direction - but recalling the timing mark being a pointer attached to the block at about the 10 o'clock position overhanging the balancer as viewed from the front, and various degree mark scribes were on the harmonic balancer itself.

Not sure what your described mark is on the balancer itself. These scribe marks get covered over with dirt and road film becoming near impossible to readily see, sometimes a chore to find even looking up close, recommend cleaning that area up with a wire brush and then putting a white or visible line using a soapstone, paint pen or the like at the 10 BTDC scribe to line up with the pointer when timing. Essentially when the #1 (passenger side front) cylinder is physically at TDC, the TDC scribe mark on the balancer should line up with this fixed pointer, all in the 10 o'clock or so position.

Opinions will vary, but your description sounds like the timing is way off. Whatever the cause, suggest to figure this timing out before changing any more parts.

 

Borrow a timing light from a parts store
Timing by ear will not work well at all
Even the vacuum gauge method has faults
Use a light, double and triple check the firing order