So not ure where to start with this. When in gear at @45mph or more it's like a rumble strip is under my foot and doesn't want to take the power it is givin. I noticed that when leaving from a stop its doing a similar but less violent thing. Trans fluid is red, didn't notice any metallic flake. The truck says 76,000 but when I bought it car fax had a red flag regarding the turning back of the odometer so for all I know it could have 200k on it. I'm the type that likes to fix things herself( with the help of others who know what they are doing). I used to race cars and have worked on these things before, but a drag cars' Hughes transmission is totally different than what this old girl has.

I'm debating on taking it for a diagnosis for free but the places near me are...well you know.

 

Not sure this will be helpful but...............

If it has limited slip differential make sure the fluid level is proper OR change that fluid and re-install with new lube including the friction modifier required for that rear gear.

If not LSD then could be an issue with the ring and pinion gear not meshing properly, have to remove the rear cover to see what's going on.

This is all assuming you've checked the drive shaft u-joints and they're in good condition. Also that you're not showing any DTC's for the transmission.

 

Mine felt the same way and ended up being a misfire on 2 cylinders. I was certain it was the trans/rear end though as I have had problems with both that felt nearly identical. Just a thought.

Scott

 

The free diagnostics are usually worth every penny.

I can give you a free diagnostic from here that will most likely be correct. You have a misfire on at least one cylinder.

I recommend all new coils and spark plugs. You can try to isolate which cylinders have the problem and just fix those, but chances are that the ones that don't have a problem now will have one soon.

 

OP doesn't mention if MIL is lit up----would be helpful info to further offer free how-to-fixit advice.

 

Most E350s aren't OBD-II compliant from that year, and a misfire code won't illuminate the check engine light. I had a current misfire code on my old Excursion that never illuminated the light.

It should be scanned regardless. How does it idle? While it's running you can usually hear a misfire from the tailpipe

 

This was the case with mine as well. I rarely drive on the highway and never actually completely the drive cycle to throw a code (no MIL for these as mentioned above). After a quick jaunt on the freeway I was able to pull the misfire codes for 2 cylinders. Turns out there was a fair amount of corrosion on the electrode (coil side). I cleaned it up, greased it and reinstalled it and have had no issues for quite a while. The cost of this repair was $0 and shows that throwing money and random parts at something to fix it isn't the only option.

Scott