01 F350 7.3 sc 4x4 auto 36,500 miles.

15 degrees this morning, started truck and it lurched forward a little....... weird. Let it warm up, took off and it didn't want to shift into second. That symptom is intermittent. There's also a snapping sound coming from the drivetrain somewhere. Did my infamous diode fail? Do I need a rebuild at 36k? Any thoughts or ideas? Thanks in advance!

 

Mine failed on the origional owner at about that same mileage

 

Your symptoms are those of a failed mechanical diode.

 

That's what I figured...... I just got the truck in june but I tow heavy. I knew it would go sometimes but didn't think at 36k. Anything I should consider adding during the rebuild. Torque converter, valve body, I'm looking for something hd but I don't have Bts/Jw money to spend.

 

Then just buy the ford HD4R100, but make sure thats the one you are getting. 3 year unlimited miles.

Chet

 

So I read in other threads that 4600 rpm under certain circumstances causes the mechanical diode to fail. Why, then, does it matter if a 7.3 has the mechanical diode or not since it never sees 4600 rpm?

 

I dont have a AT in my truck but I've never heard of a 'mechanical diode'. I know a diode does in electronics though.

 

It's a one way clutch, my diode was replaced with a sprag style.

 

That is the exact reasoning that Ford used when they pulled the mechanical diode out of the gas trucks at the start of the 2001 model year but left it in the diesels.

The truth is that at 4600 RPM it is possible to destroy the mechanical diode in one shift, if the driver knows how to do it. At lower RPM like the diesel turns it takes longer, but they get there, too.

Mechanical Diode is a brand name for a type of one way clutch.

 

So, horsey, what happened?

 

Ahhh, gotcha. Thanks.

 

I brought my truck to a local reputable transmission shop where it was rebuilt with a list of improved parts and upgrades to make the tranny more HD. Billet triple disc tc, valve body improvements for better shifts and increased line pressure for less slip, better clutches, I forget the rest. It was done within a week and cost $3,150. It is disheartening when it happens, especially since I bought the Ford 7.3 for it's reliability - add in a bunch of other stuff I'd rather not have to deal with; hutch, harpoon, 50 cent mod, vc harness chafe, cps failure, od steering column wire, ect, this truck may come up for sale sooner than I expected.

 

Not trying to hijack a thread, but my 01 started acting up today, almost like a bad u joint, which its not. Contemplating buying an upgraded HD rebuilt, and installing it myself. How can I flush my tranny cooler before putting in the new tranny?

 

Yes, I hear ya! Pretty much a love/hate relationship here, but it tows our trailer pretty well. The only reason I have it is to tow with. Hard to say if others would be better, and we do have the benefit of learning from others.
If not for FTE it would have gone buy buy a long time ago.

 

Thats a bummer. I dont have a 01 so I dont have the diode issue, but for what its worth, I have never done any of the other things you mentioned on my 02, knock on wood, up to 150k.