Some background: My 2007 F150 2wd 4.6 139k had the fatal "revs and bangs leaving from a stop" problem. I tore it apart and found the center support ring broken and the direct drive welded to the sun gear stub shaft. No burnt fluid or bad clutches.

Phase 1: Ordered kit with Alto frictions and band, new/reman converter and replaced the wear parts. Flushed lines, pre-filled converter w/2qts, and waited for the rain to stop. Did the J-mod just for S&Giggles.

Phase 2: reinstalled, refilled with fluid, allowed it to get to operating temp to melt the assembly lube, then ran through the gears and while it was in the air ran it in forward and reverse...all good. Off jack stands, topped up fluid 13.5qts total used, and took it on a road test. Shifted fine at first then lazy with flair into OD. After several stops, free revved instead of shifting into OD.

Phase 3: Countless hours researching specifics, ordered Sonnax OD kit and installed. Removed, cleaned and thoroughly inspected valve body. No debris found, no sticking valves. Road test went perfect for several miles then no OD. Has excellent engagement during deceleration test and drives perfect 1-2-3. No codes present. Tested ohms on solenoids and all are good. Tested harness and had continuity.

Any ideas on a culprit? I would rather not pull it out again and wont be investing in parts to try and diagnose it. Local tranny shop said it had a burnt band and needed a rebuild(yeah, even though it is new).

All help is appreciated.

 

When you put it in manual 2nd do you get engine braking when you let off the gas or do the engine rpms drop like it would in neutral and the truck more coast than slow down?

D

 

Good morning Darrin! Thanks for replying.

I have a firm, near instantaneous engine braking when dropping from "D" to "2" above 47mph (that is the speed that I test above to be consistent) and it works every time. I did have engine braking after the original refresh and again after installing the OD servo kit.

The best way to describe what it is doing would be to say it is "hunting" for OD. It goes into OD then slowly slips out, then the rpms will drop and then surge (neutral) and repeats. If I floor it when it neutrals OD it will rev high, downshift and go like stink. Well as fast as a 4.6 can go....

 

I've almost got to think this is in the valve body then.

Could definitely be wrong though.

D

 

I was careful on the first go-round with the valve body and downright OCD about it the second time. its a mystery

 

Darrin,
Thank you for your time. What are your thoughts on these points:

1) I used a generic dex III with Lubegard M-V additive. I new I would be doing a flush and fill very soon. Can the fluid cause the problem?

2) What if I pinched one of the piston seals? Could a pressure loss be the culprit?

3) Should I roll the dice on a reman valve body and new solenoids or would that still be chasing the problem with parts?

 

Why would you put Dexron fluid in a transmission that requires Mercon V?

 

1) As alluded to already, don't do that. I don't care who says what, another fluid that is not the same as Mercon V does not somehow become Mercon V with an additive. It's not the same. Use Mercon V.

2) Doubt it's a seal. Doesn't make sense with the described symptoms.

3) I am leaning very strongly toward the valve body. If you go this route you might look at a modified valve body. You get something better for the same or less than what most pay for a simple reman.

Let me know if I can help in any way

D

 

Supposedly, the lubegard M-V additive creates a chemically similar fluid that contains the correct friction modifiers, albeit non-synthetic. Again, I knew I would be doing a flush and fill very soon and this fluid was sacrificial.

 

I understand about the fluid and will correct asap.
I will contact you directly during the week.
ps. Drove it last night and had all gears including OD until I stopped for gas. As soon as I got back up to speed it...nothing. LoL, it was just teasing me!
Thanks again Darrin.

 

I forgot to come back and post what the problem was and the eventual fix.

Soooo.... I gave up and pulled the transmission back out and disassembled it expecting to find something, anything. I didn't find anything. After some contemplation and monetary computation, I took the basket full of parts to a local shop. The builder found the replacement parts that I purchased used from the local rebuilder supplier were old, previous generation parts. They worked but were not exactly right.
And then he gave me the news, I had cut and rolled the teflon seals on the output shaft when I installed them. It maintained enough fluid pressure to operate until it was in overdrive and then dumped the fluid due to that massive internal leak. Oops.

The builder found the gear set was a bit sloppy so we installed a new one while it was apart.

In all, he replaced the direct drum, piston, clutches & steels, the sun gear, gear set, and the bearing. The teflon seals were replaced too, of course!

The old gas sucking pig is back up and running. Thanks for everyone who offered help especially Darrin. Diagnostics over the web/phone are a magician's trick at best.