I am new here and can't figure out this forum. If I am in the wrong place please tell me how to use this thing. I have a 99 F-250 LD that has a 4.6 auto. It acts like the tranny is slipping. It creeps until you get high RPM then bangs into gear. If you let off the gas it does it again. If you hold your foot on the brake and the gas to keep the tranny loaded it stays in gear. I have older tranny experience but nothing this new. Any help appreciated.

 

Your in the correct forum for your truck, but you might also post your question in the forum that deals with transmission also.

Anyway what color is the transmission fluid, how long ago was it changed, and is the fluid level correct?

 

The guy I bought it from said he had the tranny flushed and filled. It is at the full mark but it looks more like clean engine oil than tranny fluid. I am used to red this is clearish tan. Also once the tranny engages it will flat smoke the tires in a 1st and 2nd gear power brake. Definitley not burnt up.

 

It should definenity be red, I would hate to think somebody put engine oil in your tranny. What I would do is change out all the current fluid and put in new Mercon 5.

 

When you do that, be sure to crank the engine a couple of times so that it pumps the oil out of the torque converter.

 

I will definitley give that a shot. Any opinions on the possibility of the mechanical diode/sprag being the culprit? Seems strange to me that it works so well in reverse. I haven't had one of these trannies apart yet so I am not sure where that md/sprag is or what gears it affects.

 

I tried tranny fluid and sea foam. Seemed to make no noticeable difference. A transmission specialist told me it was clutches. I pulled the tranny, disassembled it and guess what...clutches all look good. Bands all look good. Everything mechanical seems fine. Is there something to check in the valve body or should I just give up and get a salvage tranny?

 

What a rookie mistake. I overlooked one set of cluthes. Turned out to be the forward cluthes. They still had friction material left but very little. The tolerance on the ***. clutch pack was way off. Found it when I was reassembling the trans. for storage. Oh well. Lesson learned.

 

Glad you figured it out before putting it all back together.

How many miles were on the unit?

 

240,000. It was an oil field truck. I got it for little a nothin. Doesn't smoke. Everything works. Just had trans. trouble. If you don't look at the odometer you'd never know it had 240,000. I think that says something for Fords 4.6. I here it dogged alot. I have had 2 and I think they are good engines. Apparently 4r70w ain't a bad trans. either if it goes 240,000

 

Oil field trucks do not have easy lives.

That is saying something about the engine and the tranny.