I have a 2001 Excursion 4x4 with a 4r100 transmission. I have noticed that sometimes the 1-2 shift is very smooth and other times it is MUCH harsher. The transmission fluid and filter was just changed with 22 quarts of Mercon V (Marks method as posted). It did this before the fluid change and has not changed after. It seems to be very throttle and rpm dependent. It seems to do it more when it is a very light throttle as accelerating. If I give it more gas like towing or pulling into traffic, it seems MUCH smoother. It does not seem to make a difference weather the transmission is hot or cold? All of the other gear changes up and down feel very smooth. The down shift from 2-1 is also very smooth.

Any Ideas? Or more information needed?

Thanks

 

Mine does this sometimes, but seemingly random. I will watch the thread.

 

It seems to be worse if I am letting up on the gas at the time of the shift.

 

I wonder if you may have the dreaded mechanical diode? I've heard some got into the gassers.

 

Mines got it. Been like that forever. Oasis says it was there on new purchase.

 

P-nut, does it shift like I described?

 

Your '99 has a mechanical diode? That's interesting since Ford didn't put it in any truck until 2001.

 

I don't think that mine does. The tag says "REMANUFACTURED" But i am not sure how to decode the numbers. I assume that with this tag, it was remanufactured by ford?

This is what is on the Tag:

(Barcode)
6278-18
(Barcode)
R2471418
(Barcode)
1C3Z7000DCRM

 

Erratic shifts can sometimes be attributed to a "sticky" line pressure modulator valve in the accumulator.

Read this page from Sonnax, as they've developed this valve just because of that problem:
http://www.sonnax.com/system/announcement/96948-05K.pdf

For most purposes, the .427" valve is the one you want.

They also sell some shift-improvement springs that I'd recommend highly for tighter shifts.

Pop

 

I have documents that prove my 4r100 has had this diode diagnosed and replaced under warranty and that the problem still exists. It has 177,000 miles on it now, that was done at 8,538. I'm still on my original transmission.

 

p-nut,

I think it's time for you to scan those documents that are your proof, and send them along for us to examine.

Better read Mark's sig line and recognize he KNOWS HIS STUFF when it comes to these transmissions.

No diodes in the 1999's.

Either you are mistaken, or some dummkopf didn't have a clue what he was writing when he provided you with "documentation".

Sorry.

Pop

 

What Pop and Mark said ^^^

 

Ford didn't install a mechanical diode in any 4R100 before July, 2000. Maybe your trans went through a time warp and was built after July, 2000, and then installed new in your '99.

 

Whatever. I know oil changers who "know thier stuff".

Who would you trust? An oasis report/reciept of services rendered or some dude who claims to be a former "transmission engineer" on the internet. Sorry, but this isn't worth my time digging through years of reciepts to prove a senseless point.... Sure, for times sake, it doesn't have a diode and I'm just a big liar or whatever you want to hear.

Thanks.....

 

I Yie Yie.....