Title pretty much says it all but here's the long of it...

Bought this car about a month ago. 103K miles from some older guy. I was recently rear ended and I've been looking for a beater to get me by for a little bit. Besides needing brakes and the suspension squeaking like crazy, it drove great for 15 minutes... So I bought it for 3500 bucks (had some body damage). It wasn't until I got home and cleaned it I found some receipts in the car... One for some transmission fluid... (look of concern in my soul emoji)...

Driving around the car will go into a limp mode (seems to default to 3rd gear when in Drive). Usually seems to happen when shifting around 5th gear. 4-5 or 6-5 I think. Everything works otherwise and I'm able to pull over, restart the car, and continue on my way. Sometimes it comes back relatively soon, within a day... Sometimes it goes a few days.

I actually just got back from a 1500+ mile road trip and it did it once right at the start, and once right when I got home. It was probably stupid to attempt the drive... But other than the fault causing me to pull over twice, the car did fine... Mind you this was during 80-115F weather doing 70-90 MPH almost the entire time. (Side note... 28 MPG... Impressive! A/C in this car... Not so impressive. lol)

Yesterday, I got home from work and it happened again I think when I put it in Reverse, though I don't know for sure. Might have happened in D going down my street. When I backed into my driveway, I had smoking off the driver side of the engine, but that was probably due to some oil I spilled topping the engine off the previous day (used half a quart on my trip). I only note the smoke incase there are transmission cooler lines or something I don't know about on that side.

I'm using a cheapo Bluetooth OBD2 reader with an app (Torque Pro) on my phone. I've had good results with it previously on other cars. Codes are...
P0735 (Gear 5 Incorrect Ratio)
P1111
P1000

Things I've done to try and correct the issue.
Changed battery to a new Interstate from Costco (old one was 4 years old)
Cleaned battery terminals and grounds in trunk and behind headlights

My next step is to get under the car and try to check fluid in the trans. I'm aware there is a specific way to properly do this. I may drop the pan just to see if there's anything obvious... I know to use Mercon SP.

If anyone has some solid advice on what I've described I'd appreciate the input... I'm not really in the mood to completely master another vehicle and rebuild a transmission. I'm hoping just maybe I'll get lucky and the fix is relatively simple/cheap...

 

Figure I'll pick this up if I drop the pan... Too bad its 200 bucks just to open the transmission up.

https://www.oreillyauto.com/detail/c...n+filter&pos=1

https://www.oreillyauto.com/detail/c...id/mot0/xt6qsp

 

One small note; make SURE you (are able to) loosen the fill port before opening drain port and/or dropping pan. If the transmission has never before been serviced, the fill port can require a lot of torque to break free. Plus, its going to make refill easier if you have already loosened fill port on side of trans once you get covered in slimy greasy trans fluid .

Now, for the part many, many people will have differing opinion on...I always add two of these to increase the additive package in the trans fluid. It's just opinion, but I can really tell difference on the 2004 X350.

https://www.oreillyauto.com/detail/c...additive&pos=0

 

*** Having issue finding MERCON SP ***
Will see what I can find Monday, but other cost effective suggestions would be appreciated.

Currently looking at Valvoline MaxLife ATF... But I'm reading some people suggest it... And some don't.

*** Update Again ***

Now looking at getting this instead... will be about 200 bucks but comes with 6 quarts of what I guess is the ideal fluid to run and bits to do some I guess common fixes/service items on the ZF

Life guard fluid 6 (6 Liter) - ZF PARTS - S671090255
Rein TSK0018 Transmission Service Kit

If anyone has a legitimate opinion on the Valvoline MAXLIFE ATF in the ZF 6HP26... I'd love to hear it.

 

Could be as simple as low oil. My experience was getting bad shifting, getting stuck in 4th and not shifting up or down until revs dropped and all sorts of lurching and horribleness... Bought new pan, oil etc, even serviced the valve body seals (important to do) and discovered a relatively new pan. Someone had "tried" to do a service but left the box short by a couple of litres of oil.... As far as oil I used, I went with the ZF but there's plenty of literature around and there are equivalents that work just as well and don't cost as much.

Also, don't expect miracles from the off. Some issued took a couple of weeks of relearning for the box to smooth out and start functioning properly.

 

As for fluid, this is my go-to: https://www.blauparts.com/ravenol-at...id-6hp-4l.html

Nice thing about Ravenol is it comes in a 20 liter pack so you can do a drain - pan replace - fill - drain - fill.

Very good vendor and high quality kit: https://www.thectsc.com/products/oil...ce-186-61.html

Valvoline Maxlife; now please, don't anybody have a hissy fit, but my opinion its risky cause no one oil can have the appropriate material specifications AND additive pack for so many different transmissions: I think Valvoline over-reaches on the specs trying to make a oil that makes it "easy" for big-box stores to stock one item. I'd stick to ones that focus on the ZF 6 speed. That said, I know many have used Maxlife and are pleased.

 

@NEFF While you have pan down you may consider replace some rubber seals. This will require removing mechatronics plate, and if you do that; then it is advisable to replace mechatronics sleeve.
This is example from e-bay, but I would use more reputable supplier.
https://www.ebay.com/itm/38701297995...yABEgLYkfD_BwE

There are number of video's on YouTube showing how to do it. Sorry do not have time to search to find a relevant.
This one is good, example: same transmission only on RR: It would be a little more adder $$ in parts, but if you will want to return to this later again it will cost you refill in transmission fluid..

If you decide to replace seals, PAY ATTENTION to part numbers! There are two transmissions that have similar components, BUT they are not interchangeable!

 

Big Koshka make a VERY good point; the newer seals have an improved o-ring

Here is a link to the definitive change procedure video, from ZF themselves;

 

Zf 6hp26 oilchange kit pan with filter magnets screws 7 liters of zf6lifeguard oil and electrical connector seal

Bridge seal mechatronis sleeves and electrical connector seal

I would just drive for ten min, raise car levelled. Open up filler hole (left side above pan. ) hex. If it dribbles oil at 40-50 degrees celsius the oil level is fine.
if it is wrong or old and smelly oil you could, just to see if improvement is possible, drain the oil over the plastic screw in the plastic pan ( about 6 liters then) close and refill with new correct oil , go trough J gate in all positions then start checking temp oil again. Fill till it dribbles abit than close
try the car.

 

Check with a Ford dealer's parts counter--I've always had good luck going that route. Otherwise, I've been able to get Mercon SP at Advance Auto Parts.

Paul