Hello all,

i have a problem that is easy to explain, but the details make it difficult to convey.

I have a 2008 mustang 4.0L with about 135,000 miles on it. Sometimes in the morning, I cannot get it to shift into reverse or drive. After moving the shifter a few times from park to 1st gear (low), I can get it to catch.

i was reading a few things the past few days, so I can try to explain what it is & isn't. Keep in mind that my assumptions may be wrong. I know enough about cars to fix moderate problems (I have replaced the lower control arms & ball joints and replaced the rack o-rings without looking at a guide, so that kinda gauges my ability),

- The shifter does move, so it isn't the button pin, or the brake light switch.
- I don’t have erratic shifting. Once it is in gear initially, I have no issues the rest of the day and no odd (or hard) shifting while driving, so I don’t think it’s the shift solenoid.
- As you may well know, there is no transmission dipstick, and I don’t have the pump for the fluid to do a level check (whoever thought that was a good idea is a genius.......)
- I'm not sure if it’s a fluid level thing. But if it is, I’m not sure where the fluid would have gone since I have no leaks. Texas heat dried it up? Doesn’t really make sense to me...
- I wasn’t sure if it was a shift cable linkage of some sort. Transmissions are not my specialty.

 

What is the service history on the transmission? "fluid changes" These transmissions are known for servo pin bore wear, causing leakage and improper pressure for the apply piston. Mine took a dump at 117,000. It would hesitate going into reverse, then slam into gear. Got the fluid changed and then all other issues came to light. The PO didn't have any fluid changes. Ford screwed the pooch when they eliminated the dipstick.

 

Yeesh... I hope not. But makes sense. I havnt really done anything to it but routine care. Nothing with the trans because of the dipstick

 

It doesn't sound like a fluid level issue. If it were, it would happen in the forward gears too.

Dipstick or not it's beside the point. The main thing is that Ford decided to put really long recommended intervals for changing the auto trans fluid in these under "normal" driving conditions (100K and more depending on the specific ford model) Problem is, ford as with most other OEM's has not defined what Normal is and most people think they drive "normal". In reallity the vast majority of people should be following the Severe maintenance intervals. Extremes in weather (Snow/Ice and blistering heat like in AZ) along with stop/go driving and city driving is all in the severe category.

Under those conditions, trans fluid should be changed every 30K miles.

Anyways, the fluid level checking procedure is not really hard and is no different than most other OEM's that have done away with dipsticks, not just Ford. Here's a link on how to do it and top it off. the care MUST be level so all four corner must be at the same height.


There is one of two things I believe your problem may be as of right now:
1) The reverse solenoid is sticking. This is common in higher mileage transmissions. There is a check-valve and rubber lined piston inside the reverse servo. Both can become gummed from age and dirt build up from improper fluid maintenance. It's a simple fix but you have to drain the fluid and drop the pan. Then disassemble the reverse servo, clean it out and possibly replace the piston, then put it back together.

2) There is also a thermostatic valve inside the valve body meant help trans fluid heat up faster on startup. The problem is, this valve can restrict fluid flow when the fluid is cold which in turn can cause the tranny to not work smoothly until things warm up a bit and the valve fully opens. Also a simple fix but a bit more involved as you have to not only drain the fluid and drop the pan. You must also remove the solenoid pack and remove the valve body to take the thermostatic valve apart and put the pieces back together in a different order so the valve is stuck in the open position. This prevents the fluid restriction.

If you only do item 1, you will need 5-6 quarts of Mercon V fluid. If you do the solenoid pack and valve body, you will need 7-8.

You don't need the ford tool to refil the tranny, you can use a nipple with a 1/8 NPT thread on one end that would screw into the tranny and a nipple on the other end that fits whatever tube size you use. I use 3/8" ID tubing because it allows the fluid to flow much easier than a smaller size.

 

Thanks for the input. It is happening in drive and reverse. As I said, I have move it back and forth from park to low and. And one will catch and I have no issues the rest of the day :-/

 

i'd consider option 2 first then after check the level. If the thermostatic valve is sticking after it sits overnight, that would cause a pressure issue within the trans which would affect engagement of all gears.