I have a 91 Aerostar 4.0 with a funny tranny. From what I can tell its slipping in the 3rd to 2nd gear down shifts. Usualy it does it accelerating out of turns. I thought it could have been because I was low on ATF when I checked it but when I topped it up it still does it. Also when I get onto the freeway and lay into the gas to get up to speed it hesitates on the 2nd to 3rd shifts. When it goes to shift it feels like I'm engine braking in 2nd and I get thrown forward into my seatbelt but in reality I'm still on the gas and the engine revs up real high like I'm in neutral untill it kicks into gear. Kinda hard for me to explain I guess. Is this something an intermediate band adjustment can fix or am I lookin at an expensive rebuild.

Thanks,
P51man

 

Hi P51man:

Welcome to the FTE forum From what you described, I don't think a band adjustment would cure your problem. It might help if you tell us about the mileage on the transmission. Since you are low on ATF, did you determine where the fluid went? Broken modulator diaphragm?

 

The van just turned 156,000 miles. The previous owner informed me that the tranny was rebuilt about 8 years ago. About a week ago I drove a heavy load (302 engine block, C4 tranny, 2 pairs of cylinder heads ,air compressor, other various items) about 50 miles, and after I unloaded all that and backed out of my driveway, I noticed a nice long trail of fluid leading up to a puddle of tranny fluid. I am assuming that this was also the case when I was low the first time because of a heavy load I had driven somewhere. So once again I topped it up. I would also like to mention how Ford put the the tranny filler tube in the most accessible spot ( sarcasm ). And I say this because somehow in between this and the last time I topped up, I seem to have missplaced my funnel . Anyway, it hasn't leaked since, or at least left and ATF puddles anywhere that I have seen, and I drive about 30 miles to and from work everyday. Of cource not fully loaded like before. The slipping has been an ongoing thing since I've owned it and has been doing it long before the fluid spill. I suppose I'll get under it tomarrow and check to see if there is any fluid in the vacuum line to the modulator. Also, I've been getting about 16-17 MPG. Is this in or around the normal range?

Thanks again,
P51man

 

About 15 minutes ago I pulled to vac line off of the modulator and no ATF fluid. Any other ideas?

Thanks,
P51man

 

The front seal leak usually happens under heavy load and high temperature. I have read about it a lot here on the forum. Practically see one of those every week

About slipping gears, check your fluid level again. Park on a level surface, run your engine, cycle through all the gears holding each position for about 30s. Then check fluid level with the lever in the "P" position. Make sure you check both sides of the dipstick and go with the lower indicator. The wall of the dipstick tube tends to retain fluid right after you fill it. That would fool us into thinking that the level is OK, even though it's low in reality.

 

Well so far the front seal leaking seems to be the only logical diagnosis. I checked the fluid level again and its ok. I want to change the fluid and filter in the tranny and see if maybe that helps stop the slipping but Im not sure exactly how to go about it. I know I could just pull the pan off and change the filter and the 2 or so qts of fluid thats in the bottom but I want to do a full change. I read somewhere that to completly change it you would need to drain the fluid out of the torque converter but I'm not sure how to do that. If anyone has any advice, or a link to a website, or a thread that I might not have found in these forums that would be great. And thats again copper_90680 about the front seal diagnosis.

Thanks,
P51man

 

What I did was to braze a nut (for a 10mm bolt) onto the outside of the oil pan, and used it as a drain. Just drop the pan, change the fluid and filter. Then run it for a few miles, drain through that bolt and fill again. Do that about 3-4 times and your fluid should be plenty clean.

As for brazing the nut on, any muffler shop will do it for 5-10 dollars. Just drill the oil pan and bring it to them.

 

search Aero forum for full 10 qt gentle flush

 

So let me see if Ive got what nighthawk said in another thread about doin a full 10 qt gentle flush.

1) I need to disconnect the tranny cooler lines from the rad.

2) fill a clean bucket with new ATF to suck into the return line

3) have an empty bucket catch the old ATF comin out

4) Run the engine till all 10 qts of new ATF are sucked up

5) reinstall lines and check tranny level, top up if needed

If I'm correct in what I think is ment to be done then I only have 2 questions now:

1) Should I run the tranny thru all the gears while doing this?
2) Should I replace the filter before or after I do this?

Many thanks again,
P51man

 

Yes this is correct.

Not neccessary.

I would replace the filter before. That way you don't waste the new ATF when you drop the pan after replacing all the fluid.