AOD gear slip

[mfmagicmike]

Hi everyone,

It seems I am having some trouble again with my 89 Crown Vic (5.0 AOD at least 240 000 miles, overall in excellent condition)!

I just came home from a 250 miles x 2 trip, and here is what happened both ways:
First 180 miles, everything was going fine (outside temp. approx 82°F, average speed 65 to 75 miles). Then acceleration became jerky, as if the fourth gear was slipping. I stopped, checked the oil level (OK), even put in some more oil, and continued my journey. Yet transmission remained jerky for about 100 miles. The last part of the trip (off the highway), I drove slower (approx 45 to 55 mph), and after half an hour, the transmission worked normally again.
After a few hours of cooling down, the car worked perfectly (that was yesterday).
Today, trip home, first 180 miles, everything ok, then the slipping started again, real bad (almost totally lost acceleration). Having no choice other than trying to reach home, I continued my journey and luckily the car didn´t break down. The slipping went on for approx 100 miles. Again, after leaving the highway, slipping stopped after 20 minutes of slower driving. (outside temp approx 70°F, rainy).

Could this failure be due to oil overheating ?
How bad is this symptom, does it mean my transmission is going to break down completely soon?
What do I have to do to fix it?

Thanks for Your expert advices and help!

[Southern_Pride]

Sounds like the od band is near shot. After cooling they do grab again. How do the rest of the gears feel when shifting? The trans could very well last a long time without od.

[Pirate]

[mfmagicmike]

After stopping, 1st, 2nd and 3rd work perfectly (maybe a little slip when hot in the 3rd when kicking down), with OD. The fourth when hot & slipping even slips when switching from OD to D. When cold all gears work normally (smooth +++).

Off course, TV cable & grommet are OK and set to factory specification, oil & filter have been serviced less than 1 year ago.

Are these OD bands serviceable/replacable (DIY job?)?

[Pirate]

After stopping, 1st, 2nd and 3rd work perfectly (maybe a little slip when hot in the 3rd when kicking down), with OD. The fourth when hot & slipping even slips when switching from OD to D. When cold all gears work normally (smooth +++).

Off course, TV cable & grommet are OK and set to factory specification, oil & filter have been serviced less than 1 year ago.

Are these OD bands serviceable/replacable (DIY job?)?

It sounds like both the O/D band and the direct clutch (required for both 3rd and O/D operation) are going a little south.

So far as a DIY operation....well....try to find an exploded view of the transmission first before you get too carried away, as it's a bit of fun getting to the direct clutch.

One other common mistake of the DIY builder is that hardly anyone stops to think where the clutch material went after it was burned off of the clutches in question; usually it ends up going straight to the valve body, even though there is a filter in the bottom that's supposed to prevent that sort of thing. I've pulled several apart to find valve body passages half-choked off with burned clutch material, which wreaks havoc with the valves due to the AOD having a crappy VB design, in which steel pistons move back and forth in an aluminum body, which eventually causes galling in the valve bores, and making it impossible to get the tranny to shift right.

I'd just start looking for a replacement out of a 1989-1993 Thunderbird Super Coupe, or a 1989-1991 police car....maybe even a 351W-powered 1/2-ton van. I have a rebuilt 1991 SC tranny that I bought for $120, just because the guy couldn't sell it, and simply wanted it out of his shop....so there are deals out there.

[mfmagicmike]

Off course, replacing the whole transmission seems to be the logic thing to do, especially considering the mileage. I was just hoping a simple (and cheap) replacement could do it. Off course, I am not a transmission expert, and it seems to be a tough job - either swap and/or repair, unfortunately for me.

[gadget73]

If the engine is running hot, then it might contribute. I'd probably suggest adding a trans cooler, some more TV pressure, and prayer. I'd also verify the engine is not running hot, since the factory stuff only tells you when its over 250, which is way too damn hot.

[mfmagicmike]

If the engine is running hot, then it might contribute. I'd probably suggest adding a trans cooler, some more TV pressure, and prayer. I'd also verify the engine is not running hot, since the factory stuff only tells you when its over 250, which is way too damn hot.

The idea of engine overheating is good. A few months ago, I threw in a new water pump, thermostat and coolant hoses. Maybe something is not working correctly (chinese thermostat?). And since I didn't travel that far since the swap...
I also noticed that the new hoses, especially the one passing over the right valve cover was covered with blue dust (which didn't happen with the old ones), and which may suggest excessive heat.

Any idea how I could check the engine running temperature ?

[gadget73]

Install a temperature gauge, or get one of those infared heat gun things that you can point at the motor to see whats going on.

[mfmagicmike]

Thanks for the help.

After thinking it over, I might have installed a thermostat with a high opening temperature. What I am sure of is that the box it came in didn't mention anything about opening t°.

What opening temperature would You recommend for the 302 V8 engine? 160°, 180° or 195°F?

[gadget73]

195 is stock, and should work fine if the rest of the cooling system is in good shape.

[mfmagicmike]

Thanks for the tip. Would a 160° thermostat in summer and 195° thermostat in winter be a good compromise (old engine and old transmission)?

[mfmagicmike]

I just ordered an auxiliary transmission cooling system. Does any one know how and where to install it?

[mfmagicmike]

One other common mistake of the DIY builder is that hardly anyone stops to think where the clutch material went after it was burned off of the clutches in question; usually it ends up going straight to the valve body, even though there is a filter in the bottom that's supposed to prevent that sort of thing. I've pulled several apart to find valve body passages half-choked off with burned clutch material, which wreaks havoc with the valves due to the AOD having a crappy VB design, in which steel pistons move back and forth in an aluminum body, which eventually causes galling in the valve bores, and making it impossible to get the tranny to shift right.

Any chance to clean these valves while changing filter and tranny oil?

[gadget73]

Thanks for the tip. Would a 160° thermostat in summer and 195° thermostat in winter be a good compromise (old engine and old transmission)?

Not really. The ECM wants at least a 180, but you'll get better performance and less wear from a 195. The other thing is, the thermostat only sets the minimum engine operating temperature. If you have a clogged up cooling system, you'll overheat with a 160 the same as you will with a 195, it just might take a little longer to get there.

Trans cooler plumbs in in-series with the cooler in the radiator. Usually you mount the cooler in front of the radiator and AC condensor, and use some rubber line to connect it all up. These are the factory coolers on my car, you can see how the plubming and mounting is done

Upper cooler is the trans cooler. The thing that looks like a loop of steel line is the power steering cooler. You do not need one of those.






The upper metal line is unmolested. The lower one is basically cut a few inches out from the radiator, and the external is plumbed in between it. I have factory cooler lines and plumbing so mine is slightly different looking than yours will end up, but functionally its no different.