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Transmission Troubleshoot

RiverVegas

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June 2, 2016
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City, State
Las Vegas, Nevada
Year, Model & Trim Level
1992 Explorer 4 x 4
I have searched the transmission section without seeing an answer to this. So, if the information is in there, please post a link, not just "look at the sticky", because I already have. That said, if this hasn't been covered before, I'd be surprised.

I had an overheating issue. Got a busted upper radiator hose. Shortly, after, and before I had diagnosed it, I had transmission issues. When cold, the transmission ran great. As it got hotter, the transmission worked less well and then quit working all together. By quit working I mean, at the end of a five mile trip, I couldn't drive up a 5-10 degree incline until the system cooled down. Then, it would drive again. According to the guage, the engine is not getting hot, and there are no signs that the fluid is boiling in the radiator or that it is losing coolant.

Some background. First, I fixed the radiator hose. Then, I replaced a stuck thermostat. I thought I had fixed everything, until the trans issue reared up again. I'm now thinking I broke down the trans fluid when it overheated and I should replace it. I'm not sure the best way to do that. I'm kind of concerned about a pressurized flush, but I don't know if a filter change and pan drop will change enough of the bad fluid (if that is the issue).

Any help would be appreciated. Thanks.

BTW, thanks to mrcribb for the following post on changing the thermostat. It helped immensely.
How to: Change thermostat 1991 - 1994 Ford Explorer w/pcs
 



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my trans kinda changed it's own fluid after the steel line let go. repaired that and a week later the other one let go. repaired that and 2 days later the rubber line to the cooler let go. so after emptying the pan through the lines 3 times and refilling with fresh I figure the fluid was changed. you can do the same by tapping into the steel line that goes from the trans to the upper radiator. it changes the appx 3 qts in the pan without removing the pan. use a pan that holds 3-4 qts, disconnect line and start engine. reconnect line and refill. you won't get all of it this way but enough. use fuel line and clamps to repair steel line.
 






You don't need to cut the steel line, just disconnect the rubber line from the cooler. Plus, disconnecting the line won't drain the transmission pan, it will only drain what's in the cooler.

The general procedure that a lot of us like is to have about 12-15 quarts of ATF on hand then you can either choose to drop the pan and replace the filter or skip that step. If you've never had the pan off, it might be worthwhile. But, replacing the filter is kinda useless, it's not really a filter, more of a window screen. Now, disconnect one of the cooler lines and start the engine. After 2 quarts or so has come out, start pouring fresh ATF into the dipstick filler neck. Keep pouring in at a rate similar to how fast it's coming out via the cooler line. Don't stop filling until the fluid coming out is clean. Bonus points for having someone in the driver's seat, with the emergency brake on, shifting through the gears. Once it's clean, shut off the engine.

Now, I'd recommend replacing the rubber hoses. My local NAPA has Parker Push-Loc 3/8" hose that is pretty awesome for this application. It takes much higher pressures and is a thick reinforced hose, it'll never let you down. I'd also recommend installing an in-line filter like a Magnefine. It will greatly help and clean up the fluid. You can take a look at my signature to see what proper filtration for an A4LD does.

All this said, this is just assuming that new fluid will help. It could be toast but an overheating engine shouldn't really affect the trans fluid. The coolant could superheat the ATF but if your coolant got that hot, it would probably mean your engine is fried. Still, new fluid can't hurt, especially doing it with the method above.
 






Thanks for the replies. What is the best way to see if the cooler is working properly?
 






have a flow check done on the cooler
 






If you could check main pressure, it would tell you a lot. Things expand when they heat up. If a clearance gets wider and the fluid bleeds internally, less pressure is available for working the clutch packs, etc.

If your pressure maintains, and it won't move, than you may have internal mechanical issues. If it drops, you most likely have a pump or fluid issue.

I have also seen hydraulic pumps loose flow potential once the fluid warms up, both through thinning of the fluid and worn clearances within the pump.

I would certainly try changing the fluid and adding Lucas or other treatment to it. If it works then you're good for awhile. I've gotten significant time out of very worn forklift transmissions using Lucas additive. Some of these units with more than the equivalent of 500,000 miles on them.

Either way it sounds like you are probably gonna be looking at a rebuild in the near future to fix it long term. Certainly let us know what you find.
 






Just thought of this... is the fluid pink and milky looking instead of red and clear? It so you most likely got coolant in the trans. If the cooler in the radiator failed, then your trans is junk. Excessive heat could have made the cooler fail. Ethylene glycol dissolves the friction discs in the clutch packs and will cause trans failure.
 






The transmission stalling on a 5-10 degree incline sounds to me like the fluid is low.
I just had my pan dropped and filter changed, and it took 5qts to top off. Just that much new fluid made a huge difference in the shifting.

I have also heard that some guys have a drain plug machined into the OEM pan so the fluid can be changed quickly and often.

I also took Nate's advice and had a Magnafine filter installed at the cooler.
 






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