Well guys im here seeking advice... grandfather's 71' f250 60k original miles on this C6 and fluid and filter was replaced within 5k miles. long ago it was used for work and vacations with in-bed classic camper. the fluid is definitely dirty now, and ive read up on that band and the possible adjustment screw/nut... question is presuming i make the band adjustment and it doesnt fix it, 1st and 2nd gears hold nice and firm. should i really tear down the entire trans just for a band? the truck is a stock 360, and i will be using it to haul around my boat (5k max Bayliner 19ft i/o) and the occasional u-haul auto trailer once my hitch gets installed.

 

What type of fluid was put in it ?

 

please define 'wont hold 3rd'. Slips in 3rd gear or downshifts to 2nd? How long has it had issues?

 

dexron/merconIII stuff, suppose it might need type F, but i am pretty sure the dipstick says mercon fluid(i hope, dont want to look like a rookie). Now, with the holding description, both Reverse and 3rd shift fine and holds the gear during initial warm-up(5-10 minutes of driving)... Id say after 10 minutes of Los Angeles and trans is up to temp, the shift from 2nd to 3rd is really lazy. i have to let off the gas in order for the clutches to engage 3rd, or else it just seems to continue to stay in a "grey area" between 2nd and 3rd. engine revs but i get no additional drive. once it shifts, it accelerates but with slight slipping. However it does a weird "fall" of engine rpm's say when coming down hill above 55 mph when there should be engine braking. also this is when reverse would shudder, at the completion of my trip across town. this is all at the trucks empty weight of 4900lbs.

 

The lag or surge in between shifts is known as "flare" --when the transmission does essentially nothing for the amount of increase in engine RPMs and doesn't want to advance to the next gear.

The easiest thing you can try is to adjust the band (per the shop manual procedure), since this can be done external to the transmission and doesn't require opening it up.

When a transmission starts doing this though, it's usually an indication of worn clutches (assuming that the fluid level is up to spec).

If the band adjustment doesn't work, it's probably time to start planning that rebuild of the C-6.

 

Drain some fluid and see if it had any shavings in it. They can make the pistons stick in the bores in the valve body, especially when warmed up. Is the kickdown hooked up and functional? You can also temporarily install an old oil pressure gauge on the cooler circuit to monitor line pressure. clutches/bands need pressure to hold under load. good luck.

 

Rut Row Raggy. There's your problem. Should have put Type F in it. 1977 was the 1st year Ford put Dexron in the C6. A person can put a little type F in a tranny where there was Dexron, but not the other way around. The tranny's clutch packs were used to type F. Now you hit them with Dexron. So they will slip. Try draining the trans COMPLETE. Torque convertor included. Flush and refill with type F. Hope it will come back. But prolly won't.

 

That's likely to be difficult to only drain out a little fluid since Ford, in its infinite wisdom, didn't put drain plugs in the transmission pans.

This means having to remove pan bolts and once the pan breaks loose from the gasket, the fluid is coming outta there. All of it.

AFTER the pan is removed, you could put a drain plug in it for the NEXT time.

 

Full trans drain minimum preferably a flush to flush out all the friction material in the trans. If you drain it do not forget to drain the torque converter.

Since you used Dexon in it you need get a pure as possible Type F fill.

There is good chance are you have grenaded the transmission. More specifically the clutch packs and bands.

Try refilling with Type F and see how it does, if this does not fix the slipping the trans is toast.

Either way you have severely shortened the life span of the trans.
If the pan is full crud (black dust looking stuff) the trans is more than likely toast as that would be all your clutch and band material. If you have no crud the gods were smiling on you and you may get away scott free.


When you described what it was doing it was classic Dexron in a Type F trans symptoms.

If you get the trans rebuilt the rebuilder will likely tell you that the trans is good for Dexron cause they used Dexron compatible clutch packs, don't do it still use Type F. To truly make a Type F trans Dexron compatible requires upping shift pressure and clutch pack holding pressures.

This topic came up a while ago on the forum and then it was stated if in doubt use Type F.

 

You can pop the torque converter drain plug and drain a bit that way. In this instance you will be looking for clutch material in the fluid. It will suspend in the fluid unless it has been sitting a for a while.

 

What about via the torque converter drain bolt?

 

Easiest way to remove/swap/flush fluid is to disconnect cooler return line, and crank or start motor. This will also push fluid thru converter. You will never get all Dex/merc out, but should be able to get 90% or better with 1.5x the capacity of type F.

The return line should be the one on the rear of the trans. Connect a piece of hose to the line and run into a bucket/jug/pan. If you can keep track of what comes out you know how much to put back in (which is where an old gallon oil jug is nice, as it is graduated) I would do 3 qts at a time, pump 3 out, add 3 into dipstick. repeat. move shifter through gear positions to get new fluid into valve body.

I would start by pumping out a few qts and see what's in the fluid and go from there. If no shavings, swap fluid, and test drive. If improved, drive 2 complete cycles and swap fluid again. that may be $200 of fluid.

 

If you have debris, particularly metal shavings, coming out of the transmission or especially out of the torque converter, you need to flush the entire system --transmission lines, radiator cooler and the torque converter before firing the the engine back up. Although, if metal shavings are present in the torque converter, you're better off replacing it with a new one.

You would need to flush the torque converter with it out of the transmission. You can get a small, inexpensive pump that can be run off of a drill motor to circulate clean transmission fluid through the lines and the cooler in the bottom of the radiator, before hooking everything back up and firing the engine up for the first time afterwards.

Being lazy or short cutting this can easily lead to a complete transmission failure.

 

If it needs a rebuild, it's actually rather cheap and easy to rebuild a C6. I can do two of them comfortably in the course of a day and not hit overtime. If I did them more often I could probably do three a day. The only tricky part is setting the total end play.
You can also rebuild it to run on Dexron so you can use a cheaper fluid, just make sure to etch it on the stick.

 

Like Six is saying, ive read up on this C6 rebuild and anyone who's done one says it is quite easy. i'm just gonna pull it down, since its only a 2wd truck, and redo it. Recommend brands or kits now. Cheap one on Rockauto is only 120 bucks or so...