Hello again. I have a '74 highboy with the c6 transmission. Last spring I was chained up and horsing my way through some pretty dense snow drifts. When I started to get some wheel hop I would stop, back up, and hit it again. I made it through without even thinking that I was abusing the transmission. Ever since then it takes a while to go into gear when shifting from park after it has been sitting with the engine off for a half hour or more. Once it goes into gear it seems to work fine until the next time I turn it off for a while. Seems to take longer to go into gear when it's cold outside. It also seems to go into gear quicker if I overfill the transmission slightly. I don't know automatic transmissions at all but I'm thinking "pump"? The fluid has never run low. Anyone know what I am in for? Is it going to get worse? I might be able to live with it the way it is now.
I'm off-grid and solar power isn't the best this time of year but I'll check back when I can. Thanks.

 

sounds like your facing some transmission work to this old mechanic , lazy movement from park into drive means problems starting at the pump just inside the case under the convertor .
what i would first do is a proper pressure check than drop the pan to see whats inside . meaning metal and clutch plate material.

 

See what the fluid looks like. Maybe just low or burnt.

 

T

Thank you. Fuid is up an not burnt.

 

Thanks. I will start with those two things. Will have to wait until spring to crawl under it though.

 

Not a transmission expert but would ask 2 questions. Because you were Ramming thru snow drifts. Is all underneath clean and clear? If you have a passing gear kick down linkage, is it jammed with frozen snow/ice?? On the passenger side of transmission, thinking there is a Vacuum Modulator Valve. A steel tube from intake manifold goes down to it and a rubber hose joins the valve to the steel tube. Is all intact or possibly the hose is knocked off or line damaged??? Both have to do with smooth operation of the transmission and not functioning properly the transmission will be confused/off normal. Cap

 

hear that as i know how the weather can be in WY, as when i drove semi's i got stuck out there too many times sitting for days outside of rock springs

 

Snow was only about 6 inches deep. It was the remains of my snow machine trail so it was dense but it didn't even come up to my axels. Thanks though.

 

I finally am dealing with my transmission. I did not pressure check it. Curiously the last two times that I used the truck the transmission worked perfectly. The weather has been hot but I fired it up yesterday morning when it was still cool and it dropped into gear immediately then too. Nosed it into my shop and dropped the pan. Fluid looked great and no sign of any material in the pan. Filter looked good too but I put a new one on and put it back together. Haven't put fluid back in yet. Now I'm wondering about the whole Type F versus Dextron Mercon thing. I was told years ago by a reputable mechanic that since I bought and installed a rebuilt C6 in the '90's that I didn't need to use Type F anymore. So I've not used it ever since. When I dropped the pan yesterday I noticed that the fluid did not readily drain through the filter screen unless I helped it by pushing on it with my finger. Even though the screen looked clean. Now I'm wondering if Type F is thinner and maybe I should be using it? Anybody know the difference?

 

I can't tell You what the difference is, I never knew! They Both had to be for cold weather operation. As a LOL, what were the choices back then, Type A, GM(before Dexron)I think and Type F, Ford. They may have had different anti wear recipes or for smooth shifting, no chatter

Is your filter actually a fine screen as if you can reverse flush it clean??

One of my old original questions was, does the transmission have linkage to kick down shift for passing and could it have been stuck in the down position in the snow n cold weather. If stuck, the transmission will be confused as to what gear it needs to go into. And may also have a vacuum modulator on side of the transmission with steel line going to the intake manifold that has to do with up and down shifting??

Now this is Stretching My Memory. Doesn't the C-6 have 2 Drives at the shift lever on the steering column?? The one closest to N is for normal driving and the other drive next to it starts the vehicle off in 2nd gear. Especially in cars it was a good feature in Ice and Snow conditions as to not break the rear wheels loose, as 1st gear would from a standing start.

Cap

 

I did a bunch of studying on ATF types yesterday. Bottom line is that I can throw anything in there and even mix them. Racers still use type F because it shifts harder.
I bought Fram general purpose ATF and just got done filling it, pulled it out of the shop and I'm letting it settle.
There's D 2 1 on the column. I think it might start out in second if you put it in 2 while stopped. I'll check it out tomorrow.
Linkage was all good. I've had linkage problems before due to bushings wearing away. Bought a modulator then but didn't have to use it.

 

I drove OTR some too. Didn't you love getting going again after a two day wait, in that huge wad of trucks most of which were governed within a mph or two of each other?
So what I did was drain all fluid including torque converter and changed the filter which as I said before looked clean to me. No dirt in the pan either. I put Fram ATF in it. It still acts exactly the same. Only difference is that there is a fairly loud whirring whining and sporadic hissing type sound that mostly goes away after it warms up. Used to be that if the truck sat for a while (it leaked around the shifter seal while it was sitting) it might whine like that a little when I started it up. I would check the fluid and it would be low so I would top it off. This time I kept adding a little at a time hoping that the whine would go away. It's a little over full now but the sound didn't go away. I used it yesterday and put over a cord of wood on it and it pulled a couple of steep hills with no slipping or noise or anything. I have a pump and a pump puller in my Amazon shopping cart but I'm wondering if I have anything to worry about.

 

Again not very knowledgeable on the inside/guts of auto's. Just sitting there in park, if you rev the engine, does the whine increase and decrease with engine speed? If So, nothing else in transmission is working I would think pump or bearing(s) in input of transmission, worn. As you worked the truck, ALL seemed fine, shifted well, except noise/whine?

 

Yes. Whine increases with rpms. Sounds like it's coming from bellhousing/pump area. Goes away once it warms up. Takes a minute or so of high idle before it will drop into gear. Then everything works fine. Today I unloaded the truck. I don't remember hearing the whine today when I started it up. Didn't realize it until later. I've been cussing a blue streak every time I hear it. I think I would remember hearing it. I'll let you know what I hear when I start it tomorrow. Neighbor says I should try putting some Lucas transmission treatment in it.

 

I believe in additives/treatments and have used various over the years. Not that they're for Auto Tran's but Marvel Mystery Oil, Rislone, BarsLeaks, favorite's. I'd definitely try, not gonna hurt. Let Us know how you do.