C6 shutters in reverse.

JacobHansen

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Ok guys im looking for some help. My 4x4 c6 transmission. Shifts a little late on cold mornings. But smooth shifts. Normal shift is around 1800-2200rpm late is around 3000rpm (in my opinion) Its always been a little late going into reverse. Not more then 4-6 seconds. Witch seems like forever when your trying to back up. Now although its not often, every one in a while it will grab and drop reverse gear. Like really quick. Like if a gear was stripped or something. Apply heavy throttle and it goes fine in reverse. I haven't yet been in the pan. 2nd gear did experience some slipping a while back from lack of fluid. What should be my next steps? Rebuild time or maybe an adjustment? I was planning on a filter and fluid change soon anyway. But hate to throw money away if its rebuild time.
 

Cubey

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My F250 is like that. Just put it in park or neutral and give it some light throttle for at least 30 seconds before you try to drive it. These old transmissions sometimes have "morning sickness" where you have to get the fluid running good before it'll work right. I had a 78 Dodge A727 (Dodge's C6 equiv) that did the same thing. Honest transmisson shops will tell you that there's nothing you can do about it. The fluid is draining out of the torque converter overnight and has to refill, hence the slipping. Let it fill up by helping it with some throttle and it'll be good.

On really cold mornings, the F250 won't even shift into gear at ALL at first unless I give it throttle in P or N for at least 30 seconds. But after that, it has no slipping, it engages R or D perfectly from P or N, and shifts perfectly when driving. I don't try to drive it until I feel it quickly shift into R or D like it should.

Once I was in a hurry and didn't warm/pump it up enough, and ended up backing out into the road and couldn't get it to engage into D until I put in P or N and gave it throttle for at least 5-10 seconds. Felt like forever. At least it was a residential street and the one vehicle stopped for me and didn't start blowing their horn.

(Edit: Actually, come to think of it, it does seem delayed to shift into second at first on cold mornings at low throttle, but after that first time it's fine. I still think it's a fluid filling the TC issue)

My RV doesn't have it as bad but it's transmission hasn't been rebuilt. The F250 and ol Dodge's had been so something about rebuilds seems to cause it.
 
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franklin2

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It's hard to kill a c6. If your fluid looks dark and smelly, changing it can do wonders. If you want to pull the pan, check to see what's in it. Some black silt with some gold dust in it is normal. Large chunks of metal or or large pieces of what looks like paper is not a good sign.

Take the inspection cover off the flywheel and turn the engine by hand and see if a drain plug comes around. The flexplate will have a large hole in it, and a drain plug will be in the middle if you have one. Turn this around to the bottom and drain the torque converter. That along with pulling the pan will get ALL the old fluid it out. It will take approx 13-14 quarts to fill it back up if you drain the torque converter. Only about 3 or 4 if you just pull the pan.
 

Cubey

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Take the inspection cover off the flywheel and turn the engine by hand and see if a drain plug comes around. The flexplate will have a large hole in it, and a drain plug will be in the middle if you have one. Turn this around to the bottom and drain the torque converter. That along with pulling the pan will get ALL the old fluid it out. It will take approx 13-14 quarts to fill it back up if you drain the torque converter. Only about 3 or 4 if you just pull the pan.

Good info to know.

Who knows when, if ever, my C6 has been serviced. The fluid looks healthy though, nice and red still, so it's possible it's been serviced at some point in almost 35 years. No signs of problems, just the very late shift points that may have been intentionally set for a lead foot who wants to get this brick (RV) up to speed fast. (Approx 25mph for 2nd & 35mph for 3rd). Adjusting VRV and putting an adjustable valve at the trans vac line does nothing to change it. I'm thinking it may have been pulled and had a shift kit of some kind put in at some point.

I would like to drop the pan and replace the filter, in the event it hasn't ever been done. I don't really want to deal with the TC, so I'm thinking a pan with a drain bolt might be a good idea. Just occasionally drain the pan and refill it. Eventually all the fluid will be diluted into being all fresh fluid. That or just pay a shop ~$120 to do it all and be done with it.

But eh, if it ain't broken and the fluid looks good, maybe it's best to leave it alone for now.
 

Garbage_Mechan

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The torque converter drain is a great thing......probably more than half the fluid won’t get changed if you don’t drain the tc. Not too hard really. The main band does have an adjustment..... not very hard just need an inch pound torque wrench. The time delay is probably old hard seals that take a moment to seal and apply the clutch/band.
 

Cubey

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If the C6 goes, I'd consider an e4od swap for potentially better fuel economy, if can score a good priced used standalone controller. Quick4's seem too come up on Ebay compete used for $500 or less. They are about $800 new.
 

JacobHansen

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Ok so i started it up this morning. Went into gear fine back right up. I let it run for a little while. Maybe 4 minutes then checked the fluid. It was way over full. Im going to go ahead and change the fluid. Change the filter thing too. Could over full cause this? It only has the problem it seems when its hot. The late shifting is fine by me but I don't like the gamble with reverse. I don't force it if it starts bucking I just park it. To prevent any damage. If the fluid change helps I should have it adjusted?
 

franklin2

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Being over full can cause problems. The fluid being too high gets up into the spinning parts of the trans, and this stirs the fluid up and makes it foamy. Foamy fluid doesn't work well in the trans in the controls and the pump.
 

IDIBRONCO

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Take the inspection cover off the flywheel and turn the engine by hand and see if a drain plug comes around. The flexplate will have a large hole in it, and a drain plug will be in the middle if you have one.
You should have a drain plug. The hole that it's located in will be next to the convertor nuts. IIRC, there is a large hole next to each one of the convertor nuts.
 
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