C6 help

[Rot Box]

It's too hard to have a broke down truck sitting there staring at you... Expecially if it's an IDI

I posted awile back about a $300 someting dollar beauty that I bought for the turbo. Well it turns out (before I stripped out an injector line/injector ) that the mystery engine rebuild seems to be a good one. The engine runs great after I worked out a few bugs and it seems to have very good compression. It no longer has the turbo, but all the stock pieces are now in place with a really nice new exhaust system. I am having one issue though...

The "rebuild" C6 transmission acts like it has very low line pressure. I'm no expert, but when you stab the throttle nothing happens. The kickdown is in place but it is not putting power to the ground. It is slow to get into reverse untill its warm and that seems normal I think.

Also There was (key word: was) a vacuum deal mounted on the IP but it was broken so I bypassed it. What is that thing called, and would it have anything to do with my problem? What are some checks -if any- that I can do to see what condition my trans is in? Thanks for any info or help you can give me

Andrew

 

[HammerDown]

...

Also There was (key word: was) a vacuum deal mounted on the IP but it was broken so I bypassed it. What is that thing called, and would it have anything to do with my problem?

Andrew

That thing you bypassed is the VRV >vacuum regulator valve.
Doub't it has anything to do with reverse but I know when mine was going bad it made for very high and hard 1-2 shift. And I usually had to ease off the throttle to get a shift.
Kinda hard to mess up a C6 unless you burn it up with real soft sloppy shift settings >(vrv) or burn the fluid >no trany cooler and towing a mile long row of chebys.

 

[typ4]

lewiston, as in Idaho. your reverse high clutch seals are hard. I bet it wasnt rebuilt, just serviced. I fyou have a trans buddy it is a reasonable fix, if you dont, get it here, the trans, and I can fix it cheap. Oh and correctly.

 

[Rot Box]

Thanks for the quick reply's

Around here an under carriage can go from looking new to covered in grease and dirt in just a few weeks, and the outside of this C6 is really clean. There are sharpie pen sribbles on the torque converter suggesting it might have been replaced as well. I guess looking at the outside doesn't mean much, but someone must have done something to it.

The fluid is very clean and red. My guess is that the trans is like the motor was and just doesn't have any of the external componants installed correctly. Does anyone have a diagram of the vacuum lines and such for this transmission? That would help a lot I think...

Nope Lewiston Utah Thanks for the offer, but unfortunatly thats a bit of a drive

 

[david85]

That tranny won't work right without a functioning VRV on the IP. I'm not sure if the reverse would normally be affected by that, but theres a really easy and safe way to find out. Pull the vacuum line from the back of the transmission to see if it has any affect on the engagement time. No vacuum to the transmission should cause maximum line pressure and high RPM upshifts.

Don't drive it that way, but if the transmission seems to grab 1st or reverse properly from park or neutral, then you might only need a VRV and nothing else. Its a long shot, but won't cost you a thing to try.

Theres some Tech info here: http://www.garagenet.biz/forddiesel.htm

Look at about the middle of the list for the info on the C6. Its 1985, but basically the same system.

 

[typ4]

vacuum does not affect a c6 going into gear properly when stopped. it does affect upshifts and as said line pressure. Reverse should not be delayed, does low gear work? second? third?

active elements
c6, low /reverse clutch
reverse/high clutch
second gear, band
direct clutch for all forward gears
low roller clutch in rear for normal d starts

operation of said elements
in low gear, direct clutch, low roller clutch ,or low discs if in manual low
second gear, direct clutch, intermediate band
high gear,direct clutch, reverse high clutch
reverse, low reverse and reverse high clutch

the c6 is the ONLY automatic that can be operated without the kickdown becausethat is all it does, it dousnt affect line pressure.

so by a process of gear operation you can figure out what is bad.
You could also have a junk pump, seen hundreds of these bad due to improper install procedures.
Now you may have a faulty torque convertor, drop the pan and check for metal. go from there. Then come back and ask more questions.

 

[Rot Box]

Thanks you guy's thats just what I needed

All gears work, and reverse engages well when warm. Acceleration feels like mush--barely enough power to pull on to the car hauler. If I apply the brake slightly and give it some throttle the engine will lug down, and the rear tire won't even think about spinning. Also the shifts seems sudden (almost too low of RPM), but never slams into gear.

I'll track down a VRV and replace the vacuum lines and go from there. A new filter and fluid won't hurt either

 

[Agnem]

A properly adjusted VRV and the doohicky it attaches to on the transmission are key parts. A C6 is no good without them.

 

[Pino2234]

vacuum does not affect a c6 going into gear properly when stopped. it does affect upshifts and as said line pressure. Reverse should not be delayed, does low gear work? second? third?

active elements
c6, low /reverse clutch
low roller clutch in rear for normal d starts

operation of said elements
in low gear, direct clutch, low roller clutch ,or low discs if in manual low

My truck starts in 2nd gear when I go from Park to Drive.

The only way it goes into first is if I put it in manually on the column.

You mentioned the active elements and operation of those elements, however, since I have this problem how do I adjust these parts. Or does the transmission have to come apart to repair this problem? Thanks.

 

[sassyrel]

rot--go to a auto parts store, and get a qt can of trans-x-----the can is the same color as dark ford blue--8.70 last time i bought a qt. drain qt from your trans by loosening trans cooler line, then add the qt of trans x to yours----drive carefully for a while so you dont glaze the clutches any worse than they already are---trans-x will soften the seals back up, not in 10 minutes--but it will do it--been there lots of times----this aint no guarentee, as you may have already glazed the clutches---then they dont like to grab much--and when they are getting glazed--they are wearing off---------------------

 

[Diesel JD]

Try this: shift the C6 through the gears manually on the column and see if that makes an improvement. The thing I would be worried about is that the transmission vaccuum modulator on the back on the transmission where the vacuum line plugs in has been bypassed or installed incorrectly or an incorrect modulator was installed. Also there is a pin that MUST be installed in that modulator otherwise you will subject it to constant vaccum and it will blow out seals and eventually do hard parts damage. I learned this the hard way years ago. As to the 2nd poster, you're running over 1st and right into 2nd, and can hardly feel the shifts. This is called stack shifting and it can damage a C6 also. The VRV is usually adjusted by the seat of your pants. Dieselmann's IDI page show's the correct procedure to adjust with tools but it always confused the heck out of me. One reason I went manual is that this VRV is so critical but it is dealer only and I'm afraid it may be headed for obsolescence. It's expensive too. You might hit up towcat or one of the other members for a good used unit. Good luck.

 

[Pino2234]

As to the 2nd poster, you're running over 1st and right into 2nd, and can hardly feel the shifts. This is called stack shifting and it can damage a C6 also. Good luck.

This is not the problem. I had this truck for a few years and I know that first shifts fast but not that fast. The biggest why that I can tell is if I start in Drive on an upgrade. It just starts in second. No first at all. It started happening last week. It did it earlier this year, it seems like it happens in colder weather. Not sure.

Also that modulator on the back is only like $20 I dont have any problem changing it however there is like 3 different versions of it.
-A green stripe
-A purple stripe
-A black stripe.

If anyone can tell me what those stripes mean that would be a BIG help. Thanks.

 

[Diesel JD]

I'm sorry I don't remember which is the correct one, someone here will know. I still have a C6 in the garage maybe I can go look and post back later. I think the pin in the modulator is important as is it's adjustment. Usually shifting problems are from the VRV though not this modulator. Another thing to check is the vacuum pump itself. It should be putting out about 22"Hg if it is in working order at the VRV ports, it'll still work with lower vacuum but much lower becomes highly sketchy and it works but just not quite right.

 

[osus86diesel]

I just bought the modulator. Green stripe on my C6 2wd.

I am having a similar troubles with my C6. It seems to be "stack" shifting. no matter if i drive easy or give 'er hell, it seems to miss second gear. The modulator did not fix the problem. It was only 12 dollars from auto zone.. no big loss.

How is the VRV adjusted?

the vacuum pump on mine is new, put it on last year.

 

[david85]

I wonder if its a band adjustment problem. C6s have an adjustment on the side of them for the intermediate band if I remember right. I'll see if I can find some info on it.

Sorry, mostly E4OD data in my head