Need help with C-6 problems - Long Post

[Mojave Red]

This event happened a couple of weeks ago but the problem persists. Let me set the stage: It's the first day of our two week block leave (Army guy for those who don't know) and my wife and I, along with a couple of other Army families, are headed to the eastern Sierra Nevada for a little fishing/camping. It's approaching 100 degrees outside as I start up the long grade on the 395 north out of Ridgecrest. I have my 2500lbs camper in back. Everything seemed to be going fine until my transmission just let go - like it shifted to neutral. I pull over, get out and immediately smell burning clutches. Lucky for me I travel with a gallon of every type of fluid imaginable. So I dumped a gallon of transmission fluid into the transmission, barely registered on the stick, and began to limp towards Lone Pine. I'm already getting the look from my wife . To make an already long story short, I dumped three gallons of fluid into the transmission between Lone Pine and Bishop (about 60 miles). A guy at the only transmission shop in town tracked my fluid loss to the vacuum modulator - seems the vacuum pump was sucking the fluid out and spewing it right onto the road. $110 dollars and a new modulator later we're back on the road. Made it the rest of the way to June Lake and back home without major mishap or loss of transmission fluid.

The thing is, the transmission is not shifting right. It doesn't alway make it back down to first after a stop, and I usually have to back off the throttle to get it to up shift. I'm sure I caused some damage when I ran it dry, but still shifts solid without slipping in or out of gear. I've long suspected that my torque converter has gone south but I don't know how to properly diagnose that.

So I need your suggestions, opinions and thoughts as to what to do. Is it rebuild time? Could it be the wrong modulator or is it out of adjustment? VRV? How to you tell if your torque convert is bad. It seems like I have to get it spun up pretty good before my truck starts rolling with any type of load. Please help. I'm at wits end over this. My wife won't accompany me on anymore camping/fishing trips until I can guarantee no more problems. The transmission is the last major component on my truck that I have not replaced or rebuilt. Not sure if it's original but it's got at least 70,000 miles with me - and I've been pretty ******* it. Enough said...

Thanks much, Brian

PS: we caught lots of fish...

 

[Diesel JD]

Well, if you didn't completely run it out of fluid and burn the whole thing up, its probably avaccum related issue. Bear in mind that the first shift is often very soft and almost unnoticeable. Over at this site there is the info to properly adjust the VRV(and of course its alwasy possible you need a new one) www.intellidog.com/dieselmann Looks like you need a vaccum pump and vaccum gauge and I really was too confused by the whole thing but apparently some folks have gotten good results with this. Alternately, go to a reputable tranny shop. You might ask around and see who Uhaul uses, since they have a lot of trucks and vans with the C6, gas and diesel and of course the E4POS. Similarly, you might call the school bus maintenance department and see who they use. Again, you want someone who knows about the C6. And someone who isn't a ripoff artist.
J.D.

 

[typ4]

Ther is probably some crud in the governor from the slipping, clean it, easy if 2 wheel , check mod adjustment with small screwdriver in ,for later shifts out for sooner. I do about 50 c6's a year for airport equipment, they can break an anvil those people

 

[flatlander]

On the driver's side of the transmission near the shift linkage there is a port that you can hook a pressure gauge to and see if you have adequate oil pressure in the transmission. It is just in front of and a little higher than the band adjustment screw which is directly under the shift linkage. I can't post pictures (I don't know how or have the equipment to do so), but I can check my haynes for the proper pressures you should see in neutral, forward and reverse. This will at least tell you if you have pump or torque convertor problems.

 

[Agnem]

Sounds to me like you might have gotten the wrong modulator installed. They all look the same, but are color coded. That would have been a hard one to find before you left! I imagine your vacuum pump is properly lubricated now. Althought, it may also be faulty now as well. If you don't have a vacuum guage installed in your cab, get one.

 

[Mojave Red]

Mel

You might be right about the wrong modulator. The one I have now looks different than the old one. I think we have a decent trans shop here in town. I just wanted to get a baseline of information before I went there. The shop in Bishop was all too ready to sell me a rebuild to the tune of $2000. I think the management was pretty upset with the mechanic when he got me on the road for $110. I'm pretty sure my vacuum pump is still ok as all my other vacuum related equipment is working fine. I'm hoping to avoid the cost of a lot of diagnostics (shop time) and then still having to replace my transmission. If it's shot, I can R&R it myself.

Thanks for the help, Brian

 

[Diesel JD]

Just to clarify, which color stripe is the correct one for the C6 diesel? The other thing is that the vaccum modulator must be installed with the proper pin in the vaccum line. Otherwise you may subject the transmission to constant vaccum, in which case you will cook it as I did mine. $2000 for a C6 rebuild...WHAT?!?! Its good you can R&R yourself, but hopefully it is something cheaper and easier to work with.

 

[IDIeselman]

I believe the purple stripe to be correct, If you are questioning the pin, Remove the bolt from the modulator and pull it out half way, while putting the modulator back in it should have about an 1/4 inch of sprung resistance before being fully seated against the trans. If this is correct buy a can of trans x from your local parts store and follow the directions, I have personally used this and it has brought transmissions back from the dead.
Tim

 

[towcat]

brian-
if you can limp it up here(norkal), I can get you taken care of with shift kit for 1k. I have two diesel C-6's left so hard parts is not an issue. imho, when the trans got sucked dry, the clutches got burned and there's no going back when that happens.

 

[Mojave Red]

Calvin

I might just take you up on that. Because of our schedule down here, we would have to do it in a four day weekend or I'll have leave my truck up there until my next break. I'm pretty sure I could make it up there with no load. I'll be in touch.

Does anyone have a picture of the correct modulator?

thanks, brian

 

[adrianspeeder]

2K for a C6? E4OD maybe, and thats pushing it.

Adrianspeeder

 

[Mojave Red]

The Bishop Ford dealer quoted me $1200 for the transmission. The shop wanted another $800 for RR. My wife over heard the shop manager scolding the Ford parts guy for quoting the too low price of $1200. They assessed the situation: Three families on their first day of vacation = this guy will pay anything to get back on the road.
There was some other poor sap and his son camping in the shop parking lot while their E4OD was being reworked. I suspect they get a lot of broke down travelers there.

brian

 

[Agnem]

I rebuilt mine myself for less than $500, and that included some upgraded parts, and some parts that maybe normally wouldn't need to be replaced. I can't swear to the stripe color. I thought it was green or orange. If I can see it today, I'll post what I saw.