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C6 trans lost forward gears (mostly)

Posted: Tue Dec 11, 2007 11:22 pm
by rlaggren
Al or anybody w/C6 tranny knowledge: I'd like to know if there may be any cheap scenarios to get the van running again, light duty, for a couple thousand miles.

Last week I heard strange noises at idle and found the ATF low (I think - I've always found that hard to read on the stick) - so I added some. I'd been checking once a week for a couple months last summer but didn't see anything change so... Wasn't paying attention.

Next day just as I was reaching the top of a hill (hard pull for about 100 yards), the engine revved and I just barely made it up. The van didn't want to go foward after that, although it would creep up to speed eventually, whining all the time. I tried a mile or so on the flat but it seemed to get worse (more slippage or whatever) and I had it towed home. It's got reverse no problem and I can creep around the parking lot, slowly, with some whining. ATF doesn't look new, but I don't know what bad ATF look like.

I'd been planningn to retire this van, but it'd be a lot more convenient to have it driveable - I'd convert it to a storage unit. I'm quoted $1200 for the "do the right thing" job and that's a little tall right now.

If the cause is obvious (to you) can you suggest any effective 1/2-way fixes appropriate to minimal usage. Then I could look around armed with some knowledge. This isn't the kind of work I've done or plan to do myself.

Thanks for thoughts.


Posted: Wed Dec 12, 2007 2:43 am
by kassim503
Im guessing it would be a ford van, I know this sounds kinda obious, but did you check the fluid level? After you said the van slipped more when on flat land, it seems like a low fluid level condition, because if I remember correctly, the pickup screen is in the back of the pan on the C6.

You could check the fluid condition if you take some of the ATF off the dipstick and dab it on a white napkin, it seems to be working its way thru the fibers and is red or pink in color its good. If its brown or clear and dosent try to work thru the fibers, its bad.

I could only say change the ATF/filter and load it with high mileage and anti slip additives, even though I never use that stuff, you could try it. It may be a bad seal somewhere inside, reducing line pressure. Im not sure if the additives would help. Oh and while you have the trans pan off, you can also try to check if the valve body is loose, and if there is chunks of gasket or seal material in the pan.

Also, your clutches are gonna be in really bad shape, probably burnt to a crisp, so without a rebuild, I wouldn't be towing with it or relying on it for a while.

Posted: Wed Dec 12, 2007 7:09 am
by asavage
On a C6, with that symptom, my advice would be: don't spend a minute on it. You have to go directly to a JY trans. Unless it's 4WD, a JY (or CL) C6 will run you well under $200, probably under $100. New filter & pan gasket, torque converter seal, extension housing seal, and a case of ATF. Blow out the cooler lines as possible -- there is an aerosol can of flushing juice that makes this easy without hassle.

Downside is -- getting the trans in & out. The rear crossmember can be bitchy on 80's E- and F-series. Rent a tranny jack if you have the spare $20, or use a std floor jack and chunks of wood if you don't.

Posted: Wed Dec 12, 2007 5:24 pm
by rlaggren
Thanks Kassim, Al

That's an informed opinion I can use.

It had plenty of ATF when it failed, but only because I filled it the day before. I guess I'm looking at a used C6 and some shop space.

Fortunately (if, hopefully, I'm remembering the regsitration dates right) I have almost a year before this van has to be functional beyond creeping around the lot. So now I know one thing I'm doing next s.ummer <G>


Posted: Thu Dec 13, 2007 3:18 pm
by redmondjp
Well, at this point you've got nothing to lose, so try adding some of that transmission 'leak stop' additive (one or two bottles, and you may have to either drain or suck out some of the existing fluid to do this). It contains solvents which will swell up the rubber seals which exist inside the transmission as well as on the outside, on some of the clutch drum piston actuators. One of your clutch piston seals is probably leaking, causing low mechanical pressure on that clutch which will make it slip (this creates an incredible amount of heat inside the clutch and will burn the clutch material as well as the fluid if you keep driving it this way, and then you'll KNOW what burnt ATF smells like!).

I had a '71 Ford station wagon with a C6, and for the last few years I had it, when cold it would not go into any forward gears until the fluid warmed up enough to cause the clutch piston seal to soften and make a tight fit to the bore, and then it would go into gear. In real cold weather, you might have to wait 2-3 minutes, but once it got warmed up, it was fine.

My hunch is that the same seal is the culprit in both your and my cases (my tranny rebuild books are at home so I can't recall exactly which seal is the problem, not that it matters--it's either on the forward or the direct clutch pack).

When you have got nothing to lose on a component (engine/trans), it costs you almost nothing to try the motor honey or magic additives. Otherwise I stay away from these products in general.

I'm not promising that this will work. The low fluid condition may have caused irreversible damage which no amount of magic additives will fix.

Posted: Thu Dec 13, 2007 6:04 pm
by asavage
The C6 is famous for slow engagement when cold. It's a common problem. And if that was the symptom, I'd go for the miracle-in-a-can treatment, which can last a few thousand miles before the softened seals trash themselves. The professional fix is to replace the seals (and clutches and thrust brgs while you're in there). The C6 is reputed to be very easy to overhaul, compared to others anyway.

But (almost) no drive in 'D' is probably not hydraulics in this transmission.

(I am not an expert, etc. etc.)

Posted: Thu Dec 13, 2007 9:06 pm
by rlaggren
Thanks for all your thoughts. Good link, Al.

I'm afraid I let the thing run low on ATF and caused damage, then put it under stress and something gave out. It quit all at once at the top of a steep hill and never "came back". Since it appears to have lost interest in all forward gears, somebody who knows could probably pin it on a part but I don't think it's a bad seal - more likely a trashed piston and bore. Looks like I've got a few months to ponder my sins before SOMETHING has to be done, so I guess I'll try the juice. Heck I entered Readers Digest Sweepstakes (once). <G>

I think Al probably has the best method - find a good used one and install it. The "find a good.." is the hard part.


Posted: Thu Dec 13, 2007 9:54 pm
by asavage
I have bought a lot of JY-class ATs (from JYs and from individuals) and knock-on-glue&sawdust, I've only had to pull one back out immediately. The rest have all worked.

While used parts are almost always a roll of the dice, the disparity in short-term cost between unknown used and rebuilt-with-warranty is enough to usually push me to roll the dice.

When I am working for someone else, I make them roll the dice, I just do the work.

Personally, I have had only two transmissions professionally rebuilt: in 1980, I had a Dual Coupling Hydromatic (not Hydramatic) in my '1959 Cadillac Eldorado Seville (yes, both) rebuilt by a shop in Phoenix. This is a 4-spd auto with a fluid clutch. It went in with only 1st & 3rd, came out with all four gears but funky shift points and shift feel. It never shifted as well as I'd like, but also did not fail on me while various stunts I pulled (hey: L is right next to R on those old Dual Couplings :evil:) took out three rear axles and cost me lots and lots of tires. I kept the oil clean and drove the snot out of it (Eldos in those days had factory dual exhaust and factory three dueces on the intake. Really.) But I never got the professional rebuild I thought I deserved. Cost was ~$6-800, I can't recall.

The second was the A4LD in the grey 1989 Aero. Bought the van with the trans in the backseat, disassembled and the case missing. Bought a core, took it all to Transmission X-Change in Portland, $1650 later (1999) I got a mild HD rebuild. It never worked right. Slow to engage manual L, whiny in 1st, and multiple extension housing bushing failures and rear seal leaks. About 15k after rebuild, the TC seal crapped suddenly (I mean within five miles it went from dry to leaking a cup a minute). Last year this time, the TC clutch grenaded (only 85k on the rebuild), so I rolled the dice and replaced it, flushed everything, got another four months from it before I lost the rest of the trans. It's in the attic now. I put a $150 CL trans in, it runs fine.

Based on those two, I think I have bad AT rebuilding karma. I have a fellow in Bremerton who does transmissions for a living, he doesn't get them right every time but always takes care of any problems, so I send him all the business I can. You ask enough folks, you'll find out who's not going to do a good job, and nobody in this county is any good, so I send all my business fifty miles away, and I appreciate knowing a good trans rebuilder.

Sorry if I got carried away . . .

For low-budget vehicles, ones that aren't needed to be ultra-reliable, a used trans, new oil & filter, and front & rear seal, will usually be the least expensive route to getting it back in service. This method only pays (IMO) if you do the R&R yourself. If you're paying someone else to do the work, think hard about those dice: can you afford to pay someone to do an R&R twice?

Because I work cheap for myself and expensive for others, I don't mind taking the chance so much. So far, I've been pretty lucky in the used AT arena. One way to look at it is that I'm overdue for a "correction": a rash of bad used ATs [shrug].

Posted: Sun Dec 16, 2007 9:54 pm
by rlaggren
Glad to hear there's some hope in the used market. I may try w/a used C6; it'll be a project for next summer unless the van stops creeping around the lot fast enough and a meter maid catches it. <g> If time and place don't work, I'll "donate" it. Once the other van is set up w/cabinets and get its various fixes, I hopefully I can zero in on the Maxima next month.

I can sympathize w/paying for services then finding stuff don't work right. Been there, almost always sorry. Like going to a restaraunt and finding out _for sure_ you could have had a better meal at home!

Thanks for all the thoughts.


Posted: Mon Dec 17, 2007 12:01 am
by kassim503
rlaggren wrote: it'll be a project for next summer unless the van stops creeping around the lot fast enough and a meter maid catches it
Is it in a parking lot and itll get impounded if it sticks around too long?

Posted: Mon Dec 17, 2007 8:09 pm
by rlaggren
> parking lot...

Yeah, that's it. It will creep around when it's cold and less willingly when it's hot. Enough to stay legal if not swish. <g>

Be interesting if I lose all the forward gears completely - have to develop a path in reverse that'll keep me out of dead ends and away from the neighbors. In the last 30 years, the only accidents I've had have all been while in reverse!