C6 reseal

[cjarvis]

Morning all...

Hoping you guys can steer me right on my leaking C6. Its leaking from the front pump and the shift rod. See pix. The oil in the bell housing has accumulated since Saturday.

Trans is out of a 71 CS with 38K miles (12K in the last 5 years), so I am thinking just replace the bad seals rather than rebuild. Also thinking of doing it myself. Auto trans is about the only thing I've never done on a car/truck. But I am worried about the learning curve to take it apart and put it back together. Any suggestions on re-seal vs rebuild? DIY vs hire it done?

Thanks in advance for any advice!
Craig

[fordman]

The front can just be poped out and replaced. he shaft seal requires pulling the pan and shift shaft to replace the rubber o ring. Be sure to note where and now the shaft is pisitioned. And ti put it hack exactly as noted.

[cjarvis]

Thanks fordman... Do you have a preferred source for C6 parts? Several come up in google search, and then there is ebay.

[fordman]

The local parts store is where i would go for those small parts. For just such a small order why pay shipping.

[cjarvis]

So my original intent was to fix the leaks at the front pump and the shift rod, and I think I can see my way to getting that taken care of (thank you foreman). All the reading I've been doing on the C6 has me thinking about a few other problems.

One is no down shift on WOT, the other is a bit of a thump in the drive train when pulling away from a light. I replaced the vacuum modulator, adjusted the screw in, verified vacuum was there (well my thumb over the line told me there was vacuum there), but still no down shift. Haven't done anything on the thump, I assumed it was the rear diff and lived with it. So the reading I've done has me thinking torque converter for the thump, and maybe the downshift too. Maybe related, with the engine tuned to spec (idle, timing, dwell) the truck will stall when I come to a light. The harder I brake to a stop, the more likely it will stall. I adjusted the idle up some to deal with this a bit. But the reading I've done has me thinking torque converter could be contributing to this too. Low vacuum (tired motor) could explain the downshift and stalling at lights. I've discounted that because the truck has 38K on it. But thats 12K in the last 5 years and zero the previous 30 years or so. I wish I had put a vacuum gauge on it before pulling the trans. Anyway, the governor on the output shaft is fine, pistons move free. Pulled the front pump and it looks great. Both bushings the pump ride on look new. Everything inside the trans is pretty pristine. So I don't know whether to replace the torque converter along with the seals. Gonna do the servo piston too, its cheap and easy.

So I guess the question is: what is the likelihood the torque converter in behind the thump? the no downshift? the stall at idle? Good idea to replace TC too? or waste of money?

Thanks again for the help!
Craig in MI

[BobbyFord]

No downshift at WOT is because you do not have the kickdown rod hooked up between the trans and carb and the kickdown lever is missing from the side of your transmission.

[cjarvis]

No downshift at WOT is because you do not have the kickdown rod hooked up between the trans and carb and the kickdown lever is missing from the side of your transmission.

No, it's there, just hanging waiting for the trans to come back. I pulled the lever off the shaft when I pulled the trans, so thats why its missing from the pic above. And it was adjusted too, so that pedal to floor moved the lever on the trans to its full stop, and still no downshift.

[BobbyFord]

...No, it's there, just hanging waiting for the trans to come back. I pulled the lever off the shaft when I pulled the trans, so thats why its missing from the pic above. And it was adjusted too, so that pedal to floor moved the lever on the trans to its full stop, and still no downshift.

It's possible that the lever in the trans is not in the correct spot. Someone could've had the valve body out and didn't get the lever correctly engaged.
You'll find out when you drop the valve body to replace the selector shaft seal.

[cjarvis]

It's possible that the lever in the trans is not in the correct spot. Someone could've had the valve body out and didn't get the lever correctly engaged.
You'll find out when you drop the valve body to replace the selector shaft seal.

Shoot. I had already dropped the valve body, so can't say for sure. The plunger the lever presses on moves fine. Guess I'll have watch when the valve body goes back in to make sure it works right. Thanks for the heads-up.

[fordman]

Syallimg at stop light is a accelorator pump in the carb symptom.

Have you checked u joints for slack. To find thump.

[1972hiboy]

Yeah I dunno if a c6 torque converter has the ability to grab an engine hard enough to stall it. Ive only seen torque converter/ stall at stoplight situation happen with a torque converter that has lockup capability. Im wondering if its a engine tune issue and it becomes more pronounced with a little bit of drag on the engine from the torque converter? I mean what is a c6 torque converter? One turbine , one fan, and fluid. If the TC was damaged and was indeed grabbing the engine im sure if would be trying to push you forward in drive.

[cjarvis]

Thanks for all the feedback.

On u-joints, that was the first thing checked on the thump issue. They are tight. I read recently that the spline coupling in the driveshaft can be the source of a thump in Ford trucks. Skeptical on that as I've pumped a ton of grease into that zerk fitting, and it feels more like a slip than clunk.

On the accelerator pump and the stall issue, the stall occurs when throttle is closed and braking, rather than pulling away from a light. As the truck comes to a stop, the R's have fallen so low it sometimes stalls. My understanding (possibly wrong) is that access pump shoots gas in as the throttle snaps open to avoid a brief lean until the jets catch up.

On the torque converter, I read somewhere that it can affect fluid pressure. My money on the thump right now is that its a fluid pressure issue. RPMs at a light can drop to 600 or so, fluid pressure drops, hit the gas and it takes a second for pressure to develop, and when it does the thump happens. I could be smokin' something with that theory. But I thought the TC could be the culprit. More reading says it might be the valve body or the booster valve in the throttle body. Its seems to be something a C6 shift correction kit might solve. So I am thinking now that it's probably not the TC (as 72HIGHBOY is saying). Going to try the shift correction kit and boost valve and see what happens.

So I have have a gasket and seal kit to fix the leaks, ordering a shift kit to hopefully fix the thump, and hopefully the downshift issue. Plan to use the original TC and not replace it.

But now curiosity has kicked in, and I've pulled more apart to look for worn parts. The outer pump bushing is worn, stator bushing shows a little wear. Other bushings look great. So I'll replace those two. Friction plates I've pulled so far look pretty good. I haven't pulled the reverse clutch yet. Give the condition of the first two clutches, i's expect the reverse clutch to be fine. Probably should pull it out to be sure. But I'm questioning whether I should replace the friction plates while I'm in here. Any suggestions? I'm leaning toward just replacing them, maybe with the Red Raybestos HDs. Anything else I should be thinking about? Pics below.
Thanks for the help!

Pump bushing:

IMG_0622.jpg

Direct drive friction plate:

IMG_0627.jpg

Front clutch friction plate:

IMG_0628.jpg

[fordman]

Stalling when braking coyld be a vaccum leak in the brake booster.

[cjarvis]

Thanks for all the help on my C6. I thought I'd post a follow up now that its been on the road for a while.

Original problem was a leak at the front pump and the gear shift rod. Also thought that a drivetrain thump pulling away from lights and stalling while approaching lights could be related. Trans would not kick-down either. 39K on the truck.

Once the front pump was off, curiosity took over. I ended up going all the way even though clutches looked new, and only a few bushings showed any wear. One thrush washer had wear. One of the original thrust washers was nylon, and I didn't like the idea of putting a 44 year old nylon part back in. So I replaced all fricton plates and steels, bushings, thrust washers, torque converter, and installed shift kit. Used Red Raybestos HP Stage 1 clutches and Kolene Steel plates, Kevlar band, Super heavy duty Allison spec torque converter (1300 stall), TransGo shift kit, Transtec gaskets and seals, vacuum modulator, servo piston, filter, and new pan.

This was essential: http://www.oreillyauto.com/site/c/detai ... &ppt=C0196

So driveline thump is gone, stalling at lights is gone, no leaks. One bushing on the kick down rod disappeared and I couldn't get it to work smoothly, so I left it off for now. Will add a kick down cable in it place. Driveline definitely seems tighter, but that could just be the lower stall TC.

Thanks again for the help!