C6 QUESTION
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Laughing Gas
Joined: Feb 2011
Posts: 1,147
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From: Vine Grove KY
C6 QUESTION
Long time no talk fellers. How ya'll doing? Got a quick question. Im not a Auto tranny expert by any means, so here it goes.
I recently rebuilt the C6 in my truck along with an engine rebuild. I also replaced the u-joints in the driveshaft, and swapped a different axle in that had known good backlash between the ring and pinion gears. New tranny mounts and engine mounts also. Here is the question: Where is the play in my drive-line coming from? Can the play be coming from the C6? Or is it most likely the spider gear set in the diff? Its driving me crazy. It got a little better when I swapped axles and diffs, but not totally gone. Are 9inch rears known for getting slop in the spiders? Is it easy to replace the spiders? I had the diff out, cleaned it up over at Gary Lewis' place and checked the lash between gears. But I didn't check the spiders, or pay attention to how easy it would be to swap em out for new ones.
I recently rebuilt the C6 in my truck along with an engine rebuild. I also replaced the u-joints in the driveshaft, and swapped a different axle in that had known good backlash between the ring and pinion gears. New tranny mounts and engine mounts also. Here is the question: Where is the play in my drive-line coming from? Can the play be coming from the C6? Or is it most likely the spider gear set in the diff? Its driving me crazy. It got a little better when I swapped axles and diffs, but not totally gone. Are 9inch rears known for getting slop in the spiders? Is it easy to replace the spiders? I had the diff out, cleaned it up over at Gary Lewis' place and checked the lash between gears. But I didn't check the spiders, or pay attention to how easy it would be to swap em out for new ones.
Laughing Gas
Joined: Nov 2011
Posts: 1,033
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From: Wausau, WI
First of all, what symptoms are you having? Is it clunking when you put it in gear? A clunk when going from throttle to coast (or vise verse) when driving?
The spiders are wearable parts too. I have never personally had a set get sloppy on me, but have heard of it from others. A way to check them (of it's an open rear) is to jack up the rear, unhook the driveshaft (that will take everything else out of the equation), and rotate one tire forward and back. Just do it enough to be able to feel any play, it shouldn't take much movement.
If it's a trac-loc, that will be a lot harder to check as the clutches will be fighting you.
The easiest way to replace them if bad is to pull the carrier out of the third member. But then you need to re-set your lash in the spiders and the ring and pinion.
Another thing may be pinion bearings. Check for any movement of the pinion by trying to move it in all directions. There should be no play in the pinion at all.
The spiders are wearable parts too. I have never personally had a set get sloppy on me, but have heard of it from others. A way to check them (of it's an open rear) is to jack up the rear, unhook the driveshaft (that will take everything else out of the equation), and rotate one tire forward and back. Just do it enough to be able to feel any play, it shouldn't take much movement.
If it's a trac-loc, that will be a lot harder to check as the clutches will be fighting you.
The easiest way to replace them if bad is to pull the carrier out of the third member. But then you need to re-set your lash in the spiders and the ring and pinion.
Another thing may be pinion bearings. Check for any movement of the pinion by trying to move it in all directions. There should be no play in the pinion at all.
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Laughing Gas
Joined: Feb 2011
Posts: 1,147
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From: Vine Grove KY
81 and Gary,
Its a clunk when throttling from a coast or engine braking from throttling. Its not noticeable at low speeds. Only in third gear on the freeway....Im thinking something in the tranny is worn out?
Its a clunk when throttling from a coast or engine braking from throttling. Its not noticeable at low speeds. Only in third gear on the freeway....Im thinking something in the tranny is worn out?
Moderator
Joined: Jan 2001
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From: Virginia
All you have to do is jack up the rear of the truck, leave the tranny in park, and wiggle the driveshaft and the tires and see how much play is there. If there is none, I would check the bolts on the torque converter/flexplate to make sure they are tight.
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Laughing Gas
Joined: Feb 2011
Posts: 1,147
Likes: 6
From: Vine Grove KY
Gary, yes me and you put new u-joints in it about a year ago. We checked the pinion gear to ring gear lash after thoroughly cleaning the diff of oil and we got .012" lash, which is on the loose side of tolerance (.008"-.012" lash).
We also put new axle bearings in the housing at the FTE OK Chapter GTG. The pinion bearing seemed fine to me at that time.
If its the tranny, what in the tranny would cause it to have slack?
Thanks alot guys.
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Joined: Jan 2001
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From: Virginia
I have never heard of the tranny having a problem causing driveline clunking. That doesn't mean it can't happen, but if it was possible it would be pretty rare.
Now that I think about it more, a good test would possibly be to leave the rear of the truck on the ground, chock the wheels so the truck will not roll(or set the parking too) and put the tranny in neutral. Then get under there and twist the driveshaft back and forth.
You will get some play of course, but I would think the driveshaft will turn less than a 1/4 of a turn before it catches.
Now that I think about it more, a good test would possibly be to leave the rear of the truck on the ground, chock the wheels so the truck will not roll(or set the parking too) and put the tranny in neutral. Then get under there and twist the driveshaft back and forth.
You will get some play of course, but I would think the driveshaft will turn less than a 1/4 of a turn before it catches.
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Joined: Jul 2010
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From: Northeast, OK
That would test the diff, but not the transmission. But since the tranny isn't going to be in gear when stopped, I don't see a way of testing it - especially 3rd gear where the thunk is.
As said, I have heard clunks from all my Ford trucks over the years - even in my 72 when it was new. I have often wondered if the long, hollow driveshaft contributes to that by ringing. Anyway, If you have wear in the splines on the axles and the splines where the driveshaft goes into the tranny plus max backlash in the diff that may be par for the course.
As said, I have heard clunks from all my Ford trucks over the years - even in my 72 when it was new. I have often wondered if the long, hollow driveshaft contributes to that by ringing. Anyway, If you have wear in the splines on the axles and the splines where the driveshaft goes into the tranny plus max backlash in the diff that may be par for the course.
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Laughing Gas
Joined: Feb 2011
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From: Vine Grove KY
Its not as audible as it is physical. This tranny was the original tranny that I had Hi-Tech transmission in Tulsa rebuild. It was a $600 rebuild so maybe there are some 3rd gear components that didn't get spec'd or replaced. I will test the diff by franklin's suggestion but I will just drop the driveshaft and feel the play by the yoke, that way I can leave the tranny in gear and twist the driveshaft to see if I get any odd play. Of course that would only tell me if 1st gear had play, but at least I would rule it out.
Cargo Master
Joined: Aug 2007
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From: New Zealand
Does it act the same going into reverse, as it does into drive?
I had one C6 that engaged reverse pretty hard, but was normal going into any forward gear.
I'm not an auto trans guru, but reverse oil pressures are double that of the forward gears, & there is a valve that temporarily reduces that pressure as you engage reverse.
In my case that valve was not operating properly, giving the hard reverse engagment.
I was lucky - a bottle of Lubegard fixed the problem (slowly over a few months)
I had one C6 that engaged reverse pretty hard, but was normal going into any forward gear.
I'm not an auto trans guru, but reverse oil pressures are double that of the forward gears, & there is a valve that temporarily reduces that pressure as you engage reverse.
In my case that valve was not operating properly, giving the hard reverse engagment.
I was lucky - a bottle of Lubegard fixed the problem (slowly over a few months)
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,707
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From: SE Florida
Your lash is almost certainly in the axle. I can't think of a way the transmission can do this.
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Laughing Gas
Joined: Feb 2011
Posts: 1,147
Likes: 6
From: Vine Grove KY
No, that's not it. In third gear there are no gears in play. The clutches lock all the rotating parts so that they rotate as one unit.
The C6, like all automatic transmissions, default to neutral when the pump is not spinning.
Your lash is almost certainly in the axle. I can't think of a way the transmission can do this.
The C6, like all automatic transmissions, default to neutral when the pump is not spinning.
Your lash is almost certainly in the axle. I can't think of a way the transmission can do this.
So that leaves
1. Spider gears
2. Ring and Pinion Lash
3. Pinion Bearing
4. Wear on the axle splines
or any combination of the four.
Sounds to me like I need to take the spare third member I have sitting in the garage and have someone rebuild it. If that doesn't fix it, im rollin' it off a hill or tradin it for a coupe deville.......just kiddin.