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Discussion Starter · #1 ·
Just pulled the trans apart. Everything in the trans looks great except the directs which are fried. I usually get a good two years out of a freshen up but only got one year this time. Maybe a 1000 street miles and a dozen drag passes.
Trans info: C5 case, pro brake VB (not sure brand), rollerised in all spots that don't require machine work, 6 clutches in both drums, 8" 5500 Coan converter.
Last time I freshened I checked pressure. 1500rpm was about 160psi and 2500rpm was about 205-210psi.
I think clutch clearance was .048"
Clutches too tight?
I do still need to drill the bleed holes in the direct drum.
Any thoughts? A pic of the damage..
Automotive tire Food Tread Gas Ingredient
 

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They're certainly shagged :( . That clearance is ok for 6 frictions. Were they red frictions like the forwards?
What RPM you turning in 1st gear? Definitely needs a bleed IMO
Forwards look ok, pressure is good . What does the band look like ? Sealing rings ? A tie up on the 2-3 shift maybe ? Was it a HARD shift? There's something going on there that is way worse than normal wear needs sorting out
 

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Discussion Starter · #3 ·
These were the raybestos gen 2 blues. The reds in the forward look like the day I put them in. Both bands/drums look great. Teflon rings still in good shape.
Both 1-2 and 2-3 have always hit hard on this trans.
I did 2 transbrake/bump box tests back to back. I was closely watching my temps. Before the tests I was about 160 and after the tests the gauge showed 215. Hot but not "destroy stuff" hot. I then drove normally for about 3-4 miles and temp came down to 190.
The next day I took it out for a drive and it was slipping in 1st and 2-3 flairing with anything other than light driving.
Upgraded from the reds to the blues because I thought they were better but don't think it is the clutches fault.
 

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Get a pressure gauge on there . Seems odd you feel a slip in 1st yet forward clutches don't show anything.
If all sealing rings and clutch seals test ok time to look into the valvebody. Need to find what caused those clutches to destroy themselves , definitely not a clutch fault
Something in the valvebody allowing that clutch to hold partially on maybe ? Trace the circuit back to see how that clutch exhausts ...
Even if there was centrifugal apply that bad to destroy clutches you'd feel it binding up in 1st gear , a bleed would help but if it was only that i'd expect to see heat or hot spots there only . The 2-3 flare cause is obvious.

Assuming band is ok. What intermediate servo ? any mods ? Hole in case plugged ?
 

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'72 Ltd brougham 4dr.
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I know they're of a somewhat different design, but I seem to remember a similar situation brought up while researching for a C6 rebuild a short while ago; something about band release vs clutch apply timing? Can't recollect the details off hand at this moment but the source was Precision Transmission; a guy out of Texas w/ 40+ yrs.Has a series of teardown/ diagnosis videos on YouTube w/ his family business that I found very informative.
Maybe give it it a look. Good luck bud
 

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That's an interesting servo . The large area runs in the case ? It looks like that apply area is larger than a "C" servo. What diameter is the outer apply section?

If there was a tie up on the shift I would of expected to see the intermediate band damaged.

That pump gear looks to be old wear , that's how they go with age

So was anything changed last freshen up ? Seems odd was ok previous but this time hasn't lasted . What were those frictions like on any previous freshen?

At this point it kind of looks like valvebody, maybe slow release on the brake ? Dragging those frictions . What is the valvebody as in make ? External solenoid ? Is there any check or adjustment required on that valve for transbrake release?
 

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Discussion Starter · #13 ·
I know they're of a somewhat different design, but I seem to remember a similar situation brought up while researching for a C6 rebuild a short while ago; something about band release vs clutch apply timing? Can't recollect the details off hand at this moment but the source was Precision Transmission; a guy out of Texas w/ 40+ yrs.Has a series of teardown/ diagnosis videos on YouTube w/ his family business that I found very informative.
Maybe give it it a look. Good luck bud
I have seen the videos you are talking about. I think he is in Amarillo, about 4hrs north of me. He does seem to be good at what he does.
 

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Discussion Starter · #14 ·
That's an interesting servo . The large area runs in the case ? It looks like that apply area is larger than a "C" servo. What diameter is the outer apply section?

If there was a tie up on the shift I would of expected to see the intermediate band damaged.

That pump gear looks to be old wear , that's how they go with age

So was anything changed last freshen up ? Seems odd was ok previous but this time hasn't lasted . What were those frictions like on any previous freshen?

At this point it kind of looks like valvebody, maybe slow release on the brake ? Dragging those frictions . What is the valvebody as in make ? External solenoid ? Is there any check or adjustment required on that valve for transbrake release?
The servo looks like a PA servo with the logo sanded off. I will get the diameter.
Only change on last build was new clutches (change to blues) and steels. Reused forward clutches, bands as they looked great.
I don't know the make of the VB. It does use an external solenoid with no adjustment that I am aware of.
This is what the directs looked like on the previous freshen up after about 2yrs of use.
 

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Those clutches from last time are fairly normal . Something has changed this time . I don't think it is just the clutches

Not also in that last pic your selector lever is fitted wrong. It is pushed on too far and only 1/2 clamping on the selector shaft ;)
 
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