1977, c4 transmission no forward gears

[21drivers]

I just bought a 1977 thunderbird for $1200. Amazing deal. No rust, body damage, etc.
The catch is that the c4 transmission has no forward gears, and the engine is in need of main bearings, rings, and maybe an oil pump (oil light is on at idle) but it does run right now.
I'm expecting to have to pull the transmission, but I'm curious what causes the forward gears to go out? It needs to be rebuilt (probably), but what actually goes wrong to cause this?
It still has reverse.

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[74 Harley]

It could be bad clutches, broken bands, planetary gears, the list goes on.
Good luck with your project, keep us updated with pictures!

 

[mcm51]

I can't help much on the tranny, could be all kind of stuff, and I've seen through the years, no forward gears but reverse works....From your photo, it looks like you got a great project car to start, I like that color, side molding looks good, front grill looks good, front bumper maybe tilted down a tad but in great shape, this Bird would look great with the locking spoke hubcaps, if you can find them........You did'nt mention if it was a 351 or 400 ? auto on floor or column..........Keep us up on how things go...............

 

[21drivers]

It's actually a 302, c4 (auto) and column shift. Is it unusual for it to be a 302?
There's really no telling exactly what's wrong until I get the transmission out, just wanted to see if anyone wanted to place bets lol.
I checked the fluid and there is definitely a burnt smell, with some clutch material.
Ill probably have it out before my next update

 

[mcm51]

I had a '78 with the 351 and floor shift auto, regret today ever getting rid of it, it was white with brown roof and trim, stripped inside just a/c, am/fm radio and crank windows, most of those '78-'79 or about 60% had a 351, 30% 302, 10% 400........
Burnt smell and shavings, been trying not to say but your gonna have to drop it, have a shop rebuilt it, put it back in......
Still want to say ya got a nice clean 49 y/o Bird to start working on there, that '78-'79 in decent shape are getting real hard to find....

 

[21drivers]

Update
Got the transmission out and mostly torn down. I'm going to try and rebuild it myself at home.
I found the cause, so thats nice. The forward clutch pack is completely fried!!
Zero material left.


Forward on the right, reverse on the left


I also found all of the clutch material behind what I believe was the forward piston

I love when the issue is so obvious. No guesswork.
I decided I was going to leave the motor in to rebuild later as it's running, but after investigating further, I'll have to pull it out and do it now.
The rear main is so bad that oil pours out upon removing the flex plate bolt.
A full, steady stream of oil.
View attachment 36254


It will be the second engine rebuild I've done, and now I'll get to say I rebuilt a transmission, too.
Got any pictures of your old 78' mcm51?

 

[21drivers]

The engine and transmission are now rebuilt. It wasn't too hard, actually. It's running pretty good (timing could use adjusting) and the transmission shifts decent, with the exception of the kickdown needing adjustment.


The bearings were definitely smoked, so the rebuild was necessary.
Driven about 10 miles so far, no oil leaks (trans, rear main, etc.)


Obviously I'm still breaking in the piston rings but the camshaft is already worn in.

Few things I've learned:
351 power steering pump works on a 302
Reverse C4 drum from a 1965-69 will fit 1977
Engine rebuilds can be fun
Thunderbirds are really comfy

 

[biddle]

Good job! It's crazy, back when I was in the car business, in the early 1990s, if someone tried to trade in a nice running, nice big 1970s car, they would appraise it at $0. haha You could not give them away back then. I bet a lot were crushed.