[rockyrivermark]

1967 mustang
289 C4

Was getting a later shift form 2-3 when cold and then lost 3 all together. But was still driving fine in 1,2 gears.
New Fluid and level correct

Installed new modulator and adjusted the bands
Screwed in band bolt to 10ft/lbs then backed off 1 3/4” turns on drivers fronts and 3 turns on passenger rear.
now it will go into gear for a second or two and pop out
same thing for reverse.
Any suggestions?

 

[Blues Power]

hmmm, id take it to a shop. they did wonders for FMX
way better than me fiddling with it for 3 months

 

[rockyrivermark]

Nope. I’m not a take it to a shop guy. Did the restoration on this and 2 others all DIY.
I may have to pull it and rebuild but was hoping for tips on things to try before I do that.
thanks though.

 

[Grimbrand]

Nope. I’m not a take it to a shop guy. Did the restoration on this and 2 others all DIY.
I may have to pull it and rebuild but was hoping for tips on things to try before I do that.
thanks though.

When I lost 3rd it was due to a planetary gear coming apart.

 

[Hemikiller]

First step would be to ensure your vacuum modulator is receiving a good vacuum signal.

3rd and reverse are controlled by the Reverse/High clutch. If 3rd engages and falls out, it may be the seal on the piston is leaking. If reverse is doing the same thing, then it's most likely rebuild time.

 

[rockyrivermark]

Roger that. Thanks
Oddly it was driving ok (minus no 3rd) before the new modulator and band adjustment. I’m going to swap in the old modulator just to see if the new one is bad. Box looked old from Napa so who knows.
Then I’ll drop it for a rebuild.

 

[rockyrivermark]

First step would be to ensure your vacuum modulator is receiving a good vacuum signal.

3rd and reverse are controlled by the Reverse/High clutch. If 3rd engages and falls out, it may be the seal on the piston is leaking. If reverse is doing the same thing, then it's most likely rebuild time.

Yes. That was the first thing I check. 21 inches of vacuum

 

[rockyrivermark]

Update:
Fluid level was fine when I drained the pan to swap out the modukatkr and I put that same fluid back in. Checked when hot and in park.
somehow it was low on fluid. Topped it off and it’s drivable again but still missing 3rd gear.
the rear passenger side band was way out of adjustment and possibly the reason I lost third? I did snell burning snell for a second or two before I lost 3rd the other day.
I’ll drop it and give it a rebuild next weekend. I’ll throw a shift kit in it while it’s out.
Being that this car hasn’t been on the road in 35 years I’m expecting some issues to sort out.
thanks for the info as always here

 

[Ronstang1966]

I bought my Hertz Shelby missing 3rd gear. Drove it home slow, dropped the transmission and there was no damage to any hard parts. Did a full rebuild since it was apart and it drove like a champ. It is a seal issue. Don't bother trying to find which just rebuild the whole thing. While your in there spend the extra money on new bushings and thrust washers etc. and do it right. You won't be sorry. These transmissions are super easy to rebuild. You can even do a bunch of the old school C-4 mods while in there like drilling the direct clutch drum for faster fluid release for a really stout transmission. Depending upon which direct clutch drum you have there may be an extra snap ring slot which allows for an extra steel and an extra clutch. I used to get these drums at the core place for a few dollars....sort through a pile until I found the ones I wanted, now you can buy them online for $400 plus .

 

[rockyrivermark]

I bought my Hertz Shelby missing 3rd gear. Drove it home slow, dropped the transmission and there was no damage to any hard parts. Did a full rebuild since it was apart and it drove like a champ. It is a seal issue. Don't bother trying to find which just rebuild the whole thing. While your in there spend the extra money on new bushings and thrust washers etc. and do it right. You won't be sorry. These transmissions are super easy to rebuild. You can even do a bunch of the old school C-4 mods while in there like drilling the direct clutch drum for faster fluid release for a really stout transmission. Depending upon which direct clutch drum you have there may be an extra snap ring slot which allows for an extra steel and an extra clutch. I used to get these drums at the core place for a few dollars....sort through a pile until I found the ones I wanted, now you can buy them online for $400 plus .

Cool. Thanks for that info. I had third gear for a week and then right after I smelled some burning it was lost. got the rebuild kit and going to do it this weekend.
i rebuilt a C4 in my ‘67 cougar. Want bad. I didn’t dig all the way into the entire unit though.
clutches, bands and valve body was really dirty.