727 TF no 3rd after its warm

[vick79]

Hi Guys, I recently got my charger back on the road. I did a fluid filter change, and replaced a trans fluid cooling line that got pinched, also FYI had to mess with kickdown cable, linkages when I did a ton of other work on carb, headers etc. When its cold I have all 3 gears, after I drive about 10 miles I loose 3rd, it just will not engage. Once its cold, 3rd is back.

Need some guidance if it could be a linkage issue, cooling/overheat or just means im going to need a rebuild?

[John_Kunkel]

3rd gear is the front clutch; probably a sealing issue is causing pressure leakage that prevents the clutch from engaging when the fluid warms up and thins out.

[Kern Dog]

I've had 2 cars that acted the opposite. When they are cold, they wont UPshift to 3rd. They have to warm up to go into 3rd. Manual shifting or tapping the throttle makes no difference either.

[ACUDANUT]

Sounds like a Linkage issue. IMO

[Kern Dog]

Linkage? Why would you think that? The linkage doesn't change at any time during the operation of the vehicle?
Fluid cold.....Linkage is the same
Fluid warm...Linkage is the same
Fluid hot......Linkage is the same
Fluid low......Linkage is the same
Fluid normal..Linkage is the same
Fluid high.....Linkage is the same
Wrong fluid..Linkage is the same
Burnt fluid...Linkage is the same

[ACUDANUT]

The linkage under the car can slip. The adjuster bolt can come loose. 
Just one possibility.

[vick79]

I took the linkages apart when I had to change header and starter, everything is back on tight, very certain.

Does the throttle pressure linkage/kickdown affect 2-3 shift? It was mounted up all wrong when I got the car.

Right when it gets hot, it "tries" to shift but RPMs just rise as if its in neutral.

[ACUDANUT]

Last guess, try to adjust the transmission kickdown

[469 runner]

I agree with Mr Kunkel on this one...seen it happen many times.  Fluid gets warm and 3rd goes away.  Either metal sealing rings are worn, or the rubber O-rings that seal the front clutch piston are getting hardened.  Possibly a bottle of transmission seal conditioner would get a few more miles out of it.  Either way, the front clutch is probably leaking.

[469 runner]

Another check you can try.  After transmission is warm and not shifting into third.  Park on a hill facing down (make sure there is no traffic), then put into reverse and try backing up at a brisk pace.  If you feel the transmission slipping then you'll know for sure that your front clutch is toast as this clutch is engaged for both 3rd and reverse.

[ACUDANUT]

Wow, I never heard that. 

[John_Kunkel]

The front clutch is also used in Reverse but sometimes when 3rd goes away Reverse works OK because the line pressure is about 3 times higher in Reverse. Like runner suggested, putting an extra load on Reverse will sometimes show slippage.

[vick79]

Very informative advice I will give this a try tomorrow!! Now that you mention it, when its cold, I have to give it a fair amount of throttle to get it moving in Reverse. Almost seems like I have the parking brake set while moving it...

[John_Kunkel]

Sluggish transmission behavior when the car is first started is kinda normal if the car is started in Park and then shifted to a gear, it's due to converter drainback...try starting the car in Neutral instead of Park, that will refill the converter immediately.

[ACUDANUT]

Me too, but I thought everyone knew that