Good morning everyone. New to the forum and new to Y blocks, Fordomatics and 55 Tbird. My little car appears to be 95% original and since it's that way I would like to maintain everything I possibly can. However, the transmission doesn't seem to go into high (if I have the correct understanding of the basic transmission function). I can select Lo or Dr, the car shifts between them fine manually. What I don't feel is a shift from intermediate (which is where I think the car starts out while Dr is selected) to Hi. Is this a possible problem with bands, servo, or something else entirely? Are these transmissions reliable after a rebuild, or should I just go with C4? I have some engine questions too. I think I'll make a different post for them. 
Thank you in advance for any help.
JH

There is a Diagnostic Sequence to run through on the FORD AT SHOP MANUAL for the appropriate year.  

Yes, it is rebuild-able if needed and you want to keep the car origional ($$$).

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Thanks for your reply KULTULZ.
Does the diagnostics need to be performed while still in the car? I've already pulled it. 

"Does the diagnostics need to be performed while still in the car? I've already pulled it"

You're a tough man. Did you have to pull the engine?

There is a diagnostic sequence using air pressure via a valve body adapter but if you have it on the bench, you should consider overhaul now and be done with it (IMO) Parts (other than some hard are readily available).

Don't forget that this is a mechanical adj trans (THROTTLE VALVE - MECHANICAL LINKAGE) so you need the Bible (IMO).

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Thanks again Kultulz
(You're a tough man. Did you have to pull the engine?)
Yes,pulled engine too. I don't see any other way. Maybe slide engine forward, but what's the point in that. lol
 

There is a diagnostic sequence using air pressure via a valve body adapter but if you have it on the bench, you should consider overhaul now and be done with it (IMO) Parts (other than some hard are readily available).
I downloaded a manual a little bit ago (1955 Fordomatic Shop Manual) and I'm not enjoying what I'm reading. I suppose I'll take it to my transmission guy (although he's down to part time work and only working on things he likes.) 

Too bad your not closer. I have one I just removed from a 56.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Two things come to mind, kick down linkage throttle pressure rod too long or the governor not working.

Thanks Sandbird,
The kickdown linkage seemed right to me. (moved as the throttle linkage moved) 
But I'm now having regrets about taking it out and not fully investigating all external factors. (shifter included)
The car had sat for so long my knee jerk reaction was to remove it and rebuild it. But I'll make sure those things are correct when it goes back in.

What RPM does your tack say at 60 mph.

Look at the bright side. With the engine and trans out, it’s much easier to clean everything up. If it’s still got the road draft tube, have a go at the frame and x member. Even though mine was an older restoration with few miles there was plenty of oil residue there.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ