727 question

Well today the first day at the track for the year 2nd gear was not there. It did not flare up like it was slipping, it just seemed to still be in first and went on the limiter.I went through my trans over the winter. Put in a supersprag, new soild red front band. New clutches and thrust washers. Griner brake, releases OK, 1st, rev and High gear are all fine. I checked the band and the adj was still about 1 3/4 turns. Same case, and brake as last year. I thought if 2nd was broke the engine would rev like it was neutral. Does it sound like a servo sealing problem? When I drive in the pits and shift it seems to shift after 10-15 seconds. Any experience like this before? This is not my first 727, but my first to have a problem immediately after going through it. Sorry for the length of the post, but want to know the best place to look first.

Here is some thinking out loud to hopefully trigger the answer.

In a TF transmission, the only difference between 1st and 2nd is the front band stopping the front drum. Plus, if you have 1st gear band apply, it lets go so the rear drum can spin (say CW). The sprag stops it from turning the other way (say CCW). So either the band is not stopping the front drum, or the rear band is not releasing (if you have LBA).

But I am thinking the rear band is releasing since you say it is like it isn't shifting at all, ie front band is not stopping the front drum. That points to a front servo issue. I was thinking a band strut bent or the ears on the band broke, but you said the adjustment is still the same, so that rules that out.

The good news is that you can do a lot to check that without pulling the trans out of the car. But you will have to remove the valve body (it could be the problem too). After pulling the valve body, put air pressure with a rubber tipped gun on the hole that pressurizes the front servo and see if the action tightens the band and listen for excesses leakage.

I do this "dry" when I build the trans, just lube on the rings. But after circulating fluid, be ready for a shower of fluid. Some leakage is normal. I will look for a pic to show which hole to pressurize.

EDIT: This attachment has the port labelled, "Front Servo Apply"

Make sure the linkage is set right. If that's not the cause, check the KD band apply servo. Might also be the band going south.

Since it is a manual VB, It could be something in the factory governor circuit. Some VB's looped the supply and return together to make the VB shift on demand. Check for internal fluid leaks. I once had a VB that would shift correctly and it was just one of the endplates was loose. Another thing it may be is sometimes a checkball may peen its way through the seperator plate. I had this happen before and I think it didn't shift into second.

Thanks for all the relpies. The response to put air pressure on the servo apply port helped me identify my problem. The kickdown band I put in over the winter was slightly larger than my previous one. When the band is clamped the ends tough before enough force is applied to stop the drum under power. I attached a photo. The Alum front drum has some runs, but is not worn much. It must be slightly smaller diameter than a stock one. I would have never thought to check this when assembling the trans. At least now I know what to fis, and the servo was sealing fine.