Looking for some advice before taking the transmission out of the car...

Transmission was rebuilt back in the days in 1998 (by me) with a B&M shiftkit/rebuild kit. In 2014 I changed the VB to a Cheetah auto, otherwise working fine on the street during all these years.
But now after almost 25 years and >40 tmiles it has started to slip in 2-3 upshift when hot and on a really hot day not shifting at all to 3rd. When cold everything works ok, not crisp 2-3 upshift but still hard.
When the oil gets hotter the 2-3 upshift goes weaker until almost gone. Reverse is fine, but when hot more soft shift when engaging.
Have not had any leaks and when checking the fluid it seems ok, not smelling and level also correct.
downshifts are ok, both low speed and kd WOT.

I had a little time the other day so I put 3 hydraulic pressure gauges on the transmission and my -68 Charger up on jack stands, to check line pressure, front and rear servo pressure. But for some unknown reason I could not get any readings from the line pressure and front servo, only rear servo was showing. I tested the two 100PSI gauges with air compressor and then they showed pressure, so I do not understand why they showed 0 while testing the transmission.
So only readings I have for the moment is the rear servo.
In L it was between 60-90+ PSI (idle / throttle pressure max), seems ok, and steady readings. In R it was from 90-240 PSI (idle / 2000rpm), but really shaky on the high mark (220-250psi).
I will try once more with another gauge on the line pressure to see if I can get some readings.

So what do you think ? Some sealing failing when oil hot ? Or has the front clutch been working overtime too long already, so a total rebuild to be done.
Is there anything more that I could investigate while transmission still in car ? It is always more fun to repair when knowing what the actual fault was.

How long do a 727 live on the streets between rebuilds on 3-400 HP cars ? I thought 40t+ miles were a little too early anyhow behind a mild 360 smallblock.

Were you able to achieve all gears on the jack stands or only L and R?

Front servo should only show in third gear.
Line pressure (middle tap on pass. side of trans) should be seen in all forward gears and neutral.

Fluttering R pressure coupled with your complaint could mean worn reaction shaft seals (metal).
Or worn high clutch seals ( in the front drum ).

Your 3rd gear problem does sound like pressure leakage as the fluid gets hotter and thinner, piston seals or sealing rings.

The lack of a pressure reading at the accumulator while showing pressure elsewhere is mystifying.

The shaky gauge readings in R are probably due to the over-pressure relief valve (used after early '68) especially when modified by the B&M kit. It relieves pressure and then resets causing the needle to be unsteady.

Yes I was able to get all gears on the jack stands.
And the missing line pressure and front servo readings has to be faulty test gauges, even if they both were brand new out of the box

Yesterday I tried another gauge that I had in the garage, and then I did get readings on the front servo, 50-75 PSI in 3rd gear idle/ TP (throttle pressure was not maxed out, gauge was only 0-80psi)

So now it's just to find some motivation and energy to remove transmission. Not feeling any younger lying on a cold garage floor
The summer season is over here in Finland for this year but I would like to get it fixed before winter anyhow, so the car would be ready for next season


"The shaky gauge readings in R are probably due to the over-pressure relief valve (used after early '68) especially when modified by the B&M kit. It relieves pressure and then resets causing the needle to be unsteady"

Seems like a logical explanation. Thanks for your replies !!

Just a kwik and to Mr. Kunkel and Transman for all the knowledge they've shared and help they've provided over the years

the experts on everything torqueflight !

Indeed...I have to admit I did search for a mopar forum that was still "alive" and where Mr Kunkel was still replying to people So yes thank you Transman and Kunkel for all you've shared over the years !!

Had some time to start with the transmission removal this weekend. I noticed then that for some reason (broken clip/bracket? ) the return oil line/hose to the transmission was laying on the exhaust headers (at least 1 feet). Could this be the reason of the malfunctioning, slipping 3rd, that the transmission was overheated ?
If so, could fixing the oil rubber hose location,and change of oil and filter be enough, or is the damage already permanent on the front clutch ? I guess so

So a short update on this story...

Before disassembly I air checked the clutches, and maybe I could hear some air leakage from the front clutch compared to the rear. Could also be that I "wanted" to hear
The transmission is now disassembled, did not find any major things, other than a really burnt front clutch of course. The seals on the piston was looking good, but 25 years old and maybe a little stiff. So I still hope/guess that was the root cause.
Rear clutch was fine, could still see the stamp B&M on the clutch plates so they were as good as new. Both bands were also fine.

I have had 5 plates in the front clutch but now included in the masterkit that I bought was 4. So I have to look for a thicker snap ring to decrease the clearance a little bit before assembling.
The endplay of the input shaft was also in the spec but high end, so will also try to find next thickness for the washer behind the pump.

But one question / concern
The low reverse servo piston is quite loose in the bore. Have not had any problems with it before, and I have had the stiffer spring from the B&M shiftkit in there. I could get a 0.019" when measured with feeler gauge...so is this something to be worried about or is it supposed to be quite loose ?

i would think it should be somewhat tighter than that ?
just thinking in terms of fitment that i practiced when working as a machinist for 45 years.
mr. Kunkle would know for sure.
i did a fast scan through the Monroe book, but other than stating the obvious inspection of the bore and piston for gouges and cracks, plus making sure the ring[s] fit the groove[s] properly and spin freely, i couldn't find anything pertaining to the piston to bore clearance specs.
this was just a fast scan, so i may have missed something.
when i have more time [what's that ???? ] and i think about it [remember about it would be the correct term !] i'll have to investigate this further.

The rear servo piston is a loose fit in its bore, they're notorious for cocking in the bore and jamming.

I will use the old piston and hope for the best

one question regarding the incoming axle seal rings. I have had metal hook-up type but now in the masterkit it was non metal (teflon?) and no hookup. But I assume these are as good as..or ?

mine slips going into 3rd.im going to convert to a 4 speed this wintter

I would check the old seals removed from the reaction shaft support (large steel rings). Are they worn on the sides? Stepped? If so, their ring grooves are probably tapered. In this case the support should be replaced. Also look for ring wear on the mating surface of the drum.
Doug

As Doug mention plus -

Make sure all seals in front servo are in good condition.
Frt servo piston and retainer are not cracked especially the retainer where the guide rod runs through it.
Servo bore is smooth.
Place the reaction shaft seals (hooked together) into the frt drum bore. It should take some effort to do this, unless you use Teflon seals.
Make sure the frt drum large piston seal groove is in good condition. Make sure the inner seal bore of the piston is nice and smooth, if not polish it with micron paper. Don’t put a cross hatch in it.
Check the frt drum large bore for smoothness. Polish if necessary.
There is a long and short lip seal available for the inner drum seal.
My guess is heat aged rubber seals. The newer kits use Viton seals where the old were PA. PA ages quicker, Viton doesn’t.

Thanks for all the advices, I appreciate them a lot !!

The old seals on the reaction shaft looked ok, not any obvious there. The ring grooves also looked ok, but I could maybe feel some minor there so polished a little. And the new seals feels tight into the grooves.
The frt drum bore had some ring wear, so made me a little nervous at first...but when I tried the new seals into the drum bore, as per your advice, it felt good and tight. So I did not change the drum at this point.

I changed the frt drum piston seals some days ago and the bore looked fine.

I did receive a thicker snapring for the frt clutch, and also a thicker washer behind the pump, so yesterday I put the transmission back together. So I pray and hope it will last another 25 years now.
So the worst part is still to do...to get it back into the car I will try to find some time for that next week. I'm feeling too old laying on a cold dirty concrete floor

Just another update
So over last weekend I did get the transmission back into the car, filled up with oil...had the car idling, standing still, went through all the different gears with the shifter a couple of times back and forth...leaving it finally in neutral and checking the oil level. Filled up a half a quarter and then it was ok.
Checked for any oil leakage and everything seemed dry and fine.
Then put in reverse and backed the car out of the garage. Whou, that worked so at least I didn't mess that up Then slowly went for a test ride...1st gear fine....shifted smoothly to 2nd...but then the engine revs more and more...and I thought what is happening ? then finally it shifted to 3rd, very soft and almost slipping.
I backed of the throttle immediately, slowly stopping and starting feeling nervous. Tried again from standstill. Same thing, 1st gear fine, 2nd fine and then a late and soft 2-3 shift. I then drove for a couple of miles to get everything warmed up and the 3rd stayed in, did not slip even when accelerating quite hard.
Then stopped again, turned the car around. Felt the same once more...soft 2-3rd shift. Then I tried the WOT and kickdown, shifted fine down to 2nd....revd out to 5krpm and then it felt as the transmission missed the shift and flared. I was so disappointed...went slowly back to the garage, thinking I have to do this all over again.

I left the car outside the garage in neutral idling, thinking what now... ? But I decided to check the transmission oil level once more. It was low again, so I filled up almost 3/4 quarter. I just thought I would give it one more try, if the oil level could have done this. But I did not have much hope...
Went for the second test drive 1st gear fine, 2nd gear fine and believe it or not 3rd gear also fine and firm and at normal rpms. I stopped and tried again now with hard acceleration...and firm 1-2 and also firm and crisp 2-3 shift. I drove around for 30 minutes, accelerating, shifting and everything seemed ok now. What a relief !! It will shift smooth when driving slow and cruising around, and then crisp when giving more throttle and full acceleration. Fantastic....

But it is freezing cold here in Finland now, so I can not confirm how it will run on a hot summer day. That I'll have to wait 7 more months for. Hopefully I will remember to make a last reply here when that day comes
Thanks for all the advices and help !! It was nice to refresh my memory how the 727 worked once again.

AWESOME!!! and thanks for th update

glad you had success !