Lost reverse, need help finding it. 727

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Mopower71

Speed Demon
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My very low mileage 727 lost almost all reverse . tried to take it out of the garage on father's day. Started backing out of garage and everything seemed ok, had to pull back in to get the angle right to get past the tree. Put in reverse again and it seemed to be slipping, really had to rev it up to get it moving. Pulled forward again and it goes forward just fine. Tried reverse again and its getting worse. Pulled it in checked fluid and thats fine, nice color and no burnt smell. Let it sit a week or so and drained the fluid, pulled the pan .No clutch material in bottom of pan, just a little drag residue in the bottom of pan.
Checked reverse band adjustment and it was fine.
Where Do I go from here. Pop the reverse servo out?
Everything was fine about 2 months ago when i had it up and down the driveway a few times.
727. Had new clutches, and bands performance, don't remember brand they have been in quite a few years. But it only has a few passes down the strip and probably less than 100 miles on it. Also has a reverse manual cheetah valve body, 4000 stall converter , and a deep pan with filter extension.
Need help finding reverse.
 
Was the pump replaced when it was freshened up? May be the torque converter leaking down. I have a 06 Ram that sometimes won't move back in reverse until the pressure is pumped up. Also, had a 71 Charger that we had the trans rebuilt and the guy didn't replace the pump and it worked for all of 5 minutes before completely stop working.

Just a few thoughts. Good luck!
 
Don't remove the servo unless you see visible damage. If nothing is visibly damaged, no servo or low/reverse band damage (broken), then you need to put it back together, fill with fluid, and do pressure tests. If all circuits pressure test within spec, the front clutch pack is smoked.
 
Don't remove the servo unless you see visible damage. If nothing is visibly damaged, no servo or low/reverse band damage (broken), then you need to put it back together, fill with fluid, and do pressure tests. If all circuits pressure test within spec, the front clutch pack is smoked.

The problem with that is that for a person that has never seen or dealt with it before probably won't be able to tell if there is servo damage.
Some just crack around the lip edge and is hard to see until it's out.

No junk in the pan and no bad smell or color to the fluid, I would soooo be pulling that servo and inspecting it.
 
I'd take the valve body out and air check it. Next pull the servo and see if it's cracked. If not your taking the transmission out cause it's up in the front clutch pack.
 
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I understand that when using a RVMB, that the higher pressures put too much strain on the reverse servo. Mine broke, and I had a billet one installed.
 
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The problem with that is that for a person that has never seen or dealt with it before probably won't be able to tell if there is servo damage.
Some just crack around the lip edge and is hard to see until it's out.

No junk in the pan and no bad smell or color to the fluid, I would soooo be pulling that servo and inspecting it.

Yes, there is no junk in the pan, no burnt smell, and fluid looks normal.
I figure it might have something to do with the servo, but figured I would ask.
I will pull that out next, and check for cracks.

On another note, the car runs 11.83 @ 113. People have said the tranny is probably slipping , say the mph is low for the 6500 trap speed.
440, 4000 stall converter, 4:11 spool, 27.8" , tall tire.
 
On another note, the car runs 11.83 @ 113. People have said the tranny is probably slipping , say the mph is low for the 6500 trap speed.
440, 4000 stall converter, 4:11 spool, 27.8" , tall tire.

All I can really tell you on that is that if a trans slips for 15 seconds it's burned up.
Trans slippage is a misconception among most, in that there isn't nearly enough clutch material or a tough enough material currently to have a trans slip for even a few seconds without burning something.

They are not like a clutch for a 3 or 4 speed where you can slip the clutch multiple times and everything is still fine.
One and done describes an automatic when it slips.
Of course there are instances when a trans slips from fluid being low or a filter being loose, and if caught immediately it can sort of recover from that, but in a race scenario if your trans was slipping it would be a burned black fluid mess before you ever reached the 1/8 mile.
More likely it would be a converter with too much stall or an internal problem in the converter. (IF anything is slipping at all)
 
Thanks, leads me to believe, its the converter more than anything. Fluid is clean. Filter was tight.
Should I be able to push up the piece that the spring sits against by hand for the reverse servo?
The spring above it is weak enough that I can probably get the clip off without compressing it with a tool to squeeze it.
 
Thanks, leads me to believe, its the converter more than anything. Fluid is clean. Filter was tight.
Should I be able to push up the piece that the spring sits against by hand for the reverse servo?
The spring above it is weak enough that I can probably get the clip off without compressing it with a tool to squeeze it.
That spring isn't all that strong so I'd strong I'd expect you could push it up by hand. I'd air pressure test the servo itself before I disassembled it. If it air tests good with 35-50 psi of pressure that tells you it's fine. If you need a air pressure test chart here it is
 

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That spring isn't all that strong so I'd strong I'd expect you could push it up by hand. I'd air pressure test the servo itself before I disassembled it. If it air tests good with 35-50 psi of pressure that tells you it's fine. If you need a air pressure test chart here it is

It's kind of a PIA to get back in but I have taken them out by hand while in the car.

The only problem with air testing is most people don't know if what they are hearing when they pressurize something is normal or not.
The only way I can describe it to the OP is servo's leak almost no air when pressurized and clutchpacks do have some normal leak by due to the air having to go by sealing rings and such that do leak some air normally.
You or I would know right off, but someone who isn't familiar with it may not be able to tell what's normal.

Not to argue with ya Tracy, but in this case I feel a visual inspection of the servo piston and seal may be best if he can.
 
Trailbeast is right, a trans clutch or band that has actually slipped won’t last a Few seconds before it wants to weld itself to the contact surface. Had a front clutch that slipped and fused 2 clutches and 3 steels together. Vehicle would move foreword in neutral. A band will just smoke itself til it hits metal or just wont engage anymore. Smoke will pour from the dipstick tube if you can actually slip friction material. What most people feel as a “slip” is really just bad shift overlap, slow engagement, etc. Bands being too tight or loose. Or the wrong ratio levers. The overrunning clutch can slip and cause problems as the cams and springs wear out.
 
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That spring isn't all that strong so I'd strong I'd expect you could push it up by hand. I'd air pressure test the servo itself before I disassembled it. If it air tests good with 35-50 psi of pressure that tells you it's fine. If you need a air pressure test chart here it is
Thanks for the chart
 
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Is this what it should look like?
Reverse servo is the rear servo, front servo is kickdown servo?

15302248670394818921988452186184.jpg
 
The problem with that is that for a person that has never seen or dealt with it before probably won't be able to tell if there is servo damage.
Some just crack around the lip edge and is hard to see until it's out.

No junk in the pan and no bad smell or color to the fluid, I would soooo be pulling that servo and inspecting it.
And we have a winner. Thanks traibeast.
That servo got hammered .
Now I just have to get it past the arm. Been so long sinve I have had the transmission apart. What will fall out if anything when I back the adjuster all the way out.is there a way to get the arm far enough out of the way?

0628182041_HDR.jpg
 
And we have a winner. Thanks traibeast.
That servo got hammered .
Now I just have to get it past the arm. Been so long sinve I have had the transmission apart. What will fall out if anything when I back the adjuster all the way out.is there a way to get the arm far enough out of the way?

Nothing will fall apart if you back the adjuster all the way out.
If you cant get it out past that lever, the pivot pin will need to be removed.
You can only get the pivot pin out by pulling the tailshaft housing.

You don't have to have the whole trans apart like this, but it shows the pin and where it is.
The part laying right in front of his hands is the band anchor which also goes on the pin with the lever and needs to have the end of the band hooked on it.
 
Nothing will fall apart if you back the adjuster all the way out.
If you cant get it out past that lever, the pivot pin will need to be removed.
You can only get the pivot pin out by pulling the tailshaft housing.

You don't have to have the whole trans apart like this, but it shows the pin and where it is.
The part laying right in front of his hands is the band anchor which also goes on the pin with the lever and needs to have the end of the band hooked on it.

TrailBeast I Tried to P M you, but your inbox is full, to see if I can pick you brain and obvious knowledge on transmissions. If so please pm me when you have time. Thanks
 
Here it is, came right out when I figured out the right way to turn it.
Now to find a replacement. I see there are at least 4 differtent brands. Some reuse the spring, and some are just a solid billet aluminium piece. One is a wider steel piece that uses a seal and something else with it.

0629182140a.jpg
 
Never had that issue with at least 6 727’s. Interesting!
 
TrailBeast I Tried to P M you, but your inbox is full, to see if I can pick you brain and obvious knowledge on transmissions. If so please pm me when you have time. Thanks

Cleared it out.



Here it is, came right out when I figured out the right way to turn it.
Now to find a replacement. I see there are at least 4 differtent brands. Some reuse the spring, and some are just a solid billet aluminium piece. One is a wider steel piece that uses a seal and something else with it.

The billet ones are best, and will keep that from ever happening again.
Check A&A transmissions online.
These steel Super Servo's are nice also.
Dodge A727 A518 46RH 46RE Transmission Low Reverse Super Servo Billet K029 | eBay
 
I'm late with this answer but my internet went down june 30 and they just got it fixed last week and I've been super busy and trying to catch up.

Glad you found the problem. Hopefully you've got it fixed but if you don't and run into problems getting the band lever far enough back you don't have to remove the tailshaft, you can stick a screwdriver up there and compress the band and pop the little strut out that connects the band to the lever. It's just a little piece of steel about and inch square. When you remove it the lever will pivot all the way back and you can service the servo easily. Reverse things to re-install the strut
 
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