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727 Issues, No forward gears but reverse works. Rebuilt

11K views 12 replies 4 participants last post by  chau8238 
#1 ·
Alright, so I just went through and replaced the clutches, seals, and some of the hardware inside of my 727, it's a 77 big block transmission in my 85 Ramcharger.  Although, after looking at the valve body (stamped 67) this might be an older transmission since it was rebuilt in 99.  Anyways, it worked before hand, but slipped heavily in first and after tear down, the rear clutches were shot, pretty much metal on metal.  Anyways, get it all back together and now only reverse works, put it in Drive, 2 or 1 and no movement.  I actually did get it to move about 3 inches once, but that's it.  Reverse works all day though.  I've swapped valve bodies, adjusted the bands, did an air check and both servos lock up, although the kick down servo seems to leak air quite a bit more than the reverse, so maybe that's the issue? 

Anyways, any help would be appreciated.  I'm tired and I've been searching online, but the only thing I could think of now is that maybe a wrong part was used since some parts were sourced from the 85 small block transmission that was original to the RC. 

Thanks for any help/suggestions.
 
#2 ·
i believe i know what your problem is. if you used parts from the 85 tranny in your older 70s tranny. you have to make sure you use the same pump and input shaft and rear drum assembly. they have changed the way fluid routes through the pump to the input shaft and into the rear clutch assembly. if you used the 80s pump and 70s input and rear drum (or vise versa). you will have no go forward. but reverse just fine. you must keep these parts matched. sad to tell you the tranny is gonna have to come back out if those parts were mixed.
 
#3 ·
That's what I'm thinking the issue is.  I've been searching online and finding vague information on the issue. 

I used the original pump, but some of the internals were used from newer transmission. 
 
G
#4 ·
          I believe 78 up the front pump and input are the same. 77 down are different. Two sealing rings on the 77 input shaft and three on the 78 up. Pump and input have to be matched. If mismatched there will be major psi loss.
 
#5 ·
I can't remember what parts I used, I know I used the rear drum from the 85, but I can't remember if I used newer or older one for the input.  I have all of the parts, but they are currently in Indiana and I'm in Texas. I'll be home for Christmas, so I guess I'll get the right parts then.
 
#7 ·
I replaced the seals, no press needed, just large C-clamps.

And after thinking everything through, I used the wrong input shaft, I believe that's the only part that's different. I still have the original one, so I'll swap it out sometime after Christmas unless I get it mailed down here.

Quick Question, is the pump and input shaft the only thing that's different? I just want to make sure I didn't swap anything else that might cause issues.

What I used.

New Seals from a rebuild kit, also had new clutches, metal spacers (between clutches).
Used Original Pump, piston retainer assembly, clutch assembly, and valve body.

Things I used from the newer transmission (what I remember off hand)
input shaft and piston retainer and low and reverse drum was used along with the planetary gear assemblies. I believe everything else was re-used or swapped out with the rebuild kit. I can't remember if I used the piston retainer for sure or not, but I'm thinking the newer style was used.

I just want to clarify, that the low and reverse drum was used because the original one was only wearing on the outer portion of where the band sits, so it wasn't sitting flat on it. Also, it had at least 5 "balancing" holes in it whereas the 85's had no holes to balance. I'm not sure if that part is the same overall or not though.

The 77's transmission


The 85.


I've been using this to guide me as far as the differences. I used a Chilton's Automotive Service manual to guide me in the rebuild. It has full breakdowns, but of course being from the 70's, never mentions that the newer ones were different, so that's a mistake on my part. But at least an easy one to fix.

http://www.ihpartsamerica.com/forums/transmission-tech/2516-t-407-tf727-variations-parts-differences.html
 
#8 ·
you should be fine with the rest of the internals. valve bodies are slightly different but still route fluid to the same ports. instead of changing the input shaft you could just install the 80s pump for a quick fix and not have to pull the drums back out.
 
#9 ·
Need to double check the shaft/spline engagement on the planetaries if you mixed any shafts. Spline count's the same, but the shape of the teeth varies between years. Can lead to stripped splines. Can't remember the year breaks on the design changes.
 
#10 ·
Alright, I'll probably just swap back in the old parts, and I might be buying a spare 70's transmission for parts if needed.
 
#11 ·
Got some good news, picked up a 72 small block trans for the parts I need. It appears to be in good shape and the clutches look new even. Not that I'm going to use them since I have new clutches already in mine, but good to know at least. I think it's from a 72 Charger. So before I swap parts and install it, this will work right?

The 72 small block for parts.



The clutches look new.


The shaft on the left is what I needed.


Looks like it had some contamination while sitting, but all of the internals look good to me. Everything I need at least.



The port that I needed, the newer style moved it further back so it's not interchangeable.


Looks pretty good.






This is the number on my transmission.



Also, if anyone knows what year transmission my case is, I'd appreciate it. It's from a 77 W200, but the valve body was stamped 67 so I have a feeling the case may not be original either.
 
#13 ·
Alright, so I swapped out the input shafts and now it works like it should!  I appreciate everyone's help, and I'm glad the 727 is a simple transmission.  Hopefully someone won't make my mistake, and if they do, will find this thread easily.  I'm just glad to have a working RC again.
 
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