Howdy!

I posted a thread about my recent trans carnage- I shattered a stock slip yoke and took out my tailshaft and trans case. I called A&A trans (board sponsors) and ordered solid 1350 universals and billet steel trans and pinion yokes.

Now I’m looking at options for my next 727 build. The numbers on my current broken trans say it’s out of a ‘77 2wd pickup truck. I would ideally like to find a similar trans so that I can pick the healthiest parts from both cores to use. I’m looking stuff up in my books and in the tech archives and I think I have a good idea of what to look for but I’m posting now to get more experienced opinions.

If my info is correct my valvebody will work in any post ‘65 727. My oil pump and front drum will only work in a late trans- 76+? And my planets and forward clutch will not interchange at a certain year down right- output spline change?

Am I correct that all my guts will work in any post 65 case + tail? I want to stay with direct interchange for all or most parts if possible though. I don’t really care if I have kickdown or neutral safety switch- my ‘54 has NSS in the slap shifter and didn’t come with reverse lights.

I want to use my current B&M neutral balance non lockup converter- it was working great, along with my clutch drums, planets, shafts, clutches & steels. I might play with a higher numerical kickdown lever but I dunno.

Any input on what years I should be looking for? I can get a good ‘67 core but I don’t know how much of my guts could swap and if the planetary gears and clutch drums are different (oil passages, oil pump, splines?) then I’d have less parts to pick from and no spares if the new core turns out to be beat up.

Thanks Moparts!

Radar

1971 is when there were a number of changes done, both to the 727 and the 904 in the range of PK35XXXXX and up. Cases, fluid passages, etc. should be the same except for some servo sizes on the small transmission, except for the mid 60s. style units. Internal parts have been changed. I would think anything in the mid 70s would be fine. I'm sure others can be more specific and will chime in.

If that thing was broken that bad, I would check shafts for being bent and closely inspect everything else.

In the year range you're proposing there were lots of changes that can get you in trouble when swapping parts. For instance, besides the changes to the case and VB in '71, there was a change in the output shaft spline in '76 that affects front planetary interchange and there was a change in the lube circuit in '74 that affects the valve body and input shaft interchange.

Best to ask the exact year you're planning to interchange,.

Ok. Will my tf2 modded 1977 valve body go in a ‘72? How bout a ‘68? Again- I don’t use the trans nss or reverse light.

Why not just repair the on that broke? Take it apart and see what broke. You'd be surprised how much power you can put through one. I know, all 727's blow up and kill people. A good drum, front planet and valve body will hold a fair amount of power. We have 2 push button units that hold north of 800hp with mainly stock parts. Mine is nearing 600 passes with no real failures.
Doug

That’s pretty much what I need to do- I need a case, tail, output shaft & matching parts- possibly a governor, park stuff, etc. Buying those ‘a la carte’ will quickly exceed the cost of a whole used trans. And if I find a similar year I can even see if any of its parts are healthier than mine.

Either way I need to build a whole trans and I wouldn’t use anything from the sprag back in mine. So all I have here for sure is a non lockup converter, ‘77 clutches, drums, bands, servos, pump, struts, and my modded valve body with deep pan & filter. I want to use those parts to ‘fix’ my trans but if I can’t find a compatible core it is actually cheaper to just buy a complete rebuild kit for whatever I can get a hold of- unless I end up needing planetary gears or some expensive part that’s worn out. That’s why a trans that my parts swap into makes a new core less of a gamble that way as long as the tailshaft contents are good I have my pick of two sets of parts.

I’m just studying my books and looking at date interchanges on parts for sale and asking questions here to try and educate myself on the interchangeability of all the 727 guts cases and valve bodies.

As John pointed out, using a 1976-1978 for interchange is the best way to go, IMO.
Some earlier parts work, but if you are buying a transmission for interchange, '76-'78 non-lockup version.

On Sunday I took my 7yr old on a road trip mission to get a free (I couldn’t show up empty handed- brought a case of adult sodas 😉) trans case from near picatinny arsenal in NJ from a generous moparts member. He said did I want a pile of internal parts to go with it so I said sure of course! Turns out the case was exactly what I need- 1977 big block 4wd dodge truck #s on it, but the assembeled tailshaft is post 66 pre-71. I think the rest of a matching trans is pretty much all there- and it’s got two 4 gear planetarys & a high groove 4 clutch front drum. The tailshaft looks clean except the output shaft that sticks out of the front is surface rusty. It’s missing servos, one band, both band linkages, and the shifting side of the valve body. I think I could build it up pretty easily after confirming the gears and splines are all from the same trans. He threw in the Munroe book- wow! I had the Tom Hand book already and the second book really cleared up some stuff and it’s definitely worth having & using both. yella71 is a great dude!

My local buddy that has a pile of cars in his backyard said he might have one I can have and I asked him for a phone pic of the PK#. He said he did find it in his stash but it was dark and dirty he couldn’t het the #s. I said for zero dollars no need to make him do any work I would come get it and I can wash it.


PK4028412
1977 Chrysler passenger car
400 std. 2 barrel motor non HP
Casting date Weds Dec. 1st 1976

Perfect swap for my internals out of the busted cases- '76-77 are all the same spline counts & planetary gear angles etc. '78 was 1st year lockup converter. Mine was also a '77 so I can clean this one up, record the endplay, disassemble both and have my pick of the best parts and spares. I’m gonna keep the extra 77 case and I’m happy to keep the 80% of a HD early set of guts but if somebody needs em PM me!

Anyway I’ll get around to cleaning my garage into an operating room this week and try to find time to pull the broken trans and start taking these suckers down.

Thanks for the help fellas and I’ll post autopsy pics in my carnage thread when I get em!

Couldn’t stand the suspense after I noticed the dipstick tube on my new core was open and it had been stored outside. Could have been flooded & rusty in which case it’s only a set of donor cases. I pulled the pan and it was pretty gunky but no water, a little clean red fluid hanging out (must have been drained when pulled from a car). Somebody loved it and wasn’t a great wrench- it had a large brass filter installed, all the VB bolts were a little too tight, and one was rounded off some.

Under the valvebody it looks like a nice clean core. Hopefully the output shaft isn’t rusty I won’t be cracking it all the way open until my shop is clean enough to lay it all out on butcher paper.

I like using the older front servos, two springs and the smaller pin. Some late 70's truck 727 had them too.
The newer servos are "oil cushioned" on the shift. Not the best for racing.

Thanks Jim

I am not really racing this thing unless you count trying to beat mustangs and camaros from 0-35 at a light. I am trying to be a grownup with this build and basically made healthy modern diesel power but in a 3200lb pickup on premium pump gas. I just wanna cruise around and occasionally lay some stripes and stuff myself and passenger into the seatback.

I had already ordered billet steel 1350 slip and pinion yokes. Today I ordered some more stuff from A&A - a 4.2 lever, reinforced band strut, and a billet low/reverse servo piston kit, along with an overhaul kit so I have plenty of seals, bushings, red frictions & kolene steels in case the 100 miles I had on the trans were harder than I thought.

I also got an iron front high groove drum. It’s not that I don’t think my right foot is worth $700- it’s just that I launch at 3000, shift at 4500, and my spark rev limiter is set at 5500.

I think I won’t do any more holeshots in Drive though- 2nd gear only from now on.

I was looking hard at the billet steel drums and ultimate sprags but I just can’t justify the cost for a maybe 12 second street machine.

Plus if I ever get bored with my HP and get trickflow 270s, roller cam, and big headers I will have enough trans parts on hand to get a good headstart on building safe high rpm 727 for the strip.

Am I a fool? I already will have around a G in this rebuild once I get a new driveshaft made up for the 1350 u joints.

The controlled-load front servo is easy enough to defeat, Transgo kits supply a spacer to eliminate its function or you can drill and tap its feed hole (red circle in pic below) and block the hole with a set screw.

These are the dimensions I used in the past. In case somebody whats to make that shim.
I had plenty of the early servos, including from '77-'78 truck transmissions; so I never ran the shimmed later servo.

I hadn’t looked at the controlled load servo before as a possible upgrade point for firmer shifts. I couldn’t find much on forum searches either. I have been studying the Munroe and Hand books like crazy and the Munroe book has the mod in it but if there’s a good paragraph on function cause & effect I didn’t find it. All I did was inspect for cracks or scratches and reassemble with new seals in my last 727 build.

Looking at the parts and y’all’s mods what I’m seeing is the later servo is made more like a hydraulic lifter? So I guess pressure would bleed in and out of that little hole and create a cushion of oil for the apply rod (wrong name? Is it piston, retainer, rod?) to ride on?

So shimming it would eliminate travel and defeating the hole would eliminate oil pressure below the rod base? Either way the lower piston would have the apply rod in direct contact and could probably release faster.

Couple questions- first are there any changes that would need to ‘agree’ with this mod? I’m guessing the rest of the timing could only be improved with a faster 2nd gear release as another gear applies?

Second- how would pressure even get under the rod in any meaningful way to create an oil cushion in the first place? Doesn’t the lower piston with all its surface area apply quickly enough to take all of the KD lever’s travel before pressure could flood under the rod?

I’m getting closer to actually wrapping my brain around all these functions- the more I learn it all seems simpler.

Thanks

Radar

You have to remember that the servo piston is restrained from moving by a large coil spring that keeps it seated in the bore when no pressure is applied. When pressure is applied to the servo, the spring resists piston movement until a certain pressure is attained to overcome the spring but the same pressure is also entering the small hole in the piston and its weaker spring allows the plunger in the piston to move at a faster rate than the piston itself, thus the pressure under the plunger gives a cushioning affect on application and a delay on release. Plugging the hole or blocking the plunger defeats the cushioning and makes the servo, in effect, the same as the early servo.

The thing I dislike about the controlled-load servo, other than the cushioning effect, is that the plunger remains extended from the piston even after the 2-3 upshift; this closes up some of the free play that is adjusted in and mandates looser band adjustments. As you can see in the pic below of the piston in 3rd gear, the plunger is still extended even though the piston is firmly seated in its bore.

Contrary to many people’s belief this servo design is to reduce 3-2 kickdown, the 1-2 is a secondary benefit.

Thanks fellas! Great info and pics.

Took down the new '77 core. Guts look good, endplay was good.

Sprag race was a little loose and the rear cooler fitting is sheared flush. Gonna clean and inspect the other '77 case I got in NJ tomorrow hopefully I can avoid buying a bolt in sprag or messing with easy-outs.

I couldn’t wait- I took the other ‘77 case down, simple green’d, scrubbed, power washed, dried with compressed air, and hosed the sprag race with wd40.

It looks much better than the first one off the complete trans core I disassembled this morning- tight sprag race, all tapped holes good, all sealing surfaces smooth.

It’s interesting that the casting dates are only 9 months apart but the good one has more ribs/reinforcement in the starter area. Had to do a double take and measure the top bolt holes to be sure they’re both big blocks!

Edit: left is dodge truck rt is chrysler car that could explain it? Truck bell beefier?

I never noticed that feature near the starter mount.
The 1973 case I have handy has the rib.

I went with the drill/tap on the front servo. 6/32 took all of five minutes to do. I brakleened it and glued it in with a drop of loctite hydraulic sealer and some loctite primer spray. The little allen grub screw sits just proud of the outer surface and not too deep inside.

I’m still waiting on my trans internals from A&A but my yokes are here. What do y’all think-this old driveshaft and yoke should be fine to just run right? Hahah