Edit: 727 is out and apart- here’s what I found

Howdy fellas

I’m getting a little more seat time in my hotrod and it’s becoming obvious that something isn’t right in my transmission. If you didn’t see my earlier thread I couldn’t get any gear at first because I had installed the pickup/ filter extension for the deep pan 180° out and wasn’t building line pressure.

I’m a little bummed I have more work to do but doing it is the best way to learn right? I’m hoping I can describe my symptoms and say what I’m thinking based on my very limited understanding of the 727, and get confirmation or correction & guidance from all you 727 experts.

-atf level good
-shifter synchronized/indexed properly
-cable style theottle pressure lever adjusted for WOT and fitted with a return spring
-tf2 kit installed
-2400 holeshot converter
-1 manual works great
-2 manual same
-D shifts quickly through 1-2 at low throttle, hangs on to 1 longer with more gas, never seems to shift into 3rd/direct
-R sometimes shifts and works good, sometimes acts like neutral, sometimes bang bang bang jerks you backward hard and shudders

I’m not sure if I ever had 3rd or not but it just never seems to go into cruising gear. I have a 512 motor and 3.21 sure grip so second gear will do 60mph pretty easy. Around my neighborhood and some bigger streets it does a really nice footbrake burnout (instant smoke) and breaks loose the tires at 30mph if I mash it a little. So I guess it must have some pressure and the rear clutches working?

So since the front clutch seems to be the one thing that reverse and 3rd have in common, and reverse has a mich higher line pressure, I’m thinking the piston is not sealing? Or something is amiss there.

Should I go ahead and buy some pressure gauges? What is an affordable option and do I have ro cobble together a 727 tool or two with hoses long enough to see from safely not under the car? 100 & 300 psi guages right? Links or advice mich appreciated.

Should I assume that it is the front clutch that is causing this or is it possible that the problem is in my valve body- possibly a swapped or backward shaft or a check ball causing this? Band adjustment?

Should I go straight to an air check on the front clutch? What am I looking for and am I on the right track trying to fix it?

If I keep finding problems I’m really gonna be an expert soon haha

Thanks for y’alls time and patience
Radar

Air check the front clutch. If I were a betting man I'd say you tore the outer piston seal on installation. Did you have trouble getting the piston to drop into the drum?
Doug

In these cases where a shift kit has been installed and not already tested, I always recommend installing a known good unmolested valve body. That is about the easiest and cheapest test before you pull the tranny. Of course, valve bodies used to be everywhere. That is not true anymore.

And you can air check the front clutch at the same time.

If it stays in 2nd, it's a possible control/kickdown/governor/VB problem, i.e. the 2nd gear servo is staying on. If it goes into a false neutral and freewheels instead of going into high, then it's the front clutch not applying. But, since reverse is also not right, you are correct that the high clutch is the common element. Multiple things going on. A pressure check of different functions would help. Or as suggested, swapping in a known good VB would confirm or rule out all of the issues being valve body related. Band adjustments also need to be verified.

When in doubt if it's in 3rd gear, throttle back to idle and shift to 2nd...if it noses over it was in 3rd.

I am going to remove the VB and start with a front clutch air check at 150 and 40 psi to simulate R and 3rd under the assumption that if 1&2 hold so well I must have some line pressure in D and more in R. If it’s the piston seal I’m thinking I might hear engagement at high psi but disengagement will be almost instant instead of a quick sigh and at low pressure I’ll get no thud just air rushing.

If it seems to hold at both psi and not leak more than it should then I will dig in to the valve body and look for a backward piston or missing check ball. I stayed up late studying my trans books- I think I sorta have a handle on the trans circuit operations. I need to study up on valve body operation. I think the selector& throttle pressure are working and the governor vs line pressure is properly controlling the upshifts in D, at least until it needs to go to 3rd.

I never had a high stall converter before or built an auto before so I am not sure if it is sort of selecting D then slipping or what, but a lack of front clutch apply would seem to be a good candidate for my troubles. I remember doing the whole electrical tape and 15 mins in the freezer thing on the piston to try and get the seal to face down on the way in and I lubed it but did I air check it I dunno. I don’t remember it being particularly easy to install but I didn’t think I forced it…

In any case this is a new build with a handmade floor, firewall, console, etc so I was tempted to finish sealing and painting the bottom on a buddys lift but now I’m motivated to do it right- call this a successful mock up, take the body off to nicely detail and protect the underside, and have access from above to easily R&R the trans.

Thanks fellas for helping keep me moving forward in the right direction! I’ve been building this truck since May and despite some setbacks it’s really starting to come together now. The 512 is strong and the breakin oil and filter looked good, it steers, stops, and goes like a bat outta hell. Always more work to do.

I gotta give you credit for doing it yourself! I've heard before that 727's are fairly simple, but obviously thats all relative. I personally hate pulling transmissions on my back, so for that reason alone, I would have it built for me to (hopefully) avoid any problems . Sounds like you're getting a handle on it, and you're learning a lot as you go. Hope you get it figured out soon.

Gettin closer! I was bummed about pulling the trans out the bottom but I needed to finish the bottom and firewall of the cab anyway so I pulled the body off and the trans is right there. My new 727 seals & gaskets just came in the mail today too.

Doing more research on the front clutch piston made me remember what a pain in the butt it was and how I knew that it felt iffy going in but the only way to check it is pulling it back out and starting over trying to get it started.

Last time assembling the piston I wrapped in teflon tape then electrical tape to hold it facing down and put it in the freezer for 20 mins to try and keep it tucked tightly down. The teflon tape was to make the electrical tape come off clean. Then I smeared it with sticky blue transmission assembly grease and tried to push and shimmy it home.

Anticipating a re-do of that job I read back up online and in my books. I read about using sonnax slippery stick to glue the seal tight and facing down but nobody sells it around me. I did find door-ease for sale on amazon which was mentioned in another book so I got a stick of it.

Does anybody have any wisdom about doing this job better prepared this time? It’s a late 70’s 727 if that makes a difference-takes the thin seal I think? Have you had luck with the super sticky lube technique? Is door ease even a good idea to try?

Thanks!

Ok I got her out and apart.

The air checks were all good except the front clutch which just blew air- no clutch apply sound.

I found a couple parts of a sealing ring in the pan- turns out they were off the snout behind the pump. My front clutch piston outer seal actually looked fine. It is flipped down, and not ripped or folded and needed a little pressure to go back home which I did twice inspecting between.

The kolene steels and red fibers saw some heat. The fibers are a little black around the edges and the frontmost steel (not the thick pressure plate) is noticably warped. I think I had some spares left over from the rebuild.

Could that steel sealing ring on the back of the pump be my culprit? The front clutch gets pressure from the reaction shaft right?

Thanks for the help fellas

Radar

Here’s the half smoked clutch pack and the replacement parts I have on hand.

Those two rings are for the front clutch drum - looks like you found your problem.
Check the mating bore in the front clutch for damage.
The reaction shaft support looks a little worn below the seal, I would polish that up with 400 paper.
Make sure the new metal sealing ring turns easily within that groove - I would carefully take a fine file and make sure no burrs or edges exist in the groove and follow that with more paper polishing.

Make sure you have the ends locked after installation of the seal in the support.

Not sure what reference material you are using but the built front and rear clutches when placed on the pump can be pressure tested on the bench by using a rubber tipped blow gun and approx. 30 psi.

Just hit each round hole (not the pump attaching holes) around the pump - one is for the front, rear clutch, the others are converter in and out so ignore those.

Using high presssure hides issues liked nipped rubber seals and damaged seal rings.

Absolutely found the problem, yes. The rings seal the drum feed. The thing is, there should be no way that any portion of the ring was found in the pan, unless the drum is now all ground to heck. The ring parts would need to be pretty small to fit between the support and drum. Could this have happened on installation?

By the way, you are pointing to the the fluid communication slot.

If you had the bottom seal ring there then you likely broke the seal on installation.

The seal goes in the groove just below your screwdriver tip.

I'd check the rings grooves for being square. Set a new ring in the groove and hold it up to a light. The grooves should not be tapered. They should fit square to the ring. If they're tapered the reaction support is scrap. Also check the surface inside where the smaller steel rings ride. It should be smooth with no grooves where the rings seal.
Doug

Is your clutch pack laid out the exact same way you disassembled it? If so it is wrong. Start with a steel on the bottom and end with a friction disc against the pressure plate.

Yes you found your problem. If you did not do it cut off some 5/16 threaded rod and screw two short lengths in the case to help you align the pump as you install. Buy some regular trans assembly lube, very thick, coat the rings after you install, it helps keep them from hanging and breaking. Lot of guy now use the teflon type rings, they wear the drum less and seal better at high RPM's Make sure the grooves the rings go into on the pump are not damaged, 727's are prone to wear those grooves, and make sure the bushing in the drum is good. If the bushing is loose the drum will wobble at high rpm's and take out the rings.



https://www.ebay.com/itm/DR-TRANNY-...SSION-ASSEMBLY-LUBE-M465TG-/192450963604

http://coperacingtranscom.ipage.com/?product=727-teflon-sealing-ring-kit

Thanks fellas!

The clutch pack did start with a steel- I accidently left it on the piston when I took the pack back out for the photo. And for sure I was pointing at the wrong groove in the pic! Long night...

Here’s some better pics of what’s going on here. The bore of the clutch shell actually looks really good to my untrained eye. You can see where the steels ride/seal but it doesn’t catch a fingernail and isn’t too wide so the endplay is probably ok too. This is the blue sticky assembly lube I have been using for the transmission. And the last two pics are of the damage to the sealing ring groove that had to have happened during installation. The pan had one little arc of sealing ring and a few crumbs. Most of the broken ring was still in the groove. If any had escaped during operation it would have chewed the crap out of the reaction shaft and drum inner bore- glad to not see $$ that. I think I can get away with touching up that ring groove so no burrs interfere with the ring floating freely.

I’m planning to replace the two warped cupped steels. The others are still dead flat with no bad burn marks. Also I’m replacing two fibers mostly because that’s how many spares I have. The fibers are a little black around the edges but not worn thin into the fiber material. Should I scuff the used ones with some scotchbrite? They don’t look real polished/glazed. When I first assembled this clutch pack it had 4 fibers and .045 clearance to the snap ring- when I pulled it the clearance was gone due to overheated cupped steels- one slightly and one noticably cupped/warped. I know I am on the tight side of acceptable clearance- I will re-check and verify it after I build it back up but I wonder if taking my pressure plate to the machine shop to have .020” skimmed off would be a great idea or a waste of time and money.

What thickness snap ring are you using? There are multiple thickness available. I believe .104" is the thickest. Drum ring surface looks OK. It the ring surface that the input shaft rings ride on inside the reaction shaft support. As I said check for ring groove tape with the ring in the groove. If its tapered it'll kill the ring in short order.
Doug

It’s a wave washer and it’s fifty thou thick. I have four steels & fibers in there and with some oil on everything there is basically no free play. My book says measure the clearance under the high section of the wave- I can probably fit a few more thou but .045” feeler guage slides in with no force. The fibers can move fairly freely but I think I want more clearance for the front clutch than the forward/rear right? A little room for the un-applied pack to spin freely but not so much that the seals could pop out? My book says with the wave washer I want .082”-.151”. Would milling .045” or .050” off the pressure plate be the easiest fix here so I don’t burn up my fibers when not in 3rd or R?

Thanks for the tip on ring groove squareness I’ll check that tonite!

The new rings fit very nicely in the reaction shaft on the back of the pump.

I did some measuring and it looks like if I sistered a steel under the pressure plate to make it .060 thicker then I could run 3 of the raybestos .065” stage-1 red clutches with .110 gap. I’m not doing that (!!) but if I had to drive it to work in the morning I’m thinking it’d work just fine- and might be a good way to be able to air check the piston before I get the clearance right to run the 4th fiber? With hopefully 500+ ft/lbs I’m going to get that 4th fiber in there! A machinist buddy said he could scrape 50 thou off the pressure plate nice and flat for me by tuesday. It’s up around .275” thick now. Maybe I should ask if he can machine a ledge around the edge and leave more meat in the center for heat dissipation and strength? Or am I overthinking it?

Can’t thank you all enough for the help with this 727. Next one I build will be easier!

Turbo Action (and probably others) sold plates machined just like that.

If your buddy does it make sure he leaves a nice radius otherwise it will break.

If your rear clutch is apart look at that pressure plate - some guys install that one upside down in the front clutch to achieve the same thing. It’s tricky sometimes to get the snap ring in and out but it works.

You can run the solid style snap ring like the one in the rear clutch. Then the ring will float upward in the groove.
Doug

Pressure plate lathed for more clearance.

john, does the chatter marks on the side of the lathed pressure plate affect anything ? i would do a better finish if i were doing that job just because.

In the alto power pack setup you can buy the pressure plate is .177 or something- dunno if its heat treated or chromoly or tool steel vs the stocker but to make it easy on the machinist doing me a favor I think mine will still be strong enough shaved flat at over .2”? The stocker is just under .280. That avoids measuring snap ring install clearance and chancing a stress riser in the corner from tool marks or whatever.

I have been doing and re-doing my math- with .045 clearance currently I can shave .037 to just barely get in spec at .082” I’m thinking a little extra room for the clutch to slip unapplied isn’t a bad thing since max spec for 4 plates is .151” My guy is coming to pick up the part and my instructions today. I’m planning to tell him I want .070 trimmed off which would give me just under spec until touching the wave snap ring and .115 total gap to flatten the ring. My tom hand book says to measure at the widest gap under the wave so that’d be at .115” which still leaves room to keep the piston seal in its bore as my fibers wear.

Sound like a good plan?

Also while the trans is out I have the slower lever in there- one line on it makes it a 2.9. I have a tf2 kit installed and kevlar bands. Obviously I haven’t yet experienced a 2-3 shift, the 1-2 was noticable but not harsh and didn’t slip. Should I be looking at a higher ratio servo lever and thicker band strut? Is tig welding a reinforcement on the strut worth doing? Again this is a healthy but mild 512 stroker but not a race car and on street tires.

Thanks
Rdr

.012"-.015" per friction is what most of us shoot for. So with 4 friction it should be .048"-.060" clearance. You easily tig weld reinforcement to the band strut .Make sure the ends of the reinforcement don't interfere with the band or band anchor.The ratio levers multiple servo force times ratio. The 3.8 or 4.2 seem to work well. The higher the ratio the longer the servo travels to engage the band.
Doug

My machinist said he took off .050 on the lathe, .009 on the surface grinder, then flipped it and took .002 of curve off the back to true the faces. So the plate lost .061”

Add that to my existing .045 clearance for the front clutches to freewheel and I will have .106” which is right where I want to be inside a specified clearance of between .082” and .151” for four friction plates. Hopefully right where I want to be anyway. I figured I’d shoot for a 30% over minimum clearance to be safe but not sloppy.

The plate was .280” so it will still be .219” and plenty strong for its purpose. Again, hopefully- I have no idea what I’m doing but I’m catching up fast.

I should have her back together late tonight and I’ll do an air check before re-installing the valve body. I will make sure to butter up and center the sealing rings on the reaction shaft with sticky grease so they stay centered and won’t hang catch and break when I bolt up the pump. I’ll also make sure I use pilot studs to keep the pump centered as it goes in.

Got the PP back- looks great and comes in 1/3 of the way from min to max spec at .106” clearance

[/quote]

.012"-.015" per friction is what most of us shoot for. So with 4 friction it should be .048"-.060" clearance. You easily tig weld reinforcement to the band strut .Make sure the ends of the reinforcement don't interfere with the band or band anchor.The ratio levers multiple servo force times ratio. The 3.8 or 4.2 seem to work well. The higher the ratio the longer the servo travels to engage the band.
Doug [/quote]

Dang I feel like I read this before which is why I thought I could get away with it at .045 when I first built it. Then this week going back through my Tom Hand book he lists the spec for 4 fibers at .082-.151 which is a lot more!

The last thing I want to do is pull this trans again real soon because my front clutches are burning up because I spend a lot of time in 2nd gear hotrodding and they are heating up instead of slipping. All the reading I’ve done talked about how the forward clutch has a small unapplied gap because it’s almost always applied where the front clutch needs some room to slip because it actually does a lot of on and off.

This is all book learning though- I come here for real world experience.

So by my book I’m at the bottom 1/3rd of spec and by your suggestion I’m at double the spec. Not sure if the wave snap ring figures into this? I’m guessing if I went straight snap ring it would apply harder with no cushion which would be harsher but easier on clutches wear wise?

It’s too late to un-shave my pressure plate but I could swap the .050 wave washer for a thicker flat one if it is a big deal?

The old saying - “too many chefs.....”.

Is this lou????

It will function at the larger clearance. The tighter number is what has been recomended for blue printed builds. This why I suggested simple snap ring change in an earlier post. Steels are also available in thin .070" and thick .085". to tailor clearance.
Doug

Thanks Doug.

Well she’s all back together and the air check sounds great on the front clutch now. (Forward clutch and both bands still good too!)

Another item of good news- I was a little terrified to pull the stock 1989 dakota trans crossmember in my chassis. I was thinking after shortening the frame 20” and boxing it all in there is no way it wouldn’t spring when I took the xmember off and it wouldn’t line back up to re-install. That plus needing to finish and paint the bottom of the handmade floor & firewall made me pull the body so the trans would come out the top. I pulled it today and the frame didn’t move at all when the bolts loosened and they didn’t even put up a fight! So any more transmission shenenigans can happen from underneath without pulling the cab again. I have fought trans crossmembers tooth and nail (& torch!!) before so this one will go back on with some anti seize!

Anyway, thanks all for the support and insight. I’ll report back after I crank her back up and hopefully get a cruising gear and a reliable smooth reverse gear.

Radar

Congrats on sticking it out.

Hopefully no more issues.

glad you are back together. hoping for the best for ya.

What kind of line pressure are you running. I use the machined down retainer plate like you have in your picture and never broken one. I build a ton of 47/48 RE Cummins transmissions with up to 220 psi and the plates hold up fine. Stock inputs, nope. I always check pressure once they are back in the vehicle, get some good gauges and go through the pressure tests before you drive and you will prove everything is correct.

Well I don’t have gauges and I am a total noob but what I can say is if I remember right the pressure setting is the screw that moves the little plate on the side of the throttle body? I put it a short and curly from touching, not quite flush. I believe I decided that was ok when I installed the tf2 kit. Most of the choices that kit gave I would go aggressive but short of brutal full race setup.

It must be a decent amount of pressure because reverse was trying to work and sometimes worked ok even with 1/4 of a sealing ring missing on the reaction shaft. That was with an initial setting of .045” clearance below the wave ring but after a while the clutches were burning up and one of the steels was warping in a cupped way that took up more slack...

I was just psyched that my front clutch air check now sounds awesome. I still have the wimpy lever running the kevlar front band set at 1.75 turns out from torqued. It’s all just guesses, I have worked on a million harley evo and shovelhead clutches which are similar to the forward and front clutch setups- bellville and coil springs respectively but mechanical releases instead of hydraulic applies.

The trans is all back together but still on the bench. I have time to make changes if they are important.

Line pressure in Reverse increases by a factor of about three so the increased pressure helps weak parts that would fail at the lower pressure in forward gears.

If by "wimpy lever" you mean a low ratio like 2.9, setting it at 1.75 turns out is a bad idea...the lower the ratio the more turns out. For that lever go at least 2 turns or 2.25.