727 build fail

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MoparMike1974

MoparMike1974

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Rebuilt my 727 and now it seems to be binding in two gears occasionally. Mostly stock build with the exception of a TF 2 kit in valve body. I have build a dozen 727's and never encountered an issue like this.
Its felt kinda sluggish like it was dragging. Drove about 5 miles and slowed down for a car that was turning. When I accelerated the rear wheels locked solid for about a second and then it went on its way. Drove a few more miles and got to a place where I could safely test it. The lockup occurred several times again then I parked. it.
The only thing I can think of was the rear clutch pack clearance was rather tight. I should have ordered the thinner plates but in haste to get the car ready for a show I just went with it. Tried a variety of selective snap rings but it was still not where I wanted it.
Any thoughts on how to proceed? I was thinking about swapping the valve body out first to rule that out before pulling the trans. I have a nice turbo action reverse manual I can throw in it.
 
Even if the rear clutch was locked it wouldn't behave like that because the forward clutch is engaged in all forward gears. You just woudn't have reverse and it would go forward in neutral. Sounds like the band is applying during third. I would remove the valve body and double check the work. Did you reassemble the servo correctly? But ya try the other valve body for a quick test.
 
Sounds like an intermittent cross-feed from another circuit.
Or a cast-ring failure between the hi-drum and the forward clutch; but that's a stretch.
You can catch all that on an oil-pressure test. Maybe on an air-pressure test as well.
 
As Cudafacthackjob said the rear clearance shouldn't do that in forward gears. If it's not trying to pull in neutral the rear clearance is ok. If it is pulling a slight amount in neutral it'll probably wear in in a few hundred miles and stop doing it. I'm not exactly clear on when it's happening to you so if you could go out on a road where the traffic is low (or none) and stop and run it though each gear and explain exactly when it's happening (such as on the 1-2 shift or the 2-3 shift or only when it downshifts to 2 or 1) I might be able to help more.
 
Check ur band adjustment. What is it? How many springs in the front clutch pack? How many springs in the front servo? Did u put the restrictor plug in the case? Did u put spacer in the rear servoand the big spring? Did u install the new manual valve and adjust it properly? Did u drill the valve body in 2 places. Tell us Kim
 
MoparMike1974 said:
Rebuilt my 727 and now it seems to be binding in two gears occasionally. Mostly stock build with the exception of a TF 2 kit in valve body. I have build a dozen 727's and never encountered an issue like this.
Its felt kinda sluggish like it was dragging. Drove about 5 miles and slowed down for a car that was turning. When I accelerated the rear wheels locked solid for about a second and then it went on its way. Drove a few more miles and got to a place where I could safely test it. The lockup occurred several times again then I parked. it.
The only thing I can think of was the rear clutch pack clearance was rather tight. I should have ordered the thinner plates but in haste to get the car ready for a show I just went with it. Tried a variety of selective snap rings but it was still not where I wanted it.
Any thoughts on how to proceed? I was thinking about swapping the valve body out first to rule that out before pulling the trans. I have a nice turbo action reverse manual I can throw in it.
Click to expand...


Just off the top it sounds like a shift bind where two gears are applied at the same time for a second or two, because a gear is applying while before the last one lets go.
It happens frequently with the TF2 kit install when shifting automatically, and there are ways to deal with it as some have hinted at already. (it's called shift overlap)
Tracy can help with a lot more info if he knows exactly what it does and when it does it.
 
oldkimmer said:
Check ur band adjustment. What is it? How many springs in the front clutch pack? How many springs in the front servo? Did u put the restrictor plug in the case? Did u put spacer in the rear servoand the big spring? Did u install the new manual valve and adjust it properly? Did u drill the valve body in 2 places. Tell us Kim
Click to expand...

Bands are 1.5 turns I think, whatever the transgo manual said. I think there were 5 or 6 springs in the clutch pack. Put them back the same way they came out. Dont remember what is in the front servo. Yes, installed restrictor in the case. New manual valve installed and adjuster per instructions. Drilled the valve body per instructions as well.
I have installed 3 or 4 of these kits in the past and this is the first time I ever had an issue with one.
I have my other car coming out of paint shop this week so this one is going on the back burner for a while. I guess my next step will be to swap in a known good valve body and go from there. Weather has turned cold here so it may be a while before I can get back to this.
 
MoparMike1974 said:
Bands are 1.5 turns I think, whatever the transgo manual said. I think there were 5 or 6 springs in the clutch pack. Put them back the same way they came out. Dont remember what is in the front servo. Yes, installed restrictor in the case. New manual valve installed and adjuster per instructions. Drilled the valve body per instructions as well.
I have installed 3 or 4 of these kits in the past and this is the first time I ever had an issue with one.
I have my other car coming out of paint shop this week so this one is going on the back burner for a while. I guess my next step will be to swap in a known good valve body and go from there. Weather has turned cold here so it may be a while before I can get back to this.
Click to expand...
1.5 turns on the bands and only 6 springs in the front clutch usually spell disaster when it comes to the 1-2 and 2-3 shifts cleanliness. In other words it is most likely binding up on the shifts and if it is it will not last long at all before it trashes everything. Unless your running a 5.0 front servo lever (a big no-no with a stock type valve body IMO) you should have the front band out at least 2 turns. Same for the back band. What is the ratio on the front servo lever in the trans? I always use a bare minimum of 10 springs in the front clutch pack too to avoid shift overlap. First thing I'd do it check and adjust the bands at 2 turns out from 72 inch lbs on the rear band and 2-1/4 out on the front band and test drive it
 
Its not the 5.0 lever, used the stock lever. Not sure what ratio it is. I will try adjusting the bands before dropping the pan.
 
I finally got a chance to pull this trans and its not looking good. Came apart good until I got to the rear drum and the output shaft was stuck hard in the rear support. I got the shaft out by hitting it with a brass punch, shaft looks ok and no scoring.
Now I cant get the rear drum out. It appears the over running clutch is the culprit. Its come apart and locked everything up. Any suggestions on how to get out the rear support and drum? Im really hoping to save this case since its numbers matching 340 car.
 
Cut out the back of the drum at the bottom center of the case about the dize of a penny. That should expose the setscrew. Remove it and the sprag should pull forward with the drum.
 
I was able to tap the rear support out using a large socket and dead blow hammer. Not sure what caused this sprag to go like this. Looks like the rear support was lacking lubrication too as the shaft was tight in it. Shaft is ok, rear support is trash. Luckily case is fine.
Now I need to decide how to put this back together. I will be doing a bolt in sprag, undecided on 4 bolt or 6 bolt. Im thinking about going with a billet rear support with bearing and the drum with bearing from coan.

20190209_143808.jpg


20190209_144819.jpg


20190209_144838.jpg
 
I found a sprag from a parts trans but cannot find a rear support anywhere in my stash. I should have a couple because I parted a couple that my friend left out in the rain years ago.
On a plus note, I found a nos mopar sprag race, spring and roller kit in the box.
 
That is a sprag failure. Always check the condition of the spring retainer fingers. They get bent, and I beleive reduced spring tension allows the inner race to migrate around, which allows a roller to jump to the next pocket, then two, then....... here is an impending sprag failure I found on disassembly. Check your case carefully for fractures around the outer race.

IMG_20170522_141808.jpg
 
d55dave said:
That is a sprag failure. Always check the condition of the spring retainer fingers. They get bent, and I beleive reduced spring tension allows the inner race to migrate around, which allows a roller to jump to the next pocket, then two, then....... here is an impending sprag failure I found on disassembly. Check your case carefully for fractures around the outer race.

View attachment 1715287340
Click to expand...
Note the fracture in my picture directly above where the two rollers share a pocket.
 
This was a fresh rebuild and failed within 5 miles. The sprag was inspected and was fine during assembly. I installed new springs and rollers. Im beginning to question the quality of the rollers, they came from rock auto.
The race did not spin in the case, it was nice and tight. No visible cracks in the case.
Everything in the trans looks great except for the sprag. Getting ready to order a 6 bolt bolt in sprag, roller rear support and valve body with low band apply.
 
I'd question the springs before the rollers. I've rebuild numerous 727's and never had a problem but I also do an oiling mod to help lube the sprague and output shaft support. Clean that case super good around the sprague and look it over with a magnifying glass to make sure their isn't any hairline cracks that aren't easily visible to the eye
 
You bought transmission parts from Rock Auto?
 
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