727 issue i think?

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RobertP

RobertP

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abbreviated story. car sat for a year with the engine apart getting heads ported new cam and all new interior.

now running again and when under power shifts great. when just being easy on the throttle and shift from first to second goes perfect, if i stay in second just easing on the throttle it will begin to for a lack of a better explanation feel like i am applying the brakes. shift into third and it frees up and back to normal? what the heck is going on? normally i never cruise in second for any extended period of time but this doesn't seem right to me.

trans specs. 727, redline clutches and bands, bolt in sprag, cheetah reverse manual valve body, 3500 stall turbo action converter. engine 416, rear 8 3/4 3.91 gear.
 
There are issues manually shifting a 727 into third from second that are covered in shift kits usually, that mentions shift overlap caused by the band not releasing before third takes hold.
The simplest reason for this could be linkage adjustment in case it's part way into or out of another gear, or if that isn't it you might try raising the line pressure a little and see if that does it. (higher pressure is why it doesn't do it using more throttle)
Line pressure (or throttle pressure) is adjusted with the linkage at the carb so that it shifts a little later in full auto mode.
 
with the manual valve body there are no adjustments on the carb linkage for throttle pressure.

i have checked and rechecked my shifter linkage for going in and out of gear and all seems right. went as far as to replace the shifter cable as well. it shifts into second and pulls hard with no issues when at wot. this is just at slow cruising when it feels like it is dragging. video at wot thru second.

[ame]https://youtu.be/XiHcu_3SAUg[/ame]
 
no i start all burnouts in second and shift to third to finish. has a bolt in sprag already though.
 
This is news to me... in my dragster burnout was in 2nd... why would a street car do a burn out in 2nd and not start in 1st? Im curious...dont want to hurt my trans... if its bad im glad i stmbled on this thread...
 
yay i learn something tonight... whats the issue is it a 727 reverse man issue ...727 in general? edumacate me...
 
nice..... as for your issue, residual on brakes? or sure its a trans issue... car was sitting, something get frozen up in braking system....?
 
tarvin890 said:
This is news to me... in my dragster burnout was in 2nd... why would a street car do a burn out in 2nd and not start in 1st? Im curious...dont want to hurt my trans... if its bad im glad i stmbled on this thread...
Click to expand...

see the sticky at the top of the trans sub forum that says 727 exploded or something similar. most trans catastrophic failures are from catching traction in first and rolling the sprag.
 
almost lookis like the brakes are in a drag causing the shaking...my thoughts on it.. probably wrong, but ive had a brake not fully disengaged drove fine as they heated.... well im sure you get the picture
 
this is just at slow cruising when it feels like it is dragging.
Click to expand...


Are you sure it's the trans? A brake isn't hung up or something, is it?


I had a Dana rear one time, and the ring and pinion was getting bad (didn't know it) and it felt like something was holding me back.

I finally figured it out when the R&P ended up in pieces.
 
tarvin890 said:
nice..... as for your issue, residual on brakes? or sure its a trans issue... car was sitting, something get frozen up in braking system....?
Click to expand...

brakes are new front and rear. just actually installed the front with a disc conversion. this only happens in second gear. free rolls fine in first and third with no issue.
 
hmmm 2nd only.... im out... lol where are the trans experts when you need em....let us know.... i want to stay with my brake issue thoughts... but i dunno....subscribed..
 
Bad Sport said:
Are you sure it's the trans? A brake isn't hung up or something, is it?


I had a Dana rear one time, and the ring and pinion was getting bad (didn't know it) and it felt like something was holding me back.

I finally figured it out when the R&P ended up in pieces.
Click to expand...


i believe its narrowed down to the trans. brakes are new. never drags or feels like I'm being held back in first or third, and as soon as i shift into third from second when its doing this it frees right up and rolls effortlessly. i can let off the gas pedal and actually feel the car being held back but as soon as i shift into third it frees right up.
 
Robert what your experiencing is shift overlap. Like Trailbeast mentioned it's when the front band isn't fully released and the front clutch applies. If it's as noticeable as you describe it'll shuck a trans fast so get it fixed quickly. There are several reasons it can happen.

1. the front band adjustment and/or front clutch clearance is too tight

2. incorrect front band apply lever. Manual valve bodies generally recommend a specific lever ratio to use. The higher the ratio the slower the band releases

3. not enough springs (or real light springs) in the front band servo. This can be compounded by the use of a flex band in the front.

4. low spring count or weak springs in the front clutch pack. For a perf build I replace them with new and use 12

Do you have the specified front band apply lever that the manual VB calls for? If so check the front band adjustment. If it's correct try backing it off 1/4 turn a time or two and see if it helps. Do you have any idea how many springs were installed in the front servo? That affects how quickly the front band releases so if only 1 was installed and everything else I mentioned fails try installing a second. If the trans has a flex band in the front they are a little slower releasing than a solid band is but generally you can work around it by installing the stiffest front servo springs you can find.
 
Since the tranny is locked in second( assuming your adjustment is spot-on), then I would hazzard that the VB is leaking pressure into either the L/R circuit or the direct circuit.It seems the tranny is trying to catch two gears at once.
I would perform an air test to prove the actual in-the-case circuits are ok(the problem could be the front gasket, or even the pump house), and if those are ok, then it would have to be the VB.
 
fishy68 said:
Robert what your experiencing is shift overlap. Like Trailbeast mentioned it's when the front band isn't fully released and the front clutch applies. If it's as noticeable as you describe it'll shuck a trans fast so get it fixed quickly. There are several reasons it can happen.

1. the front band adjustment and/or front clutch clearance is too tight

2. incorrect front band apply lever. Manual valve bodies generally recommend a specific lever ratio to use. The higher the ratio the slower the band releases

3. not enough springs (or real light springs) in the front band servo. This can be compounded by the use of a flex band in the front.

4. low spring count or weak springs in the front clutch pack. For a perf build I replace them with new and use 12

Do you have the specified front band apply lever that the manual VB calls for? If so check the front band adjustment. If it's correct try backing it off 1/4 turn a time or two and see if it helps. Do you have any idea how many springs were installed in the front servo? That affects how quickly the front band releases so if only 1 was installed and everything else I mentioned fails try installing a second. If the trans has a flex band in the front they are a little slower releasing than a solid band is but generally you can work around it by installing the stiffest front servo springs you can find.
Click to expand...

This is what I was afraid was going to be the issue. I purchased the valve body and converter and bolt in sprag then took the trans a very well know trans builder in my area he took care of the assembly knowing what the car was going to be used for. It was built probably 10 years ago and probably less than 3000 miles on it since. It was spot on when I pulled the top end apart a year ago. Now that it's running again I've noticed this. I will adjust the linkage again to verify. Any tricks to that other than having someone in the car while it's on the lift and me adjusting it on the trans?
 
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