727 2-3 upshift VERY harsh

-
jimmyray

jimmyray

Well-Known Member
Joined
Jul 17, 2007
Messages
950
Reaction score
31
I recently had my Tranny & Torque COnvertor rebuilt at PTC in Muscle Shoals, AL. I had the tranny pulled out at a local shop, drove it 3 hours to PTC, and waited while the rebuilt it. I came back home and got it reinstalled, and all seems to drive OK, except...

The 2-3 upshift is extremely harsh. All else is normal.

Details:
727 Small Block
3000 torques convertor
Cheetah Manual Reverse VB, no engine braking in 1st.

When the car shifts 1-2, it is firm and surges forward like it is supposed to.

When it shifts 2-3, upshift is extremely harsh. It produced a loud, clunking sound, and seems to jar the entire car, almost like a brief stab on the brakes.

I talked to PTC, and they suggested I back the kickdown band, located outside the tranny, above the shifter linkage off 1/4 turn. I have now backed off about 5/8's of a turn, and it still does it, though not quite as bad.

I do not have an inch-pound torque wrench, so to reset it woul be by feel only.

Should I keep backing off the band, or am I barking uo the wrong tree?

Other Suggestions?

I will call PTC again tomorrow, but wanted your opinions as well.

THANKS!!
 
Just guessing but when people have their transmission rebuilt at transmission shop the shop more than likely have to do some fine tuning. So you are fine tuning it now. I would recommend getting a torque wrench and doing to the proper torque before you back off of the adjusting bolt. Then you will know for sure where you are at on the adjustment. I would still call them and bother them until the issue was resolved. It might be internal.
 
I wish mine shifted like that. The harder the shift the less heat produced thru slippage. Sounds like you have got the Race tune. You can also adjust the kickdown as it may be fooling the trans to think its shifting under wot.
 
mullinax95 said:
...fine tuning... It might be internal.
Click to expand...

I'm hoping it is just an exteral adjustement I can make. I do plan on bugging them, though!

Also, since it is a Manual VB, there is no linkage hooked up to the throttle, it is entirely a manual shift.
 
jimmyray said:
I'm hoping it is just an exteral adjustement I can make. I do plan on bugging them, though!

Also, since it is a Manual VB, there is no linkage hooked up to the throttle, it is entirely a manual shift.
Click to expand...

At what RPM do you shift from 2-3?
 
mullinax95 said:
At what RPM do you shift from 2-3?
Click to expand...

Differing speeds. The car is primarily a weekend streeter, with some strip duty. If I shift at WOT, it is still very firm, but a little overlap is noticeable. At less than WOT is where the harshness is most apparent. I've tried shifting anywhere from 1500 to 3500 rpm in partial throttle cruising, all very harsh.
 
jimmyray said:
Differing speeds. The car is primarily a weekend streeter, with some strip duty. If I shift at WOT, it is still very firm, but a little overlap is noticeable. At less than WOT is where the harshness is most apparent. I've tried shifting anywhere from 1500 to 3500 rpm in partial throttle cruising, all very harsh.
Click to expand...


I have never used a manual VB so I was wondering if that had to do with anything. Let us know what they say tomorrow.
 
The kind of shift your describing is not a good quality shift at all. It is definitely not a race type shift. What is happening is it is overlapping while shifting from 2nd to 3rd. (It's slow coming out of 2nd gear while 3rd gear is already engaged thus it's overlapping gears). That's why you said it feels like you momentarily stab the brakes. Previous belief is the harder the transmission shifts the less heat it will produce and the longer it will last. This is NOT TRUE. A good shift is firm and will probably even bark the tires (depending on the rest of the cars combination) but it never jerks or feels like you stab the brakes. When it overlaps like this it creates more heat than a stock trans. ever would and it's as hard on a transmission (and other parts of the drivetrain) as it is for an engine to spark knock. Did they put in a 5.0 kickdown lever? If so that may be the problem. It doesn't usually work good with a manual VB. A 3.8 or 4.2 is the highest ratio that should be used. If a 3.8 or 4.2 lever was used it's possible the VB is defective.

I have one other question. You said you waited while they rebuilt it. How long did it take? I have been rebuilding torqueflites for over 25 yrs. and have all the necessary tools to do it quickly but the quickest I can do one by myself is approx. 8 hrs. If they did it in a hour or 2 it sounds like they did little more than a quickie rebuild (change the clutch plates and steel plates and maybe, just maybe replace the seals) and didn't take time to check any clearances (which should always be checked) and replace all the necessary parts required in a proper rebuild such as all thrust washers and all bearings. Did they install a bolt in rear sprague? With no low gear braking they should have or it can let the clutch drum over run and explode with the power of a stick of dynamite.

Also if a trans. is rebuilt and a manual VB is installed there should be no fine tuning required if the trans was properly rebuilt and modified. Only a stock type valve body with factory kickdown linkage will need fine tuning.
 
fishy68 said:
Also if a trans. is rebuilt and a manual VB is installed there should be no fine tuning required if the trans was properly rebuilt and modified. Only a stock type valve body with factory kickdown linkage will need fine tuning.
Click to expand...

They (PTC) had it apart in about 10 minutes, but it took about 4 hours to get it back together. They installed a bolt-in sprag, and had to turn a couple of parts (drums, etc.) clean it up, and run it through their "dyno", a 6 cylinder engine with a couple of pressure hook ups and a drum attached to the tailshaft.

The valve body is the one that was in the tranny when I took it in. The tech mentioned it was pretty filthy inside, and took a good cleaning to get it in shape.

As far as I know, they used the lever that was in the tranny, which I assumed was stock, but I don't know for sure.

For the money and time I spent to drive it up there, 3 hours each way, I am not very happy at all. I will call them 1 more time, and adjust the kickdown band 1 more time, back off another 1/2 turn, but I am afraid this will affect the 1-2 shift quality at some point. FWIW, it did not do this before I took it in for service, but the convertor was slipping and leaking at the cracked hub pretty bad.

DSCF4019.jpg


DSCF4018B.jpg


Tranny Tagb.jpg
 
Hate to say it Jimmy but it sounds like you got a quickie unless they had 2 or 3 guys working on it. Funny how on the check sheet there's just a check next to the end clearance. I guess that just means it had some. LOL. Would be nice to know what that clearance is. Should be no more than .020 for a performance trans. When you call them tomorrow ask them if they checked it and what it was. Also ask them if they checked the clutch plate clearances and set them to what they should have been. It takes selective snap rings to set the clutch clearance. Also ask them if they shimmed the gear train clearance. It should be no more than .015 on a performance trans. Your correct in thinking backing the kickdown band off too much will affect the 2nd gear shift. Could also cause the band to slip and you probably know what that means. Not good.

If the VB was dirty (that wouldn't surprise me) and he took it apart to clean it maybe he put something back together wrong or left a check ball out. Just another thought.

Let us know how it turns out.
 
This is most probably not fixed by only adjusting the front band. This comes usually from a lot of front band/clutch overlapp from the valve body.

Jack up the car on the rearend and have a friend accelerate slowly, then shift to 2nd, then keep accelerating (you stand on the SIDE and watch the rear wheels!) and then have him shift to 3rd gear and see how the rear tires will almost or even stop completly before 3rd gear comes! This is the harsh shift you feel.

1. get rid of this valve body and get a low band apply manual valve body! Just last month a friend his 727 blew up with such a no low band apply valve body and ALMOST killed him! Here are the pics he send me:

http://home.datacomm.ch/6o4o/spragfail/

Next, get an orifice (from TF-2 kit) or even better, cut a 1/8NPT thread into the passage that feeds the front clutch. There you can install a plug with a hole in it (don't have my notes with me, but I thougth with a 0.14" hole to start with). For this you need to remove the valvebody. But as said, I would get rid of this VB anyway.

This will slow down the front clutch apply and decrease the overlapp you feel and see.

If the engine RPM's flare up, you need to increase the plug hole size, then the clutch engages to late. Just keep increasing till you got the perfect overlapp!

Michel
 
6o4o said:
This is most probably not fixed by only adjusting the front band. This comes usually from a lot of front band/clutch overlapp from the valve body.

Jack up the car on the rearend and have a friend accelerate slowly, then shift to 2nd, then keep accelerating (you stand on the SIDE and watch the rear wheels!) and then have him shift to 3rd gear and see how the rear tires will almost or even stop completly before 3rd gear comes! This is the harsh shift you feel.

1. get rid of this valve body and get a low band apply manual valve body! Just last month a friend his 727 blew up with such a no low band apply valve body and ALMOST killed him! Here are the pics he send me:

http://home.datacomm.ch/6o4o/spragfail/

Next, get an orifice (from TF-2 kit) or even better, cut a 1/8NPT thread into the passage that feeds the front clutch. There you can install a plug with a hole in it (don't have my notes with me, but I thougth with a 0.14" hole to start with). For this you need to remove the valvebody. But as said, I would get rid of this VB anyway.

This will slow down the front clutch apply and decrease the overlapp you feel and see.

If the engine RPM's flare up, you need to increase the plug hole size, then the clutch engages to late. Just keep increasing till you got the perfect overlapp!

Michel
Click to expand...

Welcome to FABO!

Wow! Thanks for the information. I don't have a clue what you are talking about but we need more people like yourself who knows his stuff. :-D
 
this is a very common problem for the 2-3 shift in full manual v/b transmission

my 727 full manual does the same thing when i shift from 2-3 unless im at or above 1/2 throttle

im no expert but it shouldnt have a harsh shift when you shift from 2-3 at 1/2 throttle
 
Mine does the same thing. Damn thing feels like its going to knock the glass out of the car at 1/2 throttle.

Thank god my 727 is going back to auto valve body....
 
if you have a manual valve body & its doesnt have a harsh shift when shifting from 2-3 its so awesome!!!!!!

i just took the dart for a drive and i gave it 60% throttle shifting from 2-3 & it was so smooth & at the same time firm/positive just like the 1-2 shift!!!!
 
I know Im necroing this thread, but was there any resolution?
I currently have a TCI drag race trans doing the same thing.
 
How many are saying to themselves, "Yup, this is why I rebuilt it myself. I know what's in it and I got off super cheap!"
 
6o4o said:
This is most probably not fixed by only adjusting the front band. This comes usually from a lot of front band/clutch overlapp from the valve body.

Jack up the car on the rearend and have a friend accelerate slowly, then shift to 2nd, then keep accelerating (you stand on the SIDE and watch the rear wheels!) and then have him shift to 3rd gear and see how the rear tires will almost or even stop completly before 3rd gear comes! This is the harsh shift you feel.

1. get rid of this valve body and get a low band apply manual valve body! Just last month a friend his 727 blew up with such a no low band apply valve body and ALMOST killed him! Here are the pics he send me:

Index of /6o4o/spragfail

Next, get an orifice (from TF-2 kit) or even better, cut a 1/8NPT thread into the passage that feeds the front clutch. There you can install a plug with a hole in it (don't have my notes with me, but I thougth with a 0.14" hole to start with). For this you need to remove the valvebody. But as said, I would get rid of this VB anyway.

This will slow down the front clutch apply and decrease the overlapp you feel and see.

If the engine RPM's flare up, you need to increase the plug hole size, then the clutch engages to late. Just keep increasing till you got the perfect overlapp!

Michel
Click to expand...
The orifice mod is in the Carl Monroe book.
 
If they didn’t install a 5.0 lever for the front servo, then that’s part of ur problem. U will need to adjust the front band to 2 1/2 turns from snug with short wrench if u don’t have an inch pound torque wrench. Torque is 72 inch pounds then back off band 2 1/2 turns the tighten lock nut. Kim
 
Last edited:
oldkimmer said:
If they didn’t install a 5.0 lever for the front servo, then that’s part of ur problem. U will need to adjust the front band to 2 1/2 turns from snug with short wrench if u don’t have an inch pound torque wrench. Torque is 72 inch pounds then back off band 2 1/2 turns the tighten lock nut. Kim
Click to expand...

My ex partner built our transmissions back in the day, he used to adjust our 727 front band to snug, and back it off 2 turns. I am not a trans man, but I don`t think I`d back the band adjustment off to try to soften the shift for any reason.
On a side note, my currant 727 is fully automatic, and slams the 3 rd gear shift so hard and fast it makes me think its going to break something. I adjusted the aftermarket kickdown looser almost an 1/8', but was afraid to go any further. It helped a small amount, and isn`t bad if I`m accelerating some, but still slams too hard if not accelerating, like in traffic. Will probly be fine at wot .
 
You must log in or register to reply here.
-

Back
Top