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Discussion Starter #1
Alright guys, looks like I got another one for you. I put the new vavle body in today, 1,2,d,n,r,p pattern. I have put the stage II transgo shift kit in there. It seems to shift pretty firm and fast, but the 2-3 shift has some problems. At really low rpm shifts, below 1K, the shift is good, as is it at shifts above 3K. However, between 1 and 3 K rpm shifts, the 2-3 shift will not catch right away. For a brief second, it sounds almost like i am revving the car in neutral, and then it proceeds to shift into 3rd gear. The weird part of this is that it is only generally at those specified rpms. The tranny looked good otherwise, with the only other thing I noted being the bands seemed a little loose. Is it possible that those are too loosely adjusted, because they are definitely looser than when I originally adjusted them? I dont think this is likely to be the culprit as the old valve body had a fine 2-3 shift. My only other thought was that the new vavle body has a bad 2-3 shift valve, but it seemed to be functioning fine when I overhauled it. There is one other strange occurance on the 1-2 shift. The shift quality itself is good, but it will squeal the tires on a straight line acceleration but not on accelerating out of a corner. Basically, I easily turn the corner to prevent sideways kicking of the car due to tire spin, and then proceed to get into the acclerator, and on the 1-2 shift, it will not squeal. Then, on straight line acceleration, while getting into the throttle the same amount, it will squeal the tires on the 1-2. Is there some sort of pressure buildup that accounts for this discrepancy? Anyways, that is not my biggest concern, as I would first like to get rid of the 2-3 problem.

Thanks for your help.
Dave
 
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In your C-4 the intermediate band has to release & then the high clutch pack takes over. The band may or may not be loose but I suspect either the piston seal in the clutch is bad(which I doubt) or your clutch pack is getting loose. Could possibily be a line pressure problem but the shift kit should take care of that. How many miles on the trans? Early or late? Could always adjust the band if you feel like it, don't cost nuthin'.
 

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Dave,

Try adjusting your bands again and re-test. Don't take any liberties with the specs...follow them exactly.

This is the later (67-up) valve body, yes?

Since the same pressure retracts the band piston that applies the reverse-high clutch to give you direct drive, if you have a sluggish clutch (whether because of worn seals or excessive clearance/wear in the frictions), you'll get some spin-up on the 2-3.

I never was able to get a manual/automatic valve body to perform adequately in the race car and finally opted to put a full manual shift kit in it. On a good day, the W would bark the Firestones on the 2-3....and that was with a trans which had close to 1000 runs on it..

Given the symptoms you described, start with verifying the proper fluid level, adjust the manual linkage, adjust the bands again, and test-drive. I would suggest disconnecting the kickdown linkage while testing but it's not necessary...
If you still have problems, it may be time to do more invasive diagnostics; this is where a trans service manual can help. Air checking the actuators and checking pressures are all part of the game...

Get back to us with any results or further questions....

Good luck!
 

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Did you replace the bands? I put a shift kit in my old 78 bird I had with a 351W and a C4. That think kicked butt and chirped at 2 and 3 until I snapped the old band. I never took the time to put in a new competition band in, I sold the car. If you did change the band did you soak it first for a half hour in trans fluid? If not you might have cracks in the pad.
 

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Discussion Starter #7
Alright--

Adjusted the bands, and on the first try, they were apparently too tight, as the car did not like to budge in either reverse or drive. I had followed the specs, but i loosened them up about 1/2 turn and then tried again. The car went into gears this time, and the shifts were decent. The 1-2 shift is relatively unchanged, and the 2-3 was about the same as well. However, while driving at say 40 mph, all of the sudden it seemed like i put on the brakes, and the car downshifted all the way to first gear. I did this one other time, so I suspected the kickdown lever had somehow gotten stuck. I came back, and tightened the band up about a 1/4 turn, and disconnected the kickdown lever. At first it seemed like something was holding the car back, but after the first shift or so, it started working normally. the 1-2 shift is as good of quality, and the 2-3 shift is fairly good. I only get run-up on the 2-3 when traveling very close to 30mph at the time of the shift, roughly 2k rpm. The sudden downshifting has not come back, so I am hoping that it was just the kickdown lever.

Any other ideas?
Thanks for your help

Dave.
 

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Discussion Starter #8
Ok guys. The sudden downshifting/braking problem has returned, so I guess the kickdown was not the culprit. The only thing that has changed is the bands, so I am going to try loosening them back up to get rid of the downshifting problem. I still cannot put a finger on the 2-3 shift problem. All I know is that none of these problems were present with the old valve body or before I messed with the bands. Now I am kinda at a loss on what to do, and the car is not very safe to drive as is, so I cannot road test it at higher speeds, because if it decides to do its downshift thing at 60 mph, I think the end result is going to be very ugly.

Ideas, random thoughts??? Anything would be somewhere to start from.

Thanks
Dave
 

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Discussion Starter #9
Ok, test drive #6 (+ or - a few)

Backed off the front band a good 1/2 turn (more likely to be greater than 1/2 turn than less) The sudden downshifting has gone away (I hope, fingers crossed) the shift quality has diminished a little bit since the adjusting of the bands. so now I am back to the 2-3 problem.??

Thanks
Dave
 

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If the 2-3 is good except within a narrow rpm range, I'd say it's likely related to either the control pressures created by the vacuum modulator and governor or to the scheduling valves in the valve body, specifically the 2-3 backout valve.

If you don't have a comprehensive trans service manual, now would be a good time..*G*

My old textbook from college covered a lot of theory and diagnostics, mostly on the C6's...the troubleshooting pages I've put up here are from it. Search my old posts and you'll find a treasure trove of transmission info..

Just to clarify, are you reporting shift quality when you shift the trans manually or when it shifts by itself in Drive range?

No fresh ideas at the moment but one never knows..*G*
 

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Discussion Starter #11
The shift quality I am reporting is generally when in drive. It is roughly the same for manual shifting, and I still get run-up if I manually shift 2-3. The braking effect returned on the last drive out, so I am at a loss there. I don't think the bands are that mal adjusted that it would be causing that. Is it possible that the valve body could be responsible for that too? Would it be worth a shot to try hooking the old valve body up and see what happens?

Thanks
Dave
 

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so I am at a loss there.

Sounds like a typical day for me....today I was trying to figure out how to put a 1000 lb tractor transmission housing into my horizontal mill to surface the turning brake locators without tipping the machine over...*G*

Describe your band adjustment procedure for both intermediate and low-reverse bands...
 

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Discussion Starter #13
As per the instructions for band adjustment with my shift kit, I tightened the bands down till snug with a short wrench, then backed off 1.5 turns on the front band, and 2 turns on the reverse band. Neither the forward or reverse would disengage and allow the car to drive, so I adjusted the bands down approximately 1/2 turn each, and then they both allowed the gears to work. I have since turned the front down another 1/2 turn to try and fix the braking problem. On both forward and reverse, the car hammers really hard when put into gear, and when the bands were tighter, that initial engagement was softer. The braking problem seems to be getting more drastic, but only occurs when the car is in drive. If I hold the car in second, and drive to about 40mph, which is generally where the braking comes in at, it will not happen.

Thanks
Dave
 

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Band adjustments....try snug with 1/4" drive ratchet or short wrench (spec is 10 lb-ft), then back 1.5 on intermediate and 3 on low-reverse. Be careful to hold the adjuster spud stationary as you tighten the locknut...

I'm betting your low-reverse band is dragging...it only holds the drum in manual low (the overrunning clutch holds it in Drive range) and in reverse...

That's it for tonight...*G*
 
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