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REBUILT 727 HARSH SHIFT INTO REVERSE ONLY

HAHNAGON

Well-Known Member
Local time
4:21 PM
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Location
MOUNT VERNON, IN 47620
Ok....here it is....I am having a harsh shift into reverse from park or neutral. I have a 727 with 69 year stamps on it. It's been supposidly rebuilt before I got it. Fluid and filter looked new. I have dropped the pan multiple times and readjusted both bands to 72 in lbs and then 2 1/2 turns out. I put a new mopar deep pan, new mopar filter with extension on it, new mopar atf4+ fluid and I have a billet red accumulator with no spring and a rod that holds it to valve body, transgo tf1 shift kit(not manual) and i followed directions to a T .....twice to be sure. Fluid at full in idle. Correct idle? Always between 800-650rpm? I just feel like I'm seeing more band wear than expected collecting to magnets more than i like. Dark grey powder and fluid on magnets and a few very small flakes this last pan drop. Not putting very many miles on it all. Like 20 miles at most between pan drop inspections. Is the harsh reverse shift my issue, an issue at all or maybe not anything to be worried about??

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Take the blocker rod out from under accumulator piston and let the piston float. Do you have proper KD linkage, adjusted properly?
 
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Forward gears see reduced pressure until throttle pressure causes it to rise... Reverse sees full pressure at all times... Normal... If your getting an excessive clunk check the idle speed and check for excessive backlash in the rear axle...
 
Sounds like you don't have enough torque converter drainback. LOL.
 
Perhaps the low/reverse apply servo is sticking a bit and hits hard when it breaks free under higher fluide pressure in reverse?
 
Really doubt the harsh engagement is causing wear.....more like preventing wear.
 
Tourqe Flite rear servo pressures approach 300 psi in reverse unmodified. irst ; I wouldn't worry about the debris. Second; if the accumulator is blocked with a rod remove it. Third; you upped the line pressure with this kit. Is the adjustment as far backed out as possible? If not you can loosen the spring tension on the adjuster screw. Forth; pretty sure you don't shim the low/ rev/servo piston with the TF1 kit. If you did you can remove the shim. Bottom line is with a stock or close to stock converter you will "feel" engagement more. If it was a loose conveter it wouldn't show up. I doubt if you'll hurt anything by leaving it alone. As a final note. Trans Go has a very good tech line. If you are still concerned, call them.
Doug
 
Adjust the rear band to 2 turns or even 1.75 turns. The loose rear band will really make it hammer into reverse. And as noted earlier and slop in the rear gears or axle gears will just compound the issue. Kim
 
Forward gears see reduced pressure until throttle pressure causes it to rise... Reverse sees full pressure at all times... Normal... If your getting an excessive clunk check the idle speed and check for excessive backlash in the
Adjust the rear band to 2 turns or even 1.75 turns. The loose rear band will really make it hammer into reverse. And as noted earlier and slop in the rear gears or axle gears will just compound the issue. Kim
I forgot to mention that I rebuilt the entire 8 3/4 sure grip, added disc brakes. When I did this, I also put new 3.55 gears in it and set them up myself and installed green bearings. No slop there or with axles when I did that. The allen head pressure screw on vb is screwed all the way out, just like the instructions say.

Ughhh. I'm so tired of taking the pan off. I've tried and tried to use the mopar reusable plastic/rubber gasket each time but it always seeps atf somewhere. I finally got it to seal this last go around with the fel pro black composite gasket and mopar rtv on each of it. With that said......the harsh reverse engagement doesn't bother me all that much, but I'm really tired of passengers looking at me like I have a problem whenever I shift into reverse. Would tightening the band actually make it better or will it cause faster wear on the band? If it's not a problem, just tell me to drive the damn car and enjoy it!
 
I wouldn't tighten the band beyound factory spec. It'll drag causing more issues. Read post #7. Thats the best it's going to get. Been building them for over 40 years.
Doug
 
I have a billet red accumulator with no spring and a rod that holds it to valve body, transgo tf1 shift kit(not manual) and i followed directions to a T .....twice to be sure.

Get rid of the rod.
On page 7 of the instructions, did you do type 1 that removes the "cushion spring" or type2 that install a spacer that blocks out the "cushion spring"? Either way these will give you a harder thump.
 
I wouldn't tighten the band beyound factory spec. It'll drag causing more issues. Read post #7. Thats the best it's going to get. Been building them for over 40 years.
Doug
So I take it u know the rear band is adjusted to 2 turns and not 2 1/2 like he has it? After 40 years maybe u forgot the factory spec or the tras go spec? I know you’re the big dog on here but certainly u know 2 1/2 is way too much on the rear band. Kim
 
Ok. Thank you all for the comments. In case anyone is curious......here is what TRANSGO says about. They sent me this in an email. 2 pictures and a short story.

TransGo says....

"As for the harsh engagement it was just a very common and annoying issue on those, they were very prone to that. It's not going to hurt anything but if you want to make it softer you can do it.
I am assuming that the valve bodies you have don't have the "R" check ball we mentioned in the instructions. I have attached a screenshot here circling the hole in question. If you don't have a hole there you could make one yourself and go to about 0.060" and then add a 1/4" check ball in the pocket.
If yours already has a check ball and a small hole there you will have to make it smaller. To reduce the size of the hole you can use the method shown in the other image I am attaching here."

Robert

TransGo El Monte, CA
Product Support M-F 8:00 AM to 4:00 PM PST : (626) 443-7451

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Reducing Hole Size.jpg
 
I’ve never had to do that. How many clutches are in the front drum? What is the clearance? If u have less than .015 clearance per clutch that is part of the problem. Did u install the cupped orifice plug? Thanks. Kim
 
I’ve never had to do that. How many clutches are in the front drum? What is the clearance? If u have less than .015 clearance per clutch that is part of the problem. Did u install the cupped orifice plug? Thanks. Kim
Not sure on the clutches, but yes, I installed the orifice plug. I was wondering if it might be because of that plug. For some reason, my brain is telling me it didn't do that until after I put that plug in. But I can't remember. I've have had the pan off so many times, tried 2 valve bodies, etc, etc. It's easy to forget.
 
The kit supplies 600% more oil to the front drum. So u need the office control plug installed into the case. U need to adjust the rear band to 2 turns. Anymore that that and it will hammer into reverse. I too have did hunderds of torque flites so believe me if u want or totally ignore me. Your call. I still suspect u don’t have enough clearance in the front drum. Kim
 
Those that say it will not hurt anything are wrong, with high line pressures in reverse it will break the ear off the band, fold over the little link, blow the lip seal and break the band linkage. I like the fix transgo sent you. We used to make that hole 1/8" and drill a 1/16" hole in the rear servo. Snow plow trucks would come in with broken rear bands all the time. I set the front clutch to .075 and the bands to two turns, with a new b@m traveler converter those transmissions lasted for decades, as the front clutch wore you would have to pull that restriction out of the front clutch with 2 turns on the band, rather than tighten the band we pulled the restriction. I started leaving it out and putting more spring under the front servo. I want a tight converter with 2 turns on the front band and at least .075 on the front clutch to reduce heat build up, but with a tight converter reverse was a big issue.
 
Reverse requires the high/reverse clutch and the rear band to both be applied. At rest with no rotation of the input shaft you will never feel the clutch engage. So no adjustments to the clutch circuit will have any effect on harseness when engaging reverse. The restrictor is on the orifice feed to reduce fluid flow when engaging the clutch. Fold the band link? Bend the linkage? Not in this lifetime. Breaking the ear off the band? Only ever seen that when reverse was applied while the vehicle was rolling. Very rare. Think about this. Line pressure gets ramped up with race valve bodies all the time. Very few modify the valve body to reduce rear servo pressure. Nobody reduces front clutch pressure. Do they break rear bands and the associated hardware? No. The trick Trans Go told you is to slow fluid flow to the rear band.
 Doug
 
Rear bands break all the time in plow trucks around here, my own snapped just starting the truck and putting it in reverse cold, and it was a mopar band. It did have the high pressure relief drilled 1/8", and the pressure was set to the heavy duty step 1-5/16". The drilling of the servo was given to me by a transmission shop, his words were exactly " so we are not breaking things back here".
 
Rear bands break all the time in plow trucks around here, my own snapped just starting the truck and putting it in reverse cold, and it was a mopar band. It did have the high pressure relief drilled 1/8", and the pressure was set to the heavy duty step 1-5/16". The drilling of the servo was given to me by a transmission shop, his words were exactly " so we are not breaking things back here".
Exactly, plow truck. Run forward and whip them into reverse. Many times still rolling.
Doug
 
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