727-904 REVERSE SLAMS HARD WHEN SELECTED

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coalman

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I have posted this before, I have had it back to the shop, and it is going again. It bangs into reverse very hard when selected, the shift lever moves it there just fine, forward gears are fine. Are there some experts out there that know what is going on? I would really like to get this resolved, I am worried about really damaging the trans. Thanks a bunch
 
All I can speak of is my own. Hard engage of reverse only happens after it sits, and it sits for weeks at a time. The torque converter leaks down. The front pump in the trans doesn't run in park so refilling the torque converter wouldn't happen for a very long time. If I go straight from park to reverse I get a 1.5 second delay then bam, I've got reverse. Soooo I learned to first go straight from park to neutral, give it a few seconds to fill the converter, then to reverse. No bam.
 
All I can speak of is my own. Hard engage of reverse only happens after it sits, and it sits for weeks at a time. The torque converter leaks down. The front pump in the trans doesn't run in park so refilling the torque converter wouldn't happen for a very long time. If I go straight from park to reverse I get a 1.5 second delay then bam, I've got reverse. Soooo I learned to first go straight from park to neutral, give it a few seconds to fill the converter, then to reverse. No bam.

Agreed.. My mechanic stated the exact same response regarding my 340 Duster/727 tranny. After starting engine, go to neutral for a min, then drop into drive once or twice before going into reverse. This is especially so if you have a shift kit.

This gets the fluids moving around. Old cars are like old guys, things need a bit loosening up before kickin' it in gear..
 
Old Dodge trucks are plagued by this too. If the trans is already modified to pump in park, then It's a combo of slop tolerances in the driveshaft (slip joint), and the pinion and ring gear. IMO, it's annoying, but harmless.
 
Old Dodge trucks are plagued by this too. If the trans is already modified to pump in park, then It's a combo of slop tolerances in the driveshaft (slip joint), and the pinion and ring gear. IMO, it's annoying, but harmless.

I had a trans with modified valve spool that pumped in P.
Iwarmed that baby up on a -15 degree day the last 10 minutes at work.
Left, put it in reverse after kicking down high idle, backed up normally, put it in drive, and at that moment the rear clutch pack welded.
No more reverse...only ever forward.
That was a fun February.

I'd much rather have the slow fill soft engagement, but then I always backed into garages in Chicago so I can't think of when I would have had a car sit for a long time that I would be first be backing up...
Never, I reckon.
 
If there is no spring in the accumulator bore it can make this happen, or make it worse.
You could put an orifice in the rear servo oil feed to slow it down also.

Of course this assumes you are not idling at 1,200 RPM's when in neutral. :D

TF.jpg
 
Just got out of the car and followed your instructions, it made a BIG difference!! It goes into reverse a lot better, very close to how it goes into drive! Thank you all very much... I have another question how long can the car sit without having to do this, or is this on the first start of the day every day??? Thanks
 
Just got out of the car and followed your instructions, it made a BIG difference!! It goes into reverse a lot better, very close to how it goes into drive! Thank you all very much... I have another question how long can the car sit without having to do this, or is this on the first start of the day every day??? Thanks
I would take the min or so everytime. Nothing to lose!
 
Just got out of the car and followed your instructions, it made a BIG difference!! It goes into reverse a lot better, very close to how it goes into drive! Thank you all very much... I have another question how long can the car sit without having to do this, or is this on the first start of the day every day??? Thanks
I don't have knowledge on all the variables related to torque converter draining/fluid leveling. We didn't this problem with our daily drivers back when.
 
Agreed.. My mechanic stated the exact same response regarding my 340 Duster/727 tranny. After starting engine, go to neutral for a min, then drop into drive once or twice before going into reverse. This is especially so if you have a shift kit.

This gets the fluids moving around. Old cars are like old guys, things need a bit loosening up before kickin' it in gear..
I got this same advise from a trans builder who was a Mopar dealer transmission guy back in the day. His advise was the same, get it off high idle, pull it into drive, then into reverse. No bang going into reverse. He said that this was a major cause for the lugs breaking off the reverse bands.
 
Redfish, I agree, growing up my Father had all Chrysler products with Torqueflite transmissions and I drove a lot of them, they never had this problem. Again, thanks to everyone for the input...
 
It is like said above a good thing to do for all mopar trans ... even my ram 2500 with 240k diesel ... i have plowed snow for several years and pulled my trailer all over and still original trans ... i warm up in neutral all the time since new .... it prevents wear as it gets the fluids moving ...
 
Pardon me here, but will this also affect normal shift points, and passing gear kick down? I have not had an automatic Mopar in years, all 4 speeds and one six speed which I totaled...
 
Is there a modification to the trans that can fix this, and if so, should a transmission shop know this??? Thanks
 
Is there a modification to the trans that can fix this, and if so, should a transmission shop know this??? Thanks

When you get right down to it, there may be a variety of things causing the banging from the tranny to the wheel bearings. A little bit of wear from the slip joint, u-joints, ring and pinion, wheel bearings.. all together can contribute to the banging. Grease EVERYTHING. Some have installed a zerk fitting on the slip yoke on the rear drive shaft to keep it well lubed.

Have you tried jacking the rear in the air and moving one of the tires forward and backward to see if you hear or feel any play in the drivetrain. I would do it before considering any transmission possibilities.

Just sayin..
 
Thanks to you all.. I am going to print this out and take the info back to the transmission shop and cuss and discuss, I will cut out all your forum info... Thanks a bunch..
 
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