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1978 Mopar 727 Transmission Problem
03-05-2008, 05:52 AM
My very first post and I have a major problem. First off, Thank You! for participating and making such a fine forum here. This is by far the largest forum I have ever seen, no doubt. Anyway, my problem. I have an Apollo Motorhome that is really nice for it's ripe (1978) old age. So here is what happened. Dad figured the motor home needed moving to a shady spot in the yard. I stood outside while dad moved the MH and just before the MH came to a complete stop dad accidently put it in park. The motorhome was going real slow but a lot of suddenly stopping mass is a bad thing at any speed. I heard a loud "Pang" sound like the drive shaft was suddenly struck with a hammer. Dad had shut the engine off and was looking at me in shock from what had just happened. I crawled under and checked the drive shafts and U joints for damage. Saw no damage so told dad to start it up and try moving the thing again. Dad started it up and put it in drive and nothing happened, no movement. The motorhome wouldn't go forwards or reverse. So I got under the motorhome to listen to the drive shaft yoke for a slipping or grinding noise. I didn't hear anything grinding or slipping so I figure the teeth on the output shaft or in the yoke are OK. I have narrowed it down to the problem being in the transmission. So, what could have happened to my transmission? I am somewhat thransmission knowledgable and have installed shift kits and such before but this is my first big Mopar to tinker with. Any help would be greatly appreciated.
P.S. The local transmission shop won't tell me anything. They just say bring it in or bring it on by. Easyer said than done.
03-14-2008, 04:59 PM
Im no 727 expert, but I know they are pretty hard to kill. I have also heard that same 'pang' myself. So Im going to make a couple of guesses. The parking pawl may have gotten snapped off - and the loose pieces are in the way, so the tranny wont move. Or the shifter cable may have been 'kinked' when the parking pawl was thrown back away from the toothed ring & forced the shifter mechanism to move too.
Can you tell a difference when you go from being in Park or Neutral into drive or reverse? That is, does the engine slow down, indicating the tranny has really shifted into a gear? If the engine doesnt change speed, I would think the tranny still believes it is not in gear. If the engine does slow down - I would suspect the broken piece of the parking pawl is in the way.
If you watch the small lever that is moved by the lower end of the shifter cable; as someone moves the shifter lever (on the dash or wherever it is) from park down into "L", does the shifter shaft also move. Not just the little lever, but the shaft that it clamps to on the side of the tranny? You may need to clean lots of crud off to see this.
I have had the shifter cable 'kink' on my dodge based motorhome with the 727 tranny. The cable gets stiff from old age, and the kink occurs behind the dashboard at the top end of it - more commonly in chilly weather. I was able to remove the cable and more or less undo the kink & to free it up with some 3 in 1 oil (but got a new cable later anyway). During the time it was kinked, the shifter lever could point to reverse - but the tranny was not in any gear.
When you push the lever down from park into drive/2/L, you are pulling on it. When you move it back up into 'park' you are pushing on it. With mine kinked - moving the lever into 'park' left the transmission out-of-gear, but still able to roll down the slight downgrade of our driveway.
You might want to go to www.allpar.com. down the opening page is a search feature. Do a search on 727 or A727 or torqueflite (what the tranny was called in cars and pickups or loadflite (what it was called in motorhomes). Tom Hand's guide is one of the search results, and there are others. You may see your problem discussed.
The next step might be to drop the pan and look for any cracks or distortion in the mechanism at the bottom of the shifter shaft. Over the years 727s have been put into park while slowly moving - thousands of time. Usually with no damage other than a few flakes of metal being found in the pan stuck to the magnet that is usually there.
In the event you do need to drop the tranny and fix something, you will find the 'master rebuild kit' for the 727 is one of the least expensive around. Any other 'hard parts' you may need will likely be easy to get. The hardest part about dropping a 727 is that it weighs about 160 lbs & will be dirty. One gent who rebuilt his (cause it needed new seals mostly) said it wasnt as challenging as it was to rebuild the thermoquad carburetor his engine had.
I have taken a couple of them out, from motorhomes that were going to be boneyard, because I knew the 727's still worked and wanted to have extras. But the original 727s in my two 1972 Winnebagos havent worn out yet. One of them is past 100,000 miles, works fine, just seeps oil from its shiftr shaft seal. I have had to replace the lines to the cooler in the bottom of the radiator.
Be sure to check the fluid level often enough. The fastest way to burn up a 727 (possibly the only way) is to run it low on fluid!
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