transmission jumping out of gear

[james curl]

Under light loads or during coasting down to a stop my P-15 transmission jumps out of high gear.  If you use second to slow the car it to will jump out of gear.  I purchased a used transmission to replace my bad transmission.  After jacking the car up and placing 6 jack stands under the car, removing the front bottom cushion and the floorboard I was ready to start.  That is when I found the top two bolts backed out far enough that you could spin the lock washers and both bottom bolts were a full round louse.  I could move the tail shaft up and down.  I think that reversing the load on the drive shaft between driving and coasting was moving the input shaft causing it to disengage the slider ring that couples the two shafts.  I am considering just re-tightening the four bolts and button every thing back up.  Take it off of the jack stands and go for a drive to see if that was the problem.  If it is not than I have wasted a lot of energy taking it down and putting it back up on jack stands, and at my age I cannot afford to waste what little energy that I have.  Any and all comments are welcome, I need to solve this jumping out of gear problem so that I can get on to better things.

 

 

 

 

 

 

 

 

 

 

[Don Coatney]

The movement of the transmission could have been enough to allow the gear selector arms to pop out of gear. I suggest you snug the transmission up and go for a drive.

[james curl]

I am thinking of movement between the input shaft and the out put shaft as they are coupled together in high gear.  the input shaft should still be tight in the bearing in the crankshaft and the bearing on the input shaft at the transmission case should hold the input shaft in place causing the coupling between the two shafts to flex and uncouple.  I am hesitant to place the car back on the ground only to find that is not the problem.  Just jacking the car up and putting it on jack stands is all that I can muster in one day now.  My endurance level gets less every year now,  I always thought that at 78 almost 79 that I could still get after it all day long.  But old age is creeping up on me it seems to my disbelief.

[Don Coatney]

I fully understand James. My mind continues to make promises that my body cannot keep.

[Young Ed]

The movement of the transmission could have been enough to allow the gear selector arms to pop out of gear. I suggest you snug the transmission up and go for a drive.

 

I agree too. While you might cause yourself some rework if we are wrong you will certainly save a ton of work if we are right.

[james curl]

Well I did as Don C suggested, buttoned it all up and put it back on the ground, went for a test drive.  I have mixed news to report, it stays in high gear when coasting down from 40 to a stop, not so second gear it pops out every time after a couple of seconds.  This could be a shift rod adjustment and maybe not.  With mixed feelings I am contemplating putting it back up on jack stands and just replace the transmission with a used one I bought.  It has a 1953 build date stamped on the front flange and the fellow I got it from said he had it on the shelve since the sixties.  Going to rest a bit,read the mail and wait for it to get really hot outside before I continue with putting it back up on jack stands.

[DonaldSmith]

Try the shift adjustment first.  I think it's done under the hood, not under the car.   Nothing to lose. Meantime, take a break.

 

I plan my day with a young man's mind, but get old real quick when I try to follow the plan.   

[james curl]

Well I am having a hard time believing that the car is back up on jack stands, floor and bottom seat cushion out, back to the configuration it was two hours ago.  In the mean time I thumbed through the latest issue of Street Rodder and Hot Rod and read the letters to the editor which is usually the best part of the magazine.  Time now to clean up as I promised my 91 year old mother in law that while my wife was gone we would go get fried catfish for supper.  She walks down to the Senior Citizen Center every day and plays games until they close at 4:00pm.  Have to have her home before Wheel of Fortune comes on.  Well hopefully tomorrow will be another day and II can replace the transmission after checking one more time that the second gear selector is as far forward as it can go.

[Don Coatney]

Although it is hot I hope you are not in the flood plane and the catfish was not caught in your back yard.

[Ulu]

James, my original P-15 trans did the same from time to time. It would slip out of gear or I'd have to fiddle with the shifter to get it all the way into high.

 

It turned out I had 2 problems. The 2-3 shift fork was worn very thin on the fingers. The forged steel there had lost over 1/3 of it's thickness. I brazed it up and dressed the fingers down flat & smooth.

 

The second issue was the needle bearings between the input and output shafts, which are at the 2-3 syncronizer. They were shot, and the bearing surfaces on both shafts were brinelled. I dressed those surfaces down and turned out a custom bronze bushing to replace the needles. I replaced the bronze syncromesh rings with new ones, as well as the detents on the 2-3 syncro hub.

 

I put another 20,000 miles on that worn old trans before I bought my OD trans, and it always shifted like a dream.  

[james curl]

No Don, I am a long ways from the flood plane and we went to a Cat Fish Cafe which uses farm raised Cat Fish as do all of the Cat Fish cafes in Texas.

[Plymouthy Adams]

never did get the hang of hoeing catfish roe

[Ulu]

It's a tough roe to hoe....

[james curl]

Today disconnected the shift rods from the transmission arms.  The gear shift lever has more than enough travel in the second high range to get the selector in gear.  When working the shifter arm in the second/high positions the movement does not have a good solid feel like the replacement transmission does.  The replacement transmission has a real solid feel as the gears are coupled where as the one in the car does not.  This could all be in the shift box itself from wear. 

 

I am going to install a tandem master cylinder and re-plumb all of the brake lines and the three rubber hoses while I have the car up on jack stands to replace the transmission.  I replaced all of the rubber hoses in 2007 before going on my long trip, they are 8 years old and could stand to be replaced while I am doing the rest of the brake system.  I bought a Phoenix reverse bleeder to get all of the air out of the brake system I hope.  I will post back here when I have it all done and back on the ground drivable.  I plan on opening the transmission up at that time to see what is causing it to jump out of gear, I suspect it is the needle bearing between the input and main shaft allowing the two to move enough to uncouple when the load is reversed.

Edited June 5, 2015 by james curl

[Ulu]

A heavily worn pilot bearing or input main bearing is also a common cause of flaky shifting.

 

Changing the trans fixes the main input bearing, but if you haven't replaced the pilot bushing and throw out bearing, I'd surely replace those at trans swap time.

 

20 years ago I bought a Dodge flat-6 with trans from this guys cobbled up Desoto sedan. He said the engine ran great, but the clutch was shaky & the trans was slipping out of gear & was shot.

 

The trans internals were all serviceable, but what was shot was the pilot bearing. The dang thing was wallowed out nearly all the way to the flywheel   Also the throw out bearing was pressed on the collar rather crooked. All that was probably making his clutch foot vibrate like a Mixmaster. 

[Niel Hoback]

I think if it was mine, I would look for a broken detent spring or worn down or broken ball. One at a time, back out the big bolts at the front of the shifter cover and pull the spring out. Use a magnetic screwdriver to pull the ball out. Can be done in the car.