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Problem in the drivetrain, I think ... PB 904, 7.25
https://slantsix.org/forum/viewtopic.php?f=20&t=63565
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Author:  slantvaliant [ Sun Apr 28, 2019 6:12 pm ]
Post subject:  Problem in the drivetrain, I think ... PB 904, 7.25

Sorry - long post. Need help with the diagnosis.

Summary: Something went shhhhhBANGjerk...jerk.....jerk.....jerk.... and I don't know what it was. I'm thinking transmission. Ideas?

Car: 1964 Valiant with a pushbutton 904 and a '76 225 (Super Six, HEI, etc). Disk brakes up front, stock rear drums. 2.94 ratio 7.25" open rear end. Aftermarket AC. Aluminum radiator with internal transmission cooler.

The Story: This was to be the first big out-of-town trip with this engine. The car has been running well for up to 40-50 test miles at a time on the freeway. I was carrying more baggage than usual, but nothing excessive. I headed out before 9:00 AM on a really nice Friday morning. Did not need the AC. I cruised at various speeds to see how it felt. The exhaust booms a little around 60-65, but it's better at 70-75. Coolant temperature and oil pressures looked good.

I was just cruising at 40MPH through a town 40 miles from home, and noticing how smooth that particular section of pavement was, when shhhhhBANGjerk...jerk.....jerk.....jerk....
The initial shhhhh had me thinking a tire was going down, or maybe a refrigerant leak. The BANG ended that line of thought.

Roadside Checks:
No clanging as I pulled off the road, just intermittent jerks, like a wheel or two binding or locking up briefly. No odd noises when parked. The engine ran smoothly until I shut it down. Tires are good. Nothing hanging under the car. Nothing pouring out. No smoke. No debris under or behind the car, on on the street where it went bad.
The engine restarted easily, sounded normal.
Transmission fluid was at a normal level. It was a translucent black, maybe a little purplish, not as red as it was earlier in the week. No chunks were noted.
AAA and a flatbed got the car home without any more drama. The wheels seemed to rotate OK as the car was winched up the ramp. I swapped cars and went on my way.

Diagnostics at home:
The front wheels rotate normally, with normal disk-brake sounds as they turn. The left front wheel bearing might be a little loose.
With transmission in neutral (N button in, lever up), one rear wheel off the ground, the wheel will only rotate a little in either direction, then stops solidly.
With both rear wheels off the ground, turning one wheel turns the other in the opposite direction. Normal. Effort required varies as you turn the wheel. Chocking one wheel stops both, as above. Not normal. The drive shaft does not turn during any of this.
Removed the driveshaft. (Note to self: Ball and trunnion boot is shot.) Now, with both wheels off the ground, the differential seems to be working normally for a well-worn 7-1/4" open rear end. Some slop, though.
With the transmission in neutral, I can't rotate the transmission output shaft flange by hand, or with a short pry bar (gently applied). Can't feel any movement.
Started the engine. Flange does not move in neutral. Put in drive - flange rotates. Put in reverse - flange turns the other direction. So, the parking pawl isn't engaged. I don't think it could do what happened, but I had to check.
The transmission fluid concerns me.

Thoughts?

Author:  Charrlie_S [ Sun Apr 28, 2019 6:38 pm ]
Post subject:  Re: Problem in the drivetrain, I think ... PB 904, 7.25

When the 76 engine was installed, did you install a reducer bushing in the crank, for the early converter?

Author:  SlantSixDan [ Sun Apr 28, 2019 6:57 pm ]
Post subject:  Re: Problem in the drivetrain, I think ... PB 904, 7.25

»waves hands over crystal ball«

I see…in your future…a transmission overhaul or replacement. The particulars of exactly what went bang will be revealed once it comes out in multiple pieces.

Author:  slantvaliant [ Mon Apr 29, 2019 7:49 am ]
Post subject:  Re: Problem in the drivetrain, I think ... PB 904, 7.25

Charrlie_S wrote:
When the 76 engine was installed, did you install a reducer bushing in the crank, for the early converter?


Yes, I did.

SlantSixDan wrote:
I see…in your future…a transmission overhaul or replacement. The particulars of exactly what went bang will be revealed once it comes out in multiple pieces.


Yeah, that's what I'm getting. Just trying to do my homework before I dive in. The more you know ...

Author:  Dart270 [ Mon Apr 29, 2019 7:52 am ]
Post subject:  Re: Problem in the drivetrain, I think ... PB 904, 7.25

Sure sounds like the trans, but I do not have a clue what it could be in particular.

Lou

Author:  sixinthehead [ Mon Apr 29, 2019 12:32 pm ]
Post subject:  Re: Problem in the drivetrain, I think ... PB 904, 7.25

Rear pump perhaps?
Since whatever died is dragging the output shaft, that is my best guess.

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