Projects Mild custom '51 Pontiac Chieftain

I had the replacement governor sleeve assembly soaking down in Chem-Dip.

That got the majority of the old dried up oil and dirt from storage off.

Then went to town scrubbing up. Freed up both the pistons, both were stuck.
Ready to fit and test.

Phil

 

I have been following this from the start, fun to read, and love how you solve the problems you encounter.

 

Phil, is it advisable to hone the inside of the sleeve where the rings ride? I'm pulling down my hydra and there are definite marks, I can feel them but there are not ridges you can catch a finger nail on. What mine looks like:

 

I replaced the pin with a piece of spring steel of the correct size.
Fitted the unit and... Well, now reverse lockout works but it's still not shifting right. That brings the problem inside the case.

 

That still looks okay. Just keep the rings on the governor in the same positions but clean them thoroughly.

It is adviseable to cut the pin out and work the pistons free. Otherwise you'll be able to accidentally engage reverse on the move.

Phil

 

Car show tomorrow at the Rougarou Festival in town.


Made clean and shiny because it's going to be part of the show.

Phil

 

I need to follow this thread. I dig it

 

Went fuel up, on the way back stopped in for a chocolate malt. Just because.

Phil

 

Phil, I think you have life pretty well figured out.

 

Started out with a misty day. Proper Louisiana.

Part of the big shindig in town.

Pretty good turnout. Surprising how many people had questions about the car actually.

Phil

 

Oh my.

I have a wheel defecit.

Phil

 

There we go.

$61.20 later and I've got two new tires mounted and balanced. Nice.

Much better! They ride well too.

Phil

 

Car out and about, performing duties as Car. Went to the gas station and then went mow the grass here before the builders arrive to begin demolition of the concrete.

Had it up to 65 and it doesn't shake any more so one of the rear tires was either not round or not balanced. Either way, much better now.

Was having a think on the gearbox again, there's a possibility of a partial blockage on the oil feed to the valve block. I think I might have to drop both pans and have a poke about.

Phil

 

I pulled the pressure gauge point off the top of the gearbox yesterday and attached a rubber pipe. I started the engine and flushed 2 quarts of oil out. Apart from the general band dust in the oil it was clean.

I then connected my pressure gauge to it to check what it was doing.

It makes good pressure, the flow from the front pump is good. Hot, driving, you can see the dip from 60 to 45-50 psi when it selects a new gear, which then rises back up to 60.
However, the 8 cylinder variant should not run and hold 60psi line pressure at idle, it has a special circuit to reduce the pressure at off and light throttle positions, quickly increasing to the normal regulated 80psi. This was a result of adding more clutches to cope with the additional torque from the 8-cylinder engines. The extra clutches were snatchy at light throttle, so the fix was to reduce light throttle main line pressure, increasing it quickly as you put your foot down to a regulated 75-80psi.

The pressure regulator has 3 things inside to regulate pressure.
1, the main spring. This is meant to hold a minimum main line pressure of 60psi. This appears to be working correctly.
2, the reverse pressure boost piston. This is a large bore piston which is pressurized by engaging reverse and boosts the spring to raise the line pressure between 120-160 psi with reverse engaged to prevent the reverse cone slipping. This works.
3, the main line thottle valve piston. This is a smaller diameter piston which pushes on the back of the reverse pressure boost piston, which has no pressure on it at all in neutral or forward gears. Being a smaller diameter it imparts less force on the primary regulator plug and only raises the pressure slightly.

I need to pull both the pressure regulator and the main valve block out, possibly along with the servos and try flush the internal passageways in the case out. Most are simple straight drillings but there's a few complex ones, the throttle valve pressure to the pressure regulator is one.

I have a feeling there's an intermittent blockage somewhere. Or maybe a leak.

Phil

 

This evening has cooled off to 76°F.

Seems to be about the boundary temperature where the gearbox starts to work properly.
Drove it tonight and it behaved.

 

...56°F this morning and it's shifting perfectly.

Still need to pull the valve block off again and rod the passages but I think I'm at the point I want to just put a heavier oil in it.

Phil

 

Yup, it's that weather again.

Engine has too much torque for the belt to keep up with. Heh.

Phil

 

Today, went places.

One of the car's favorite places. They sell ethanol free gasoline so that goes in. Car runs noticably better on it.

Stopped at a little local place and picked up dinner. Real nice evening.

If I didn't have work in the morning I would have just continued to drive.

Phil

 

Day off today. Whim took me so I drove south to the end of the old road.

Desolate, with Mad Max vibes.

That used to be a busy little town, it's all but gone now.

Phil

 

Spent a good chunk of the weekend welding things together.

I really miss having a workbench, burned a few holes in my socks.

Phil

 

Just ordered a new belt at Napa, because this one does nothing but squeak and squeal any more.

Phil

 

Oil and grease tonight, needed it! Been piling on the miles lately.

Acting as taxi again. Went collect child #2 from her friend's house after her ride home didn't materialize.
Heater on, radio playing. Doesn't smell so heavy of burning oil any more. Valve guides are worn out.

Phil

 

Know what, somebody repaired my 60 mercurys c6 transmission.installed shi(f)t kit and now when its freezing itl spins rear wheel when shift to second
. I dont like it.when cold but good traction road surface its shifts much smoother than warm.
Something to think about..

 

Yeah, I think this would be a good use case for multigrade transmission oil...!

 

I drove to town today and braved traffic.

While doing so the gearbox did something it's never done before, hot. It shifted 4-3-2-1 coming up to a red light, then 1-2-3-4 correctly. Next stop it did 1-3 and got hung up not wanting to change to 4.

The drive home was pleasant, weather cooled off and the car was running like a dream. Smooth and quiet, effortless. It gave me time to think about what the gears did and I came to a conclusion, a theory (again) about what could cause such behavior.

At home, I reread the manual and then took the original valve block apart. Of interest, particularly, the throttle valve piston belonging to 1-2 shift shuttle.
I think it's a design kludge that was deemed good enough. The other two valves are identical, with a spring pushing against the force of the governor (speed proportional pressure) with a piston pushed by gas pedal position proportional pressure (throttle valve) to cause later upshifts the more the gas pedal is depressed.
The throttle valve pistons on those are free floating, pushed directly against the shuttles.
1-2 however was evidently a problem when the car sat in Drive, idle, that there would be leak down past the shuttle (only position with any pressure actively behind it at that point) and get in front of it and prevent it from moving correctly.
Thus, they created a drain in the top of the throttle valve hole by reaming it out and placing the governor spring between it and the shuttle, forcing it all the way in and opening the drain. When the throttle is depressed, the spring is overcome and the throttle valve piston shoots to the full extension position and makes contact with the shuttle.
However, the spring is supported only at each end. Cold, it appears to compress axially in a neat fashion. Hot, it appears to buckle into an arc. Normally that wouldn't be a problem because the drain valve would be brought into the hole in the casting by the throttle valve portion being machined accurately. Well, it's worn out and upon investigation and careful measurement it was possible to make it hang up halfway down it's travel by applying a gentle radial load to the end of the piston while pushing it into it's bore, the way the 1-2 shuttle would upon shifting from 1 to 2.


So, I committed an hydraulics sin. I machined a chamfer on the drain plug portion of the valve- much less critical than the smaller diameter section of the throttle valve end.
Now, applying a force causes it to self center and push fully home every time.
Measuring the depth at which it would jam solid against the position of the shuttle valve. It placed it in a halfway limbo- not far enough to change 1-2 but just far enough to leak off pressure in ways it's not meant to, causing havoc.

If circumstances allow, tomorrow I'll fit that piece and see if it makes any difference.

If it does, a thousandth of an inch mis-tolerance and an engineering oversight coming together cause a very undesirable mode of operation.

Phil

 

With all your knowledge of Hydromatics you may have a second job rebuilding them for Hamb members.

 

he should teach-the heck w/ doing the hands on-he is the guru by now!

 

It will be interesting to see if that works.

 

Swapped valve blocks. Now got the original one back in, with the modified piston.

So far, it works, driving down the street. Time will tell if that's good enough for being stuck in traffic.

Phil