Projects Mild custom '51 Pontiac Chieftain

TO-4 is suitable, from the spec sheet.
That's a double-no on F then; this gearbox has no qualm providing neck-jarring gear engagement.
It's just not meant to!

 

Let me know if there are any other parts that you would like to try from the hydro that I parted out. It’s still sitting, covered up on a workbench.

 

Cool that it's still straight 8. Be awesome with duel exhaust and multiple carbs. Don't ever put a regular v8 into it.

 

Bob,

I thank you for the offer. This valve block has been an invaluable tool in trying to get to the bottom of the trouble this gearbox has had. Right now, I think I'm okay. At least until the next round of experimentation and troubleshooting yields no results...

 

I was thinking about building an intake and exhaust for it. That may yet happen; I love the I8 and so long as it runs, it stays.

 

Oil change!

That's quite grubby. Winter always gets the oil dirty faster than in summertime.

 

Your shift problem; does it occur the same whether you drive it briskly and drive it in a leisurely manner?

 

If I accelerate hard it usually changes without quite so much violence; light throttle it's jarring.

Despite the main line pressure being good, I think where the oil sits in the valve block it overheats and thins out, meaning when the oil in the circuit is needed it leaks through instead of acting right.

It's 52°F this morning, I sat idling the car for 15 minutes waiting for the school bus to arrive, after which it changed gear going down the road perfectly; waited in line at McDonald's to get a coffee where it only changed up out of first when I lifted off.
Pulling out of the drive-thru and to the red light it changed jerkily to second. When the light changed it shifted like butter all the way up to 4th at about 40 mph on modestly heavy acceleration.
Usually it'll at least KA-chunk the drive line into third but today it merely shifted.

Thus, any leaks at the face of the valve block have been sealed, and it is able to work better.

So, I am gonna drop some heavier oil into it and see how that plays ball.

 

Phil, Id like to know which fluid you decide to use. Im putting a 50 pontiac straight8 hydramatic back on the road now. It Runs and shifts good so far. Ive put about 50 miles on it. Id like to change the fluid in the trans and have been unable to decide which fluid I wanna use. Ive thought about using the standard viscosity John Deere Hygard. Let me know what you decide.

 

Hy-Gard will not perform well, it's SAE 5 weight. That's too light for this transmission. DEXRON II is 15W and I'm having trouble when it gets warm.

I'll let you know what I get and the results.

Phil

 

Thinking of you with the weather. Hope you are ok

 

It was cool this morning; now 72 and climbing ahead of the weather headed in. Currently breezy but otherwise pleasant. That's likely to change around midnight.

I took the car out tonight. On the way home, with everything up to operating temperature I put my foot down coming off a red light. Normally there's a visible cloud of smoke behind, tonight no. Quite happy with that. Still need to do a valve job; haven't mustered the enthusiasm for that quite yet.

Phil

 

I was thinking maybe you should try adjusting the throttle pressure linkage a little one way or the other just a smidge and see if it improves or gets worse.

 

Well, the weather here was less bad than anticipated. This morning is now just chilly.

 

Been there, tried that. It makes no difference (apart from making hot operation much more violent).

 

Glad you dodged the "weather bullit". You don't need any more of that. Now if that Hydro would just behave ..... ! Anxious to see what heavier fluid does for you.

 

Hey Phil, I went and checked the viscosity chart for the regular hygard not the low-vis hygard and it shows it between iso 46 and iso 68. That puts it between 15 and 20w sae. Let me know your thoughts on that.

 

Still a little borderline for 90F weather.

 

I found one more to look into Phil!! Mobil Delvace tractor hydraulic fluid. The price is great.
Applications
Recommended by ExxonMobil for use in:

• Heavy-duty transmissions, differentials, final drives, hydraulic systems, power steering systems, wet brakes, PTOs and hydrostatic drives

• Off-highway industries including: agriculture, construction, and quarrying

• Top-up and refill of systems

• Commercial transmission applications requiring Type A (Suffix A), Dexron and Type F fluids. Do not use in passenger car automatic transmissions

• Applications requiring API GL-4 or SAE 80W grade lubricants in all gear applications except hypoid gear designs

• Outstanding replacement for engine oils recommended for hydraulic and transmission systems

 

It falls in the range of ISO 68 oil. Its shown as a replacement for type a and dexron and is heavy duty

 

Yeah, I had looked at that as an option. Certainly seems to fit the requirements on paper.

 

What if you disconnect the trans cooler/ heater from the radiator?

 

This transmission doesn't have a cooler, nor does it have provision to fit one.
Overall, it should be fine, in theory. Main line pressure never drops below 60psi (throttle closed) and about 80-85psi (throttle open) when hot; reverse boosts to 120psi as it should but it only behaves if the transmission is forced to cycle gears (and thus flush the fluid through the valve block regularly).
Where the oil sits static in the valve block and just heats up as it's doing nothing, that appears to be my problem.

Hence heavier weight oil may help.

Phil

 

So what is your theory as to why heat changes things now, when it didn't make a difference back in the day? What has changed or is warn or broken?

 

The early hydros don’t have external/remote cooling lines.

 

I have DEXRON II oil in it, which is "backwards compatible", but it's equivalent to SAE 10 weight oil; type A was 20 weight. So there's a difference to begin with. Type A is also quite a bit more gooey, which will block the leaks around the valves better.

So, a modern transmission oil, just too thin.

 

Is it possible to find the old oil on Ebay or at a swap meet?

 

A synthetic variant of Type A is available but the manufacturer states explicitly not to use it for an empty fill, just to top up existing Type A.

So, instead I'm going to use an agricultural/heavy machinery type hydraulic oil designed for wet clutch applications.

 

Oh, and also something I found recently adds credence - if I drive at a speed it sticks in 1st but should be in 2nd but not 3rd... After about 7-10 seconds it'll often change up into 2nd.

Basically once the oil has leaked past and is replaced by cooler, thicker oil it changes gear.

Tomorrow I'm going to buy a pail of 20W oil and see how that works.

 

One of the brushes in my heater fan motor disintegrated. That'll be why it wasn't running.

Ordered a new motor, this one's a bit past it.