Technical 49 Hydramatic frustrations

Firstly Seasons Greetings from over here in the UK.
Can anyone give a bit of Hydramatic advice please?
Its in a 49 Rocket 88. Forward Drive works but Reverse gives a horrible grinding noise when trying to engage.
Ive had the engine and box out. Pulled the Hydramatic oil pan off and partially stripped it down to clean and reseal . All appeared ok inside.
Tried to externally set up the bands yesterday with it running but without much success using a box spanner and a socket.
The manual talks of several special tools. Some look like spacer Shims to preset the adjustment of the bands with the sump off.
Anyone made up a similar tool to do this?
Id appreciate any advice, many thanks, Jim

 

Maybe @PhilA will see this and chime in. There are others that certainly know their way around the hydromatic that might jump in here also.

 

Reverse pawl is what's making the horrible noise. Don't let it do that, doesn't do the mechanism any good.

First, a question. With the engine off, engage R. Does the car correctly lock the transmission up in park?

Phil

 

(Jim, I missed the questions you had posted about adjustment and tools before, but I can lend my experiences).

First epicycle needs a tool making up- real simple. I used a brass pipe fitting and a bolt. The actuator piston housing has a small blanking plug in the bottom, threaded into a tapered thread so it binds up and seals.
I took a fine threaded bolt and cut a thread for it through the middle of a brass pipe fitting (easy to work with, cheap from hardware store), so the pipe fitting screwed into the tapered thread and stuck there, providing a through thread for the bolt. I domed and polished the end of the bolt because it acts directly on the piston and I didn't want to be grinding swarf off. Dialed it by hand until it touched, then having worked out how many turns I needed from the TPI of the bolt, dialed in the preset. I then set the band tension with the bolt and locknut on top.

Second epicycle can be set with a measuring stick (I used a plastic vernier caliper, one with a dial I use for woodwork) and careful distance adjustment from the datum of the bottom of the piston barrel.

I don't have my book with me right now but if you need the measurements, let me know.

Phil

 

Second epicycle measurement. 5 7/8" from the base of the housing. Wind the thing in and lock it off at that measurement. That's the easy one.


This is the plug in the base of the first epicycle piston.

Brass pipe fitting. Threaded.

Bolt, domed and polished.

Allows the bolt to pass through unhindered.

Tightened down. Calculate turns for 0.3" preload, then tighten up band until it grabs just enough you cannot turn the epicyclic drum. Remove bolt/fitting and replace plug.

That's the band adjustment, which you'll need to do if you've been adjusting the tensioners.

The shims are for endfloat on the mainshaft- that's a pain but it needs to be correct. Let me know if you need that method also.

Phil

 

thanks for the help, much appreciated. I will digest it and get back on here when time allows. Cheers, Jim

 

No worries. The easy question stands; does the transmission lock up into Park if you switch off the engine and select Reverse?

 

1950 and before had a manual locking reverse carrier. This caused noise when shifting into reverse. Try going to Lo and wait a second, then shift to reverse..

 

Yup. If all it does is grinds then it's not engaging correctly is my logic- without pulling it apart to see if the pawl is broken, engine off/Reverse should manually allow the pawl to correctly engage if it's going to.

If it doesn't, side pan off and inspect.

 

Nifty solution to the front band adjuster. Does the later model Dual Range Hydramatic use the same 0.3" dimension?

 

I believe so; the only major revision was the valve assembly for the Dual Range.

I would have to go look in my book for the actual fraction of an inch- I had commented 0.3" in my notes when I rebuilt mine.

Phil

 

Thanx. I think thats the case too. All the parts look identrical. I set my bands 20 years ago using the X- number of turns on the external screws method and it has been a really smooth and responsive operator ever since.

 

Thanks for the info.
Yes, the Trans does lock in R when not running.
I have set up the bands as per your helpful instructions and refitted the oil pan to run it. I connected an oil pressure gauge
Oil pressure to the box is initially 80 psi on start up,this then drops rapidly to around 20 psi.
My reprint shop manual says 55 to 80 when hot at 375 rpm , guessing this can be in N or D.
(My idle speed wont go much below 600-it has an edelbrock carb and is a 303 bored to 324 with 56 code 10 heads and rockers.)
It still graunches into reverse when running. Low pressure may cause this?
The car is not driveable at the moment as it is stripped out for welding. I need to be able to move it under its own steam.
Is there an oil pressure valve in these boxes?
As always, I do appreciate any help.
Jim

 

Very much so. It should hold 60 psi in all gear positions apart from R where you should see it wobble between 140-160.

That's definitely a problem- jack the rear wheels up on stands and put it in Dr, and get the speed up to about 25-30 mph and see if you get oil pressure back up.

Phil

 

Ok, started it up today. Pressure at 80, dropped steadily to around 20 in N.
Put in Drive and revved to approx 30mpph. No change in pressure and a pronounced dry humming noise from the transmission.
Which isnt good.
Some background. The car has always leaked ATF from the bellhousing.Reverse often used to grind when engaging. Shift between 1 and 2 was very firm and "sticky"-it would delay then go in with a wallop. sometimes it would lose fourth gear. No other undue noises.
I removed engine and box as engine needed work too. Partially stripped box to mainly reseal the leaks. There was some swarf on the strainer(reverse?).
I'm not experienced with the insides of automatic transmissions but have worked on more modern Volvos etc for decades so feel i have a reasonable level of competence.
My impression of the problem is a pressure control one. The oil pressure starts fine then drops. This suggests to me the front pump is working as a pump. As for the rear pump, surely that should add pressure as roadspeed increases?
My main problem is that im over in the UK and 70 year old Hydramatics are not common here!
I do have a 56 one that came with a scrap engine but the oil pan looks different and tailshaft is different length.
It looks like box out time again i fear, Any ideas?
Thanks, Jim

 

Yeah, reason I said to run it no load was to see if the pressure was being bled off via the one way ball valve that the rear pump adds to the system with.

If it's making unhappy noises and you found swarf up in there .. that's important info.

You had the rear annular out- was that all you pulled out, or did you pull the drums too? They hide a lot of trash inside if a bearing's failed and ideally need to be cleaned out. Good time to inspect the clutches too- if it's become hot enough to trash a bearing then the cork friction material on them may be quite degraded.

The fact it's leaking down is a concern, particularly in N. There's a couple of major places it can lose fluid pressure. Normal operation the regulator shuttle, primary pump pressure relief (former screws in externally to the pump housing, latter is integral to the front pump), one of the control valve shuttles could be stuck in exhaust or something's broken, or as you posit, you have a majorly failed seal somewhere.
It not changing gear well and a harsh 1-2 thump is a sign of low oil pressure at the valve block. That and the 1-2 control valve piston may be sticky (it sees the most use and wears accordingly), but losing 4th suggests failed seals in the clutch drum annulars as it needs the most fluid to hold both in for direct drive.

Yeah, the 56 version was an almost complete redesign.

How far did you tear it down before?