Technical 1950 hydramatic on the highway

Ive got to settle this for my own sanity. My 1950 cadillac with original 331 and single range hydramatic will be considerably wound out on the highway at 65 mph. So much so, that I dont take it on the highway because I feel like its working too hard for that.

I have some older guys I hang with who claim somethings wrong with it if thats the case, and that their 40's ford could do 90 with ease bone stock back in the day.

Im under the impression this is just how my caddy is geared and that highway speeds didnt have you going 65/70 back then (if the highway even existed in 1950!?)

They suggest its not going into high gear (which it is because I can count all 4 gears as it shifts), or that maybe the trans is slipping and needs a band adjustment?

Car drives fine around town, its just when I start to hit 50/55 I'm wishing it had another gear, and by 65 she's wound out too high for my liking.

I know a couple years after 1950, caddy had dual range hydramatics and much more hp, so thats apples to oranges there.

 

It could possibly have a damaged torus****embly, and therefore is "slipping", like a high stall torque converter would; those vanes are pretty thin material, and could be bent and torn up. If the torus cover has a drain, let it sit with the drain plug down, after driving it a while to get it warmed up. Then, drain the torus and see if there's any particulate matter that comes out; might even use a magnet to see if you can "fish" anything out. Bad thing is, if you do find a bunch of stuff, it's going to have to come out, and everything rebuilt; difficult finding anyone up to that task these days. There are a couple of specialty transmission rebuilders around the country, but they're not anywhere near cheap. Many years ago, I had several built Hydros, and lots of extra torus****emblies, torus covers, flywheels, etc, and some were damaged when I got them. The plan then was to use broken parts, with good parts, to make a useable torus****embly, since they are riveted onto the hubs. Got rid of everything before doing that however, and have regretted it ever since. I am Butch/56sedandelivery.

 

It doesnt seem to act like its slipping. Im just curious, is that behavior normal? To wind out around 65/70 mph?

 

Rear end ratio is either 4.27:1, 3.77:1 or 3.36:1 depending on model. Could it be running out of puff due to rear end or other things? http://www.classiccardatabase.com/postwar-models/Cadillac.php

 

Part of the problem is if you are used to driving a vehicle made after 1985 or so it has od and gearing that lets it go down the road at 2200 rpm or so at 60 mph. It makes the old car seem like it is turning too much.
Your 1950 car was built when about 3300 rpm at 60 was was the common. If you happen to have the 4.27:1 gearing, as stated above, that will be about where it will run.

 

According to that site - I have the 3.77 rear end. My model is the 1950 series 61 sedan.

That only shows the manual trans though. I dont know if a different rear was put in with the hydramatic

 

Find out what rear end you actually have... it could have been changed from the 3.77 over the years. Then get a tach and see what rpm you're actually running at 60 mph. Then you'll have a better idea of what's happening...

 

x2 on the tach-this will tell you if it is actually turning too fast on the highway. rear axle ratio,tire size will have an effect on engine speed too.

 

Agreed on first checking out what rear end you have. If you have the 4.27 to 1, you are going to be revving pretty high at 65.
If you have 3.77 or lower (numerically), then it should be able to do 90-100 pretty easily. That is unless the transmission isn't getting to 4th gear, which is 1:1.
Make sure it shifts 3 times in Dr. My 50 Olds 98 starts in 2nd gear, so it only shifts twice. (Still trying to figure out why, but there are others of same year that do the same too. I can do 65 with the engine just loafing along around 2500-3000 rpm.

 

If you're used to modern cars, the 3.77 ratio will make you think the engine is screaming at 65 mph. Heck, even the 3.36 ratio will make you think it's running a lot of RPM, compared to a modern car.

you could also install a tach (even temporarily), and see how fast the engine is running.

 

I believe your Cad should have a 3:36 ratio most of the other ratios are in stick transmissions or commercial chassis. My '49 with a 3:36 does seem a little low geared. Later models used a 3:07.

 

Well dang!

 

All drive trains except overdrives have a 1 to 1 top gear ratio, one fly wheel turn = one pinion turn at the rear end. Gearing determines how many pinion turns equal 1 tire revolution. You can approximate high way rpm by using one of the many on line calculators plugging in you tire diameter, rear end ratio, and speed. I run 28.75 inch diameter tires, a 4.11 rear and at 62 mph, the engine is at 3280 RPM. And it sure does sound a lot busier than the new Dodge Ram truck I drove the other day that was at 1750 rpm at 65 mph.

So either hook up a tach or do the math and get a reasonable idea of what your engine is actually turning at 60/65. If my Plymouth 6 can run down the road at 65 and have some reserve left, your Caddy should be equal to it also. I would be will ing you are beween 26oo to 2800 with your tire size and rear end starting with a 3.

Your engine's Peak HP was taken at 3800 RPM. If your are cruising less than 80% of that your are good to go. So you could be at 3040 all day, probably around 70.

 

If your Caddy still has ignition points, and you wish to hook up a tach, you might consider looking for an older style tach/dwell meter. Rig it up with some temporary extended wires so you can have it inside the car while test driving. The meter also would be useful for tune ups when setting the points gap.

You can probably find some used meters on eBay for not much money.

Ray

 

My 49 would go 80 no problem. You probably have a stick rear end.

 

With the online calculator I should be running 2500 rpm at 65 if I have a 3.36 and about 2800 rpm if I have a 3.77.

Im running coker L78 15's. (29.3 diameter).

Neither of those sound too high though. I do have a tach/dwell meter that I'll have to hook up and run inside with me.

The rear end is original along with everything else on the car to the best of my knowledge.

Thanks for the input guys

 

Had a 50 Caddy coupe Deville many years ago - did fine at highway speeds - which for me was 80.... What you are seeing is not normal....

 

Well my damn tach meter is for 12 volt so I wasnt getting anything accurate.

I took a video of me entering the highway and riding down to the next exit but by the time you do that all you hear is wind and the tires on the pavement.

Temp gauge started to creep up too..... Probably broke something free inside to clog up the rad! It has its off days. Old car for ya.

I checked the trans fluid though, pink as can be.

 

Route 66 was finished in 1926.


Cars were driving @ 65 and 70 before I was born. Your Caddy should handle that no problem. With enough room it should easily reach 95 or 100.

You need to know what your rear gear is a quick google search will tell you that the standard rear gear was a 3.26 with an optional 3.07.

I would guess that your transmission is probably slipping if you are turning mega revs at highway speed.

 

You are doing calculations for gear ratios/tire diameters....but you are not allowing the extra RPM due to normal slippage on any fluid coupling like Torus on an early Hydramatic, or convertor on a later A/T. Your figures are flawed, unless you had a lockup convertor...or a stick trans
.

 

So if its slipping do I need to tighten the bands?

Around town it feels fine. Doesnt feel like a lack of grab or anything

 

I should note (I forget at the moment what its called) but Im using the most current GM dexron trans fluid which I was told by a hydramatic expert that it was reverse compatible with the previous generation fluids. Basically the most current fluid is a thinner synthetic to get into tighter tolerances with higher sheer strength.

Im wondering if I use the oldest dexron you can currently buy if it would fix that slip.

 

Any fluid coupling has slip. It's not a solid connection. It's fluid being moved by an object, against another object, that causes the movement of the "driven" object.

Your hand swishing in a pond, shoving a wave at a floating beach ball. (Your hand is the engine and the ball is the input shaft of the trans) That fluid wave moves the ball, but not as solidly as a direct contact push. If you very slowly move your hand towards the ball, the ball won't move, but speed up your hand movement, and the fluid wave is strong enough to move it. That's exactly what a torus does to fluid, and why the fluid can move a car, and why it won't stall the motor when you get to a stop sign and let off the gas.

Changing viscosity won't eliminate the inherent slip in a fluid coupler.
.

 

Popular consensus would suggest that if it is slipping, it is in the area of the torus converter, which is a 'fluid coupling'.

Whoops! F&J beat me outa the gate...

 

Well, it' could be Systematic, Hydramatic, Ultramatic, Go Grease Lightin'

 

So IF it is in fact slipping, whats the course of action? A band adjustment or rebuild time?

 

If I recall correctly, the bands are only used in the lower gears....the clutches in both front and rear planetary gear sets are applied in high (4th) gear. If your trans is "slipping", then you probably have either a malfunctioning fluid coupling, as has been suggested, and/or slipping clutch pack(s).

In either case, the whole trans will need to come out. At that point it would seem an overhaul would be prudent. The key is, to first determine for sure IF you have any transmission problem at all.

Ray

 

Thanks.

There are some slipping tests in my shop manual that I can perform. I need to get my hands on a dwell/tach meter that works on 6v cars

 

The Trans is Junk Over haul it I drove these cars I know what I am Talking about. My cad could run 100 all day. Don in Indiana

 

Power your meter from a jumper pack. The pick ups should work as designed.