Super88chris

I have been test driving my olds and MOST of the trans does what it should except shift into 4th gear. Aside from pulling the trans out of the car what can I do to maybe fix this issue?

Vintage Chief

You aren't going to like reading this (below) thread (unfortunately). None-the-less, read it. You're most likely in for a significant amount of work (or, someone is if they want to work on it).

1955 slant pan Hydramatic, no fourth gear

Vintage Chief

The most likely candidate to resolve your issue is going to be a new transmission since it's likely the rear transmission band has broken. Simply pointing out the basic truth straight-away up front.

NOTE: In the URL link I sent to you what Glenn (redoldsman) states:

If you can find a 55 transmission fine, if you can find a 54 transmission even better.

Charlie Jones

Do you have a 1955 Oldsmobile shop manual?
1955 oldsmobile shop manual auto repair book | eBay
That will tell you all you need to know about testing and repairing this trans.
There are lots of tests and repairs that can be done to this trans without removing it from the car.
The first item to check is the adjustment of the linkage between the carb and the trans.
If this adjustment is way off, it could cause a loss of fourth gear,
Unless you know that the transmission fluid was changed recently.
Now would be a good time to remove the bottom pan and check to see if there is sludge or dirt in the pan.
You could also check the condition of the band mentioned in the thread posted above.

Vintage Chief

Charlie - Thanks for jumping in. Yes, Chris has the 1955 shop manual.

Super88chris

I have the manual book. It didnt say specifically how to adjust the throttle valve to get 4th gear. I know there’s something like removing the 3-4 servo and cleaning it maybe but I’m not diving into all that yet, easy fixes first. When this trans was given to me I had to add 8 quarts of fluid to get it up to the full mark. I will read more on the manual today. I put this trans in about two months ago. Also I’ve noticed when I check the fluid level when the car is running and warm, the fluid seems like it drips off the dipstick a lot as soon as I pull the stick out like it’s thin. And it seems if I look close enough it like there’s tiny little bubbles in the fluid. The book did say something about the fluid looking foamy. I won’t be replacing this transmission. If I can’t get it working then that’s the end of the line for me. I always already lucky enough to find one transmission that I got for free and I installed it myself at my old job but I no longer have access to a shop lift to do all that work again let alone find another hydramatic

Charlie Jones

Start with the simple things first Chris.
The throttle valve linkage adjustment is critical for proper operation.
There is a lever on the side of the trans connected to the throttle linkage.
Remove the clevis pin on that lever.
You will notice that you can move the lever back and forth against internal stops.
Hold the lever all the way back toward the rear of the car
Block the throttle completely wide open.
Adjust the linkage so the clevis pin slides in freely.

I suspect that in the process of installing a different trans this linkage may be improperly adjusted.

Super88chris

well I put the TV rod on the exact same way it was with the original trans but thanks for that info I’ll try that today. When you say hold the lever all the way back, do you mean after I remove the clevis pin, push the rod all the way downward so the lever in the trans is all the way back?

Super88chris

sorry if I need a little more explanation. A few days ago I had adjusted the tv rod a bit but not much. When I removed the clevis pin I could push the rod up and down to move that plunger inside the tranny in and out. Is that what you’re saying I should do?

Super88chris

So I looked in the shop manual and I saw a section that describes exactly what your talking about with the tv rod and I tried that and it seemed to get worse it would barely go into second and third gear and when it did it would slam in gear. So from there I slowly loosened the adjustment until gears 1,2,and 3 shifted smooth again but still not 4th gear, mind you I was only on my back road and I think the fastest I got was up to 45 tops. But I did manage to fix the kick down for going up hills, during all that adjusting.

Charlie Jones

Yes, then with the throttle wide open, adjust the linkage so that the clevis pin will fit in.

Wally

Chris, the manual explains how to adjust the rear band with the transmission in the car. It requires a special tool, I believe you can rent this tool from Fatsco Transmission. This would tell you whether you have a problem with the rear band. If the rear band is worn out or the friction material has come loose from the band you are in for a transmission tear down and repair.
Wally

Charlie Jones

Another thought;
A broken or mis-adjusted band could not cause a loss of fourth gear.
In fourth both clutches are applied, and the bands are released.

ub2693v

When my trans had no fourth it also had no second gear either, i did a test that is shown in the Hydramatic manual, get the car to approx 30mph, put into neutral and shut it off, turn the key to the "on" position and move the selector to drive, the engine should start back up from the pressure made by the rear pump that is powered by the movement of the driveshaft. My car did not start back up which tells me the pump was too weak to lock the clutches together, or the clutches themselves were shot but it didn't slip so probably a pressure issue.

Super88chris

Ok that’s all good info guys. I’ll try that driving at 30 mph and see what it does when I try to start it up again. Does it have to be 30 mph exactly. Could all this be because of bad fluid? Just weird that all 3 gears are good but I don’t get 4th. Like I said when I check the trans fluid with engine hot, it drips off the dip stick rather quickly, and it is a little above the full mark which is odd because I filled it up with the car running from having almost none at all on the stick. I think I had to add 6or 7 quarts. I did do the adjustment of tv rod. At one point i made it so it would barely go into 2nd or 3rd and when it did it was very harsh but now i got 2 and 3 shifting smooth.

Charlie Jones

Chris,
I think your next move, since you only added fluid, would be to drain it completely by removing the bottom pan.
There is a filter screen inside that should be cleaned.
Don't be surprised if it a sludgy mess.
Clean everything with solvent and a brush, as best you can.
The torus (torque converter) can be drained by two plugs near the ring gear.
Refill with Dexron III / Mercon.
A clogged screen can definitely cause pump problems.

Super88chris

ok. Sludge can it can cause it to not go into 4 gear only? And wouldn’t sludge show up on the dipstick? Yes I didn’t get around to trying the 30mph test today but I will tomorrow for sure and if still no luck I’ll drop the pan this weekend when I have more time. What kind of solvent? Is it really necessary to drain the torus? I can and will just checking

Charlie Jones

Sludge, and a clogged screen can cause a pump to starve for oil. Resulting in low pressures.
Spool valves depend on the proper pressure to shift.
Clutches depend on the proper pressure to lock up properly.
Draining the trans and cleaning the screen is periodic maintenance that should be performed every 30,000 miles.
You certainly won't waste any time by doing it. Since you don't know when (or even IF ever) it was done.
Stoddard solvent, mineral spirits, or even kerosene can be used to clean parts.
Yes. the torus should be drained as it contains half of the fluid.

Super88chris

sounds about right. I’ll get to it this weekend. I’m wondering if it’s not shifting because the fluid is too thin maybe it has moisture in it. Can I get those things at the auto parts store? And should I pull out that pressure valve while I’m at it, and the valve body and soak them?

Charlie Jones

Stoddard solvent is available from petroleum suppliers.
Mineral spirits are available at Lowes.
Unless there is an excessive amount of gum and sludge, I wouldn't mess with the valve body just yet.
The valve body is under the side cover anyway.
I would get a gasket for both.
FATSCO has them;
Fatsco Transmission Parts | United States, Worldwide Shipping

Super88chris

ok perfect thank you. I have my old trans at my house which I took off the side cover a few months ago so I’m familiar with it a bit. How should I drain the pan before removing? Do I loosen the dipstick tube? If so and I do that, does it need a gasket too?

Super88chris

I didn’t see the side pan gasket on that website but that’s ok. What does the rear band in the trans do? And is there a way I can check to see if it is ok? When I drop the pan.

Vintage Chief

Chris - The transmission you have in the car which was given to you - is it a 1955 transmission? I'm learning a lot following this thread, but I'd like to ensure I know what transmission y'all are working on. Thanks.

Super88chris

at my last mechanic job my boss had rebuilt a different guys 55 olds super 88 and converted it to a modern ls engine and whatever trans I’m not sure. But they pulled out the olds 324 engine and trans and that’s how I got this so one so yes I’m positive it’s a 55 hydramatic and I’ve been told 55 was the only year where they all had the same hydramatic transmission 4 speed

Vintage Chief

OK. Thanks, Chris.

Super88chris

also, I was told this trans was working when it was in that car, that was probably a few years ago then it sat but I’m not sure if it was working getting all gears. I am just about to go try the test of hitting it off at 30mph and see if it fires back up. So if it doesn’t come back on, that means the pumps aren’t working?

Super88chris

just tried that test at 30mph and the car started back up!

Charlie Jones

There may be no drain plug on that model.
If so, remove the pan by starting in one rear corner, and removing bolts one side then the other until you reach the opposite corner. loosen the last bolt and pull the opposite corner away.
Make sure you have a big pan under it.
Don't bother the dipstick tube.


The rear band locks up the ring gear of the rear planetary gearset.
This puts the gearset in reduction.
You may be able to see the bands with the pan off.
If your trans works in gears 1 thru 3 your problem isn't bands.

I think you will be able to tell a lot more about this trans once you get the pan off.
Read that whole trans section in that shop manual. A lot of good info there.

Super88chris

ok got it. I don’t have a lift so I’ll have to do all this while the car is on jack stands so it’s gonna suck I’m sure. That’s good news it isn’t the bands then. Let’s just hope it’s not something worse, I’m really hoping it’s just sludge and I can clean it out

justacog

If the 55 is similar to the 54 hydramatic (excluding things like tailshafts, bell housings etc), you drain the transmission by removing the dipstick tube. It's a lot cleaner way to drain the fluid as well as re-use the fluid if the fluid is fairly new. You've got to do that anyway to remove the bottom pan and/or the entire transmission. The dipstick tube seals itself with an "AN" metal to metal connection. The "flair" on my dipstick tube had a slight ding in it that prevented a complete seal so I found the right size o-ring that could sit at the base of the flair inside the pan so solve that issue.

The side pan usually will need a seal kit for the shaft coming out the side. The is one seal that gets press up against the side of the pan with two "dished" washers. It's REALLY important to get those washers back in, in the right order and orientation to seal up where that shaft comes out the side of the pan. There is also a really tiny o-ring that goes behind a small washer, held in by a pin. It's really hard to see, but it's there. That o-ring seals between the concentric shift selection shaft and the throttle position shaft. Obviously, putting on fresh bottom and side pan gaskets is highly recommended, if those gaskets are old. If they're fairly new, they can be re-used.

Charlie Jones

All good advice justacog.
I forgot that slant pans drained that way, through the fill tube, Slim jim's drain that way too.

Super88chris

ok I will be reading this post again when I take off the pan this weekend. Ok so if I’m getting 1-3 gears then is my valve body ok? Cuz I really don’t want to mess with all those o rings and side pan stuff if I don’t need to clean that valve body.

Wally

Chris,
When you get brave enough to tackle tearing down the valve, I would suggest you invest in an Ultra Sonic Cleaner. You can get a small one at Harbor Freight for about $90. It's the only way to go when you want to get small parts clean. All you need is warm water and a shot glass of Simple Green. The parts will come out looking like new. Just make sure you take lots of pictures as you take the valve apart. The diagrams in the manual are very detailed but you need to make sure you identify each spring and each valve spool as you take the valve apart.
I've done a couple valves so if you need help just let me know.
Wally

justacog

I recommend caution with Simple Green in an Ultrasonic. Regular Simple Green will etch aluminum if the part is left in the ultrasonic too long (It will start removing the anodizing first on a carburetor in a very short cycle). They do sell an "Aviation Simple Green" that doesn't have this effect. I've heard that Dawn dishwashing soap works just as well in the ultrasonic without the potential damage to aluminum and other soft metals, but I haven't tried that yet. One other tip is that if you buy a big ultrasonic cleaner (nice for doing carb bodies), you can ziplock baggie a bunch of smaller parts, when doing a small job, that's filled with your cleaning solution, fill the ultrasonic with just water and put the baggie with parts and cleaner into that. Saves you from wasting a lot of unneeded cleaner.

Also, it's highly recommended to use distilled water with your cleaner, not tap water. Something to do with "streaking" the finish of your parts.

Super88chris

right on thanks guys I’ve seen those ultrasonic cleaners and can’t afford that right now. But I really don’t wanna get into the valve body unless it’s the cause for not getting 4th gear?

ub2693v

The valve body can easily be cleaned with gasoline, cheap and very effective (although explosive/flammable so be careful) Have the shop manual handy when it comes to reassembly, there is only one check ball involved, its nowhere near as complicated as todays valve bodies but quite a feat of engineering when it first came out. The second transmission i used had some varnish/sludge in the valve body, i used coffee filters to wipe things down after soaking in gasoline overnight. I would definitely do this as a last resort though. A simple test would be to disconnect the TV rod from the transmission itself and manually move it in the direction the throttle actuator would, you should feel spring tension the entire time, if not then you'd know the plunger is stuck and that it will for sure require disassembly. As for the gasoline cleaning, do so at your own risk, i use it from time to time because it is an excellent solvent but it is also extremely dangerous and things can get ugly in a hurry!!

Super88chris

oh yeah I’ve heard this before, I thought you soaked it without disassembling it tho. I’ve already done that and can tell you there is a little bit of play before I feel spring tension

Super88chris

when adding new trans fluid is it ok to get the stuff from Walmart if it says compatible with Dexron 3 or mercon?

justacog

No. The most probable cause is the valve body. If you look at your service manual (I think you bought one), there is a diagnosis section towards the end of the Hydra-Matic section. I have the 1954 version and its on page 12-104 for me:

Nature: "Transmission shifts satisfactorily through 2nd and 3rd speeds (Dr range), but will not shift into 4th speed (Dr range)."
Cause: " Sticking 3-4 shifter valve and/or governor valves."
Correction: "Completely disassemble and inspect valve body and governor assemblies".

The valve body needs to be disassembled, not just "soaked".

Vintage Chief

Owning the manual isn't good enough? You actually have to read the damn thing?