48 Dodge D24 Fluid Drive Gears Grind

[bighammer48]

My '48 grinds going into every gear. The clutch is adjusted to the book, and the tranny linkage is adjusted by the book. I'm thinking maybe the tranny needs rebuilt, and / or a new clutch assembly is needed although the engagement of the clutch is positive with no slipping. What do you folks think?

[greg g]

Do you have any free play at the top of the clutch pedals travel.

[greg g]

The grinding indicates the schyncronizers aren't doing their jobs. They are located on 2nd and 3rd. they are basically there to assure the input shaft stops spinning when you disengage the clutch. If the clutch is not fully disengaging they can not over power the input shaft, which will continue to turn withthe clutch disc. I would suggest that you revisit your adjustment by lengthening the rod that conects to the clutch fork. You can remove the inspection cover and look to see when the adjustment gives you some space between the face of the throw out bearing and the fingers of the pressure plate.

If this doesn't work, and you have about an inch of freeplay at the top of the clutch pedal travel, then it likely a synchro problem.

[bighammer48]

Thanks to all who have responded. I will try to answer each question in order.

1. Yes. There is approximately 1 1/8" free play at the top of the clutch pedal;

2. The tranny has Kendall SAE 90 Transmission gear oil in it. The only thing I did to it was remove the floor pan during restoration. I still have the pan off, and wanted to address this before I put the interior back together. I bought the car with 22K verified miles on it, and it has been grinding since I first got it;

3. Since it may be a synchro problem, is this something I can repair myself? I am a retired body man and good with tools. I rebuilt the Mercomatic on a '54 Merc I restored several years ago, but have never opened up a stick.

Mike

[James_Douglas]

Hello (We tend to use real names here by the way),

First off, fluid drive refers to the fluid coupling which has nothing to do with the transmission. You can have Fluid drive with a M6 4 speed semi-automatic or you can have fluid drive with a 3-speed stick. Which one do you have ?

In either case, 80/90W is not what my books show as the recommended oil. It should be 10W engine oil. Also, never use 80/90W gear lubricant as the Hypoid additives (Extreme Pressure) will destroy any bronze parts over time and is not to be used.

Drain the thing and put in some 10W engine oil. One thing I would do is to drain the oil thats in it, full it with some 10W, manually put it in gear before starting it, jack the *** end up, then start it. Run it for 15 minutes, in 3rd gear to let the pump circulate the 10W. Shut it down, drain it while hot, refill it and then try it again.

The syncro's may have gotten stuck if it has such low mileage.

Best, James

[bighammer48]

James,

Thank you for the reply. I do understand the difference between the fluid coupling and tranny. I provided the info in the spirit of accuracy and completeness.

Anyhow, the 90W oil is what was in it when I bought the car, that is according to a lube sticker on the door post. I do have the owner's manual and I know about the 10W after reading your response. I didn't think about running it and doing the drain and refill which I will try this coming weekend.

To answer my other ?, should the tranny need synchronizers, is this something I could attempt? I know that there are tons of little needle bearings in some stck trannies that you have to make sure not to lose. Also, where would I buy the bronze sync rings? Bernbaum, or some where else?

Thanks for your interest and help,

Mike

[Young Ed]

Shel there are lots of manuals that run ATF per the factory. I wouldn't run the 10w for a long time but briefly I would think it ok.

[James_Douglas]

Hi Guys,

My mistake. When I saw the subject of "fluid drive gears" I assumed he had a Fluid Coupling and an M6 in the car.

A M6 uses 10W.

A 3-speed uses .....

Well that is an interesting question. I have a 2' think binder for the overhaul of my 3-speed and BW overdrive I put together over the course of a year. In it, it has the Chrysler, Desoto, and Plymouth 3-speed rebuilt pages from various years between 1946 and 1958.

Funny thing is that I found several DIFFERENT references as to what oil to put into a 3-speed.

The BW books say that the 3-speed with BW overdrive should use a 40W engine oil or a SAE transmission (gear) oil of 80W. It also warns against using a Hypoid lubricant in big bold letters. ATF should not be used for the same reasons.

My Desoto shop manual shows SAE 10W engine.

My Chrysler manual shows SAE 10W engine.

May Dodge manual shows 80W gear oil.

Now SAE gear oil is not the same thing as SAE crankcase (engine) oil. An 80W gear oil is about the same viscosity as a 28W engine oil. A 10W engine oil is about the same viscosity as a 74W gear oil.

Just remember that gear oil viscosity and engine oil viscosity are not the same thing. Unfortunately in our manuals they tended to use one scale or the other over the years and that can be confusing.

I run 30W engine oil in mine. I know people that use 10W engine oil in their three speeds for easier shifting.

I would run 10W in an old three speed for a few weeks to loosen things up then switch to 30W engine. The real reason I use 30W engine is that I can get one kind of oil for both the engine and transmission and I don't have to think about it.

Best, James

[bighammer48]

Hi Guys,

This may seem like a dumb question, but, with all of the references to engine oil being bandied about, are we talking detergent or non-detergent. I use detergent in my D24's engine because I put a modern spin-on oil filter adapter on it.

Also, No one addressed my question of whether or not I should attempt to replace the synchros myself, if necessary, or where I would even buy a set.

Thanks again,

Mike

[Jim Yergin]

Mike,

I rebuilt the transmission in my '41 Plymouth without any prior exeprience. It is pretty basic and if I can do it probably anyone can. To replace the synchros you wouldn't even have to deal with removing the countershaft or the input shaft just remove the output assembly.

I had good luck getting the parts I needed at these two sites:

http://www.dpmotorparts.com/

http://www.nwtparts.com/

The best investment I made was to buy a scissor transmission jack from Harbor Freight. Works like a charm.

Hope that helps.

Jim Yergin

[bighammer48]

Jim,

Thank you for the info. I have a transmission jack from my years as a body shop owner, but had some trepidation about opening up an old manual tranny. I feel more confident now.

Thanks,

Mike

[James_Douglas]

Mike,

Rebuilding the trans is no big deal. Just pay attention to the clearances in the shop manual. I would still try the thin oil first...if it has very low miles the syncro's just may be stuck.

James

[bighammer48]

Thank you again, James

[Don Coatney]

Shifting cars of this era requires a developed touchy feely method. Too quick and or too slow and it will grind every time. Once you find the sweet spot it should slip into gear without grinding every time.