Projects grandma's molasses versus spline rust

So I am in the parts collecting/prepping stage of a transmission swap project for a '56 Chevy.
The cast iron power glide does odd things at times, slipping, jerking, flare up between sluggish shifts and leaking. I rebuilt a fresh TH350 a couple winters ago prepping for the day when the powerglide finally gives out. My plan is to use the original driveshaft with a conversion u-joint and a yoke from a mid-70's malibu driveshaft that i have on hand.
Luckily, i tried to test fit the yoke in the transmission and discovered it won't slide in and out.
At some point, it sat outside and the splines are rusted. See attached photo.
My first plan was to sand blast it, but getting pelted with all the ricochet sand grains didn't seem very appealing.
Next plan was to soak it in PB blaster and clean it with a bottle brush. Soaked it for almost a year. Didn't help enough.
Thought about citric acid or vinegar, but am concerned it would eat away too much and leave a sloppy fit that causes a clunk.
After much searching on that hamb, that leads me to molasses. See 2nd photo.
So here goes.
My plan is to let it soak for a month and post the results. See 3rd photo.
Small jar of molasses was about $4 at local store. Used about 1/4 of jar to fill yoke.
There was talk of gingerbread men with the remainder.

 

I hope you are planning on checking it frequently; molasses is still an acid and can eat into some metals (particularly cast iron) over time.

 

Yeah I think the acids in molasses and citric are probably very similar. How strong you mix it will make all the difference.

 

PB blaster or WD with steel ,brass, SS
Tooth brush about 5-20 mints

 

Not sure molasses for humans will work. I have always used feed store molasses intended for cattle. It is much stronger and gets diluted with water. Does a great job. Friends have tried the stuff you have without success.

Dave

 

I would buy a container of EvapoRust find a plastic container the yoke fits is and cover it with the EvapoRust. EvapoRust will remove the rust in a couple days and is gentle on the steel. I use it all the time and it is reusable just pour it back in the jug or another container. It is not the cheapest option (citric acid, molasses, etc.) but does a really good job. See link here: https://www.evapo-rust.com/

 

I kinda remember my time using molasses ... it worked very well.
I just cant remember where I bought my gallon jug of molasses .... thinking it was a farmers feed store.
They mix it with grain when they feed horses I guess. Was pretty cheap buying it by the gallon though.
Seems like it was 1 gallon molasses mixed to 4 gallons of water .... or maybe more water, have to look it up.


This heater was in very poor condition, the doors were completely frozen shut, then the doors were so thin they would bend if trying to force open.
I let it soak for 2 weeks in a 25 gallon container out behind a shed in the deep part of the property .... it does smell.
The shell came out of the dip with shiny metal & the doors, defroster flap worked smoothly.

I remember reading it is not recommended and can be harmful to machined surfaces such as cylinder bores or bearing races .... sheet metal or body parts etc it works great.

 

You are right Dave. Cattle get beet molasses and humans get sugar cane molasses. Happy New Year, my friend.

 

Beet molasses works well !

 

Is there still a product called Rust Beeter? I saw it a few years ago. It's powered and you add water. The feed store molasses costs about a dollar a gallon.

 

I have used the feed store molasses a lot of times. I have an old rusty chain in a barrel of it now. It does work well if you give it time. But I soaked a set of cylinder heads in it for months and it put lots of tiny pits in the machined surfaces so you should pull it out often, wash it off, check it and resoak if needed.

 

I have used vinegar molasses and evaporust all work well. For sometime that small I would use evaporust it works faster. I don’t any of the products will eat the part, it should be steel not cast iron.

 

Just an aside, I remember a post years back showing a flathead block that got a molasses bath. Don’t remember the details as to how long, how diluted, etc, but the machined surfaces were pitted after the bath.

 

Feed store molasses for livestock is sulfated so it works better than store brand as I have been told. Have sheet metal in a tank now. Also works better when temperature is warmer.

 

For something that small just get a bottle of white vinegar, wherever it is cheapest.

Immerse it, and check it often, until the desired result is achieved.

 

Before you put it in a de-rusting bath, clean it well with carb cleaner (or equivalent) as most solutions won't clean oil off the part.

 

Citric acid and 3 days, that will look like new. I mix 1 lb to about 5 gallons of water, a quart would do for the yoke in question, mix accordingly. Hell, a quart of OG Pepsi would do the trick with more time.

 

For something like that (with a precision fit), I would splurge on Evaporust.

 

Yep, before and after on '64 Chevy bumper ends...soaked for a couple of days in Citric acid bath...

 

The yoke on my Olds wore out cuz of bad U joint and sloppy sleeve in tailshaft. I bought a new yoke for cheap on line. They are still available.

 

I filled a rusty gas tank with feed store molasses, set in on the garage floor for 3 days. Came back and the bottom of the tank was gone and molasses all over the garage floor. What a stinky mess to clean up.

 

>>>I bought a new yoke for cheap on line. They are still available. >>>

Well yeah. But what fun is that? When you can waste more time and maybe pay more for de-rusting concoction trying to salvage a rusted out part.

 

Thanks for the positive comments.
When i was posting this, i was thinking back to how tough the crowd was on this site years ago and wondered if molasses was just a hoax for new guys back then.
Update day 1: no noticeable difference in my sample area.

Follow up on comments:
The PB blaster soak and scraping with an old screwdriver got it to the point that i can tap it in place and tap it off.

I haven't been around feed molasses in many many years. My memory is that is really thick. Baking molasses is thin, almost like maple syrup.

After I paid a lot for a conversion u-joint, I discovered that modern spline yokes for the stock u-joint are available.

I plan to give this at least a week before doing something else. White vinegar or pepsi would be in line with the kitchen theme.

 

More than likely the rust was the only thing hold it together. I have had molasses leak from my wood and plastic “tank” sure left interesting patterns on the floor, now I do it outside.

 

I cleaned up some '35 Ford wheels with a long soak in horse molasses, it did a good job. Evaporust is great for smaller precision parts and tools.

 

A favorite story I read about molasses ..... Think it was here on the HAMB about 6 or 7 years ago .... could have been any auto forum though.

Three guys went in together and grabbed a free large hot tub that no longer worked.
They stashed it in a old barn and filled it with molasses. They were able to dip whole doors and fenders all summer long. ..... When they were through with it and dipped all they wanted, they dumped it out in the back pasture .... it works as a form of fertilizer also, so they got double use from it.

 

Citric acid works well, but I never use it for small parts.

 

I picked up powdered Molasses from Farm and Fleet. It works, but powdered citric acid from Amazon is less messy.

Both require a sturdy tub. The Walmart Christmas decorations storage tubs are too flimsy to move around when filling with the witch’s brew, and make a big mess when they crack.

Also, although I haven’t had a problem yet, I am afraid of the molasses attracting rodents if the tub is left uncovered. My mind is more at ease with the citric acid, although it’s a good ingredient also.

 

I have experience dipping stuff in feed molasses. Works well in warm weather but will take a couple weeks. I will not dip anything with machined surfaces due to the stories of etching of them.

 

The citric acid in the molasses is what removes the rust.

If the structural integrity of metal proves to be compromised after the process, it was already compromised by the rust and the citric acid simply removed the rust.