would the syncromesh or syncromax fluids that came out in the 90's be better for the 833 o.d. than 80w-90 hypoid gear oil or ATF ?

I have used syncromesh with good results , I would never run ATF in any 833 I cared about .

[quote=Backfire]would the syncromesh or syncromax fluids that came out in the 90's be better for the 833 o.d. than 80w-90 hypoid gear oil or ATF ?[I've always used 80-90 but... somebody convince us./quote]

Mopar recommends ATF. I ran it in my 833OD and it was a good shifter, even in the winter.

If you do a search on here you will find a lot of threads on this subject and a lot of differing opinions. But there are a few things that the service manuals tell you. First, GL-5 is for differentials and is not the best choice for your tranny. Especially the GL-5 with Sure-Grip or Limited Slip additive. That was true 50 years ago and is still true today. Now that doesn't mean that putting Gl-5 in your tranny will smoke it, it just means that it is not formulated for it.

GL-4 is the lube designation you want for your tranny. And it can be difficult to find nowadays. And there are different weights of it, too. Correct me if I am wrong, but I think that our trannies want 80/90. The last time I had to find some, all I could find was 140. The tranny shifted real stiff with it, so I just kept cutting the gear oil with ATF until it shifted smooth, Ended up about 50/50 ATF and 140 GL-4.

I think if you look in the original service manuals, ATF was called for in colder climates. I personally do not like straight ATF for summer driving, but I am sure that someone will disagree. For me, a GL-4 with a viscosity that is not difficult to shift until it warms up is the way to go.

Pretty well thought out.

The GL-4 or GL-5 indicates the type of additive package in the oil.
GL-4 additive is anti-wear, sometimes there would be an AW in the nomenclature of the oil. It uses molecules that attach to the surfaces. In the beginning these Anti-Wear additives were made from tallow.

GL-5 was developed for the sliding friction that came into being with the invention of hypoid gears, sometime in the '30s, IIRC. These additives microscopically attack the surface of the gears and create an oxide layer. Under high loads, when the oil film is ruptured, the oxide layers on the gears prevent metal-to-metal contact and prevent the contact welding that would occur otherwise. The oxide layers are the last line of defense.

The chemically active additive packages work more aggressively on copper alloys, like the parts of the synchronizers made of brass or bronze. They also prevent the synchronizers from doing their job, which involves a certain amount of friction needed to match speeds between driving and driven parts. So use of the GL-5 oil can cause hard shifting.

There are several manufacturers of manual transmission lubricants that are GL-4. Redline's MTL is a prime example, but there are quite a few others. The problem of high viscosity on cold startup is solved by using a synthetic that has a much flatter viscosity vs. temperature curve. My friend who was an EMT in a high mountain town did that 30 years ago, although at that time there were only a handful of synthetic gearlubes generally used in the Arctic regions. But when he got a call when the temperature were 30 below, his 4wd was ready to go and there was actually lubricant flowing in the transmission and differentials.

One last thing.....Viscosity numbers assigned by the SAE are NOT the same for motor oils and gear oils. They were assigned different ranges of numbers to avoid confusion. So, 90 gear oil is about the same viscosity as 40 motor oil. If you already knew this, you're ahead of the game.

R.

Syncromesh says right on the bottle that it is for use in transmissions with BRASS rings ...

ATF just doesn't have the lubrication quality that a good quality gear lube has. Jamie Passon offers a good blend specifically made for Mopar manual transmissions.
Gus

I use Redline MTL
http://www.redlineoil.com/product.aspx?product=50204

But I'd also trust anything that Jamie had for sale or anything that Brewer's recommended. I just got hooked up with Redline years ago and haven't had any reason to switch away. My Doug Nash shifts better with MTL than anything else I've run in it.

Interesting thread.

Im just finishing a rebuilt 4 speed in my 65 Coronet.
I added a GL5 90 weight.
I have about 5 miles on Car.

Can I just drain and refill with 75/80 GL4?

Or is a cleaner needed?

Thanks

Transmission oil is like engine oil and most every thing else,"ours is better than theirs" depending or what you read/hear.Find out what the manufacturer recommends,they spent millions on R&D.

Sure can , there will be a small residual amount left inside and that shouldn't really matter. Let it drain overnight .

Last year I called valvoline on this question.
They stated that GL5 is not recommended for transmissions with yellow metal in them such as 833. They suggested GL4. GL5 will erode brass.

In 1973 the recommended Tranny oil ( per the service station manual and the auto parts supply store) for my 18 spline was 140wt..

That's what I refilled it with after installing a new front bearing cover..It was HORRIBLE shifting.....

I wouldn't think a cleaner is necessary. Just let it drain for a while. A little left over should not hurt

I also have had good luck with Redline MTL and Redline MT90 in several MT's though not 833's. Personally I would pick the MT90 for an 833 run in warmer weather. Should not do too bad in cold weather either.