What fluid for a 4-speed trans?

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I was always told in auto school.

Cast iron main case = 90 weight

Aluminum main case = ATF
 
Another vote for MT-90, while I haven't run it in an A-833 I did run it for years in the AX-15 5-speed in my Jeep and it made a big difference in shift feel and effort the first time I put that fluid in it (had 180k miles when I first got it and I put another 80k on it myself, never rebuilt). That trans has brass synchros like the A-833 and there aren't that many different ways to make a manual transmission. Newer ones just have internal rails for shifting and the synchros are made of different materials and may have multiple cones on the lower speeds (Tremec TKX, T-56 etc), that's about it.

I do remember it being a tad sluggish going into gear when it was really cold (below 15 degrees Fahrenheit or so) but after a few minutes driving was fine.
 
This helped with a shifting issue. Pennz Syncromesh

pennzoil.jpg
 
OK, my mind is blown! When I rebuilt my 833 about 10 years or so ago, I used 75-90 because I thought that was what we did. I have never heard of using motor oil (20-50) or ATF in an older 4 speed. I know that some modern manual transmissions use ATF, so I guess I can understand that. But is it really OK to use 20-50 motor oil???
 
harrisonm said:
OK, my mind is blown! When I rebuilt my 833 about 10 years or so ago, I used 75-90 because I thought that was what we did. I have never heard of using motor oil (20-50) or ATF in an older 4 speed. I know that some modern manual transmissions use ATF, so I guess I can understand that. But is it really OK to use 20-50 motor oil???
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Yes. There are probably several better lubes to use in MT applications, but 20W-50 or even better straight SAE 50 engine oil has been used for zillions of miles of service with zero of issues. A grade 50 motor oil has an equivalent viscosity to a SAE 90 gear lube. Probably just as important as viscosity is a manual transmission lube's compatibility with yellow metals. Hence, using a GL-4 or a modern MT lube is the best move today.
 
oldpunko77 said:
Question is how many bottles are need to be fill?
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Till it come out the filler hole. Sorrry, I don't remember. With my 833 I used to use half Redline and 1/2 Regular 75/90. Now just regular 75/90. No shifting issues. I once read synthetics aren't as good as you think in an 833 but you can't believe everything you read or I might sell you a bridge.
 
How long do you want your transmission to last? From rebuilding A833s, in standard and O/D, I run 90 wt gear oil. The high wear areas, are the spines on the synchro hubs, thrust washers, cluster gear mating surface, and the countershaft. Not counting synchro teeth jammed and clashing from power shifting. This wear is much worse on a trans that was run with ATF. With 90 gear oil the wear is almost nonexistant. Will an A833 last 100,000 miles using ATF? Yes, but I want it to last as long as possible.
 
Another vote for MT-90, expensive, but will make a noticeable difference in shift quality and performance over standard gear oil. I’ve tested this in 833’s and in my import cars with great results.
 
halfafish said:
I have an A833OD trans going back into my truck. I drained it a while ago and now I can't remember what it was filled with. The FSM says to use ATF, yet somehow I recall being told 80 weight gear oil was a better way to go? And of course on my truck parts shelf I have both ATF and gear oil standing by so there is no guidance to be had according to what's on hand.
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I'm not gonna read every post to see what all has already been mentioned....
For my personal testing:
>The best to use in terms of being able to shift fast is ATF (DextronII)
>The oil that will help your cluster pin to last the longest and the gears to not wear, is any EP oil, the thicker the Better.
But good luck trying to shift with 140 in it when it's 40 below; but you can use it in summer.
>However, the brass synchronizer rings in the A833 are not designed like in a Chevy or a Ford. They are not machined for oil drainage, so an A833 trans with EP oil in will take either more effort or take longer, to synchronize, or both. This goes double for the Super-Wide-Ratio A833ods.
You could try to use a multi viscosity like 85/115 in an attempt to cover both summer and winter, but again, it's still a slow-shifting E/P fluid. If yur not into winding yur engine up to redline and yanking on the stick with all yur might, what fluid you run as good as makes no difference.
Now having said all that, I used to run 100% ATF, summer or winter, and was very happy with the shifting characteristics. However, I noticed my cluster pin was wearing a little more rapidly than I wanted it to, and switched to 50/50, that is to say, half ATF and half 85W90 EP oil or MT90. That about stopped the pin-wear.
But the shifting was slowed down.


As to synthetics;
If you install a full synthetic,
Firstly it must be compatible for the manual trans, do not install any synthetic that has friction modifiers in it designed for a Limited Slip Differential.
Secondly, be prepared to flush it out, if you get gear clash (see note-1 below)

Note-1
One day I had the bright idea to see what happens to my shifting with a Full-synthetic. As I suspected it would; I got a lotta gear clash and really slow shifting at hi rpms.
So I took the trans down and apart. To cure the Gear clash, I cut the clutch teeth and sliders to make it a street "slick-shift." While it was apart I rearranged the brass, and deglazed the brake cones, then assembled it and roadtested it.
So ok that solved the shifting clash at highrpm. But it was still slow shifting. (with the synthetic)
So I took it down again, and hand-machined some drainage channels on the face of the cones, thinking that would get rid of the oil faster. Well, I couldn't notice it getting any better, so I drained it all and put the 50/50 back in that I had earlier drained out.
BadaBoom! now it was shifting pretty doggonenice.
So I took it down and apart one more time, and carefully washed all that full-synthetic out, one piece atta time . Then reassembled it, installed fresh 50/50, and that box now shifted so slick, it was unbelievable.
Around town, I can easily overpower the brass, and just slam it into the next gear. But granny shifting works too. And shifting at 7000/7200 is so sweet, and so fast, which for an A833 is almost unheard of.
The wear on the cluster-pin is as good as unchanging. and as for wear on the brass, well, I got 80,000miles or so on Second gear before it started complaining during granny-shifting.
There;
pick your poison.
 
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The close-ratio in my Valiant uses Penngrade GL-4 (formerly Brad Penn), partially because the spec sheets/web page specifically mention vintage musclecar 4-speeds. It's also about 1/3 the cost of RedLine MT90, which was my other choice. That car won't see cold-weather use, so no worries about the "paint stick in wet cement" sensation I had with 80W-90 in winter use.
I have a couple of bottles of Royal Purple's Synchromax fluid, which they recommend for any manual trans that calls for ATF. I shied away after I saw the GL-5 rating on it, though, only to find out later that RP doesn't use sulfur to achieve the GL-5 spec. Synchromax is safe for brass synchro rings. Since I already have it, I'll use that in the A833OD I built for my 170-cube '68 Valiant. The lighter oil not only shifts more smoothly, it's better for fuel economy.
 
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