MTF Comparisons?

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So been driving for 5 days with the valvoline synchro. The shifting is perfect. Not one crunch or hard to get into any gear. The downside is the trans is noisier and feels looser, probably because my 833 needs a rebuild. But it just shifts perfect after changing to synchromesh. I might drain a quart, and add a quart of 75w140 , to see if it will "tighten" up the trans without causing a shift problem. Trial and error, money, and time. Anybody have any experience with blending synchro with gear oil?
 
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So been driving for 5 days with the valvoline synchro. The shifting is perfect. Not one crunch or hard to get into any gear. The downside is the trans is noisier and feels looser, probably because my 833 needs a rebuild. But it just shifts perfect after changing to synchromesh. I might drain a quart, and add a quart of 75w140 , to see if it will "tighten" up the trans about without causing a shift problem. Trial and error, money, and time. Anybody have any experience with blending synchro with gear oil?
Can't wait to try it!
I just got mine today...

Screenshot_20240828_184854_Wyze.jpg
 
So been driving for 5 days with the valvoline synchro. The shifting is perfect. Not one crunch or hard to get into any gear. The downside is the trans is noisier and feels looser, probably because my 833 needs a rebuild. But it just shifts perfect after changing to synchromesh. I might drain a quart, and add a quart of 75w140 , to see if it will "tighten" up the trans about without causing a shift problem. Trial and error, money, and time. Anybody have any experience with blending synchro with gear oil?
If you try blending, I would use this, a straight 140 GL-4. Just an educated guess, but I think it's closer in composition than most other gear lubes. You might lose some of the shifting qualities you have with straight synchromesh, but it's a lot heavier than 75W-140. That'll give you a better chance of quieting down your trans.

CRC SL24228 Gear Oil + Cross Reference | FinditParts
 
If you try blending, I would use this, a straight 140 GL-4. Just an educated guess, but I think it's closer in composition than most other gear lubes. You might lose some of the shifting qualities you have with straight synchromesh, but it's a lot heavier than 75W-140. That'll give you a better chance of quieting down your trans.

CRC SL24228 Gear Oil + Cross Reference | FinditParts
I agree.
However, 75W-140 GL4 is the same as straight 140 GL4 when it's warmed up.
The viscosity changes as it's warmed up to full operating temperature.
The ''W'' in any oil is for winter, not weight.
And using GL4 oil is the right choice, not GL5 which is too slippery.
So, the oil flows like 75 weight oil when cold and changes to 140 when fully warmed up.
I think that this would be a better choice if it were me, but straight 140 would do the trick too, I'm splitting hairs here...
 
I agree.
However, 75W-140 GL4 is the same as straight 140 GL4 when it's warmed up.
The viscosity changes as it's warmed up to full operating temperature.
The ''W'' in any oil is for winter, not weight.
And using GL4 oil is the right choice, not GL5 which is too slippery.
So, the oil flows like 75 weight oil when cold and changes to 140 when fully warmed up.
I think that this would be a better choice if it were me, but straight 140 would do the trick too, I'm splitting hairs here...
I'm not a fan of mixing lubes to fix a problem. But if I'm going to try to quiet down an A-833 running Synchromesh by mixing something with it, I'm going to add a straight GL-4 140.
Because:
-You don't know how additive formulations not intended to be combined will react with one another. Very often their effectiveness is reduced. The 140 will have much less, if any viscosity index improver and/or pour point depressants than the 75W-140. Less addictive possibly means a smaller chance of poor additive compatibility. It's still oil, though, so at least the gears will be lubed.
- I don't know of the existence of a GL-4 75W-140. Lots of GL-5s, though. The small amount of EP sulfur/phosphorus additive probably wouldn't make much difference. But, see the previous point.
- Whereas adding a 75W to another 75W will probably do nothing in the attempt to quiet down the trans at cold temps, adding a straight 140 should work on both ends of the temperature scale.
- I think most if not all 75W-140s are synthetics. I don't have a problem with them, but some do. Gear clash due to synthetic is real. And does it play nice with mineral base gear lubes?

If this were my car, and if for whatever reason(s) pulling and fixing the trans isn't happening soon, I'd just run the 140. I ran that in a Super Bee year round in a state where it gets below 0°F in winter. It was hard to shift before warm up. The Mopar guy I bought it from said that was what was in it and I should leave it there. So I did. Not exactly buttery smooth shifting, but it got the job done.
 
I got 3 1/4 qts Out of the 833...
Only 2 1/2 qts back in before it started running out of the fill hole.
Should I Drive it around the block and then see if I can get more in there?
Service manual says it should take 4.
I would jack up the rear and run it for a minute and re-check. I wouldn't want to put a load on the trans knowing it's almost a quart down from where it was.
 
Service manual says it should take 4.
I would jack up the rear and run it for a minute and re-check. I wouldn't want to put a load on the trans knowing it's almost a quart down from where it was.
Thanks Man! Yeah, I jacked it up on one side and got the rest in there.
It runs thru the Gears just fine up on Jackstands.
Raining today... I'll take it out tomorrow. Fingers X'd.
 
I got 3 1/4 qts Out of the 833...
Only 2 1/2 qts back in before it started running out of the fill hole.
Should I Drive it around the block and then see if I can get more in there?
You should fill it until the oil comes out the fill hole while the car is level. I have a feeling you have more in there than you should.
 
You should fill it until the oil comes out the fill hole while the car is level. I have a feeling you have more in there than you should.
Lol, I took the Fill-Plug out Before I removed the Drain Plug.
Had to stick my finger down in there to feel the Fluid.
3 1/4 qts came out. So, 3 1/4 went back in. Even tho I had to force it.
 
Reheck level on flat after driving. Something don't sound right here.

The proper fill level is below the fill hole on a dry gearbox, rear axle, transfer case, etc. Fluid running out the fill hole is now overfilled.
 
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