I have been driving various Mopar A833s, on and off,
for a total of over 32 years, since 1970, and
IDK what a third-gear crunch is, unless it is the sound that these boxes make when the synchro is not biting properly on the brake any more, and the slider starts crashing into the clutch-teeth, of whatever gear you are trying to engage.
What I have learned is this;
This condition is caused by a lack of synchronization, which means, the speed of the selected gear has not matched up to the speed of the driveshaft.
The reason for this could be, one or more of;
A) yur just jamming it too hard/too fast, and/or
B) the rpm has come down too fast, or is not coming down fast enough,
C) the struts are not working
D) the clutch is dragging, or
E) the oil is not dragging the cluster speed down in a timely manner, probably because of a misapplied viscosity, or
F) the oil level is just too high/too low.
G) the oil is sticking to the brake, preventing intimate contact, or
H) you're experimenting with the wrong oil; one that is too slippery, or that has bonded to the conical brakes or brass, at the atomic level,
If you can eliminate this sound with a different oil,
I think it only means one of three things;
1) the old oil you that were using wasn't working anymore and/or
2) the new oil is working correctly, or
3) the new oil is providing some kind of cushion that the slider has to deal with, BEFORE it can engage.
If it's #3, This takes time; if you don't need a fast shift, then that's fine, just wait for the slider.
Depending on which A833 you have, the Point of synchronization could be anything.
Suppose you have the standard box, with ratios of
2.66-1.92-1.40-1.00, the splits are .721-.729-.714
So in this case if you shift at exactly 5500 each time, the Rs will fall to
3966, and 4010, and 3927; so those are your synchronization rpms. The thing to note is that from 3927 to 4010, is a window of 83rpm, pretty easy to hit.
But suppose you have the overdrive model with ratios of
3.09-1.67-1.00-.73, firstly, you cannot jam into overdrive cuz you'll blow it up.
Splits are .540 and .599, so from 5500, the shift will come in at
2970 and 3295, a difference of 325rpm. This means, that you have TWO synchronization rpms to try and hit, and they are way way way down there, so, you're gonna have to wait for the rpm to come down, or it will clash; it can't help but clash, because the brass rings just do not have the power to stop all that spinning mass by themselves.
So guess what; A833 gears are not like Saginaws or Fords., they are stinking heavy. It takes time for them to slow down, and in the case of the overdrive, it takes nearly 50% more time to achieve synchronization on the one and 22% more time on the second shift, which in the regular box, are spread over three nearly equally spaced shifts.
So, for best results with either of these,
you are gonna have to run different viscosity oils in each, in an attempt to slow those heavy parts down, to some rpm that the brass can take over from..
And
that's just at 5500 ...........
Happy Shifting!
