A833 Noise in Third

Hey everyone, another transmission question.

I bought a rebuilt a833. All the forward gears shift fine and go in without any issue, and the car drives fine. However, third gear makes a lot more noise than any of the other gears.

First and second are quiet, no noise at all.

Third makes a ton of noise.

Fourth makes almost no noise.

The noise in third and forth is only when I'm on the gas pedal, as soon as I lift off the gas or hit the clutch the noise goes away. Is this an issue within the transmission, or are they all like this? This is my first A833. I had an A230 and that didn't make any noise.

The transmission is filled with Redline's MT-90 synthetic. Below is a video of the noise I took last night. I know videos only do so much but this is the best I could do. The RPMS were close between third and forth, the downshifting didn't spike the RPMS.



Thanks,
Karl G

Pitted gears would be my guess.

Should not make any noise, except reverse. Probably improperly adjusted cluster gear clearance.

66fs said:

Should not make any noise, except reverse. Probably improperly adjusted cluster gear clearance.

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If this is the problem (I know nobody knows for sure until it's taken apart), would it damage the transmission if I drove it 3 or 4 hours on the highway this way?

I blew an A833 power shifting on by bracket car (4-speed small block with 10" slicks). You guessed it, ripped all the teeth from third gear. I have read elsewhere that third gear is the weakest link in this transmission (don't know why).

95dakotadude said:

If this is the problem (I know nobody knows for sure until it's taken apart), would it damage the transmission if I drove it 3 or 4 hours on the highway this way?

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I don't think so. Probably just needs a thicker thrust washer on the rear of the cluster gear. My best guess from the internet.

You sure that is not an overdrive box, where physically the third gear in the box is OD; but shifting wise, the third selected gear is Direct. Each gear should register successively lower rpm on the tach, at the same speed.

Running in Direct, which you say is not noisy, should be just fine, stay out of the noisy gear, until you have a chance to inspect it. My guess is the noise originates in the roller bearings in the back of the input gear, but I'm going more by logic than by anything else. In Direct gear, the input is locked to the mainshaft and power goes straight thru the gearbox. However,
ALL the OTHER gears are still spinning, just going for a free ride.

In Direct gear, the thrust is sortof removed from the cluster, and it is allowed to bang back and forth in the box. However this fore/aft motion is usually limited to a few thousands of an inch, and you never hear it . If you hear clunking, this is where it would most likely be coming from, unless the rear mount is busted..

The A230 and the A833 are very close cousins, and for the purpose of noise discussion can be considered the same.

If you did have an od-box, that od gear is very small, 18teeth IIRC, and has no torque carrying capacity. I have broken three of them, two with a 318. They will not take any shock-loading, and IMO, they should have a lock-out device on the shifter. So yes the od gear could be noisy.

And one more;
if the M/S bearing at the back, is worn out, then the MS can move fore and aft, carrying all 3 M/S gears with it. Since the forks are held stationary by the cover, so are the synchro sliders. I have seen the M/S gears get into physical contact with the cluster, and the front-most brass pop out of the slider because the struts came out too far. When this happens, the slider cannot return to neutral, and you will be stuck in direct gear. Do not rip on the stick, it will only make things worse.
Personally I would take it out and inspect it. You only need two specialized tools; a snap-ring plier, and a notched plate to press the back bearing off so you can remove the back two gears. But if the back bearing is tight and quiet, and the gears spin nice, and you are not having any grinding issues during shifting, then there is no need to take it apart. It's a piece of cake; any grease-monkey can rebuild that trans; I was just 17 when I did my first one.

I think your cluster gear, bearings, an/or counter shaft needs attn .
A general overhaul would be in order.
Yes, should be fine to drive, as 4th gear locks the input/output shafts together .
I would drive it, were it mine .
Good luck.

Since no gears really mesh once you’re in 4th it shouldn’t damage anything running down the highway IMO.

mcodecuda said:

no gears really mesh

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Not sure what you mean, as all the M/S gears in that box are continually meshed with the cluster. Every meshed gear has a clutch on it that the slider engages, at the command of the shifter, and then locks it to the mainshaft. I'm assuming you know that but just used the wrong phraseology