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These transmissions need to quit their whining

Thursday, July 31, 2014 - 07:00
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That being said, the perfectly round machined bores start to become egg shaped and the bearings start to move or as we call it “walk” in their bores and it can become quite severe. When the bearings are walking in their bores, the shafts walk with them. This in turn causes the gears on the shafts to mesh improperly and causes gear noise which usually sounds like a high pitched whine or howling noise depending on how bad the bore wear is. The improper meshing of the gear sets can cause mild to severe gear wear. You usually can see the uneven wear pattern on the upper or lower part of the gear teeth instead of the middle, where it naturally should be. One of the gears in the set will have pitting and/or metal transfer on the outside edge of the tooth usually towards the bottom, and its mate will have the same wear on the inside edge of the tooth. I like to call this “digging”. The gears are pitching which makes the outside corners of the gear teeth dig into the inside corners of their mating gears (Figure 4).

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We talked about different types whining symptoms earlier, and now let’s break it down a little bit further:

• Whining in 1st and 2nd gear can be caused by severe countershaft bore wear in the bell case. The 1st and 2nd output gears are on the countershaft and the first gear sits down at the bottom of the shaft just above the bearing bore and the countershaft gear itself. Usually this noise will go away when you hit 3rd gear.

• Whining in park and neutral usually is caused by countershaft and/or main shaft bore wear in the main case. This can cause the top gear set (or idler gear set) to sing us an unhappy tune. The engine load via the torque converter and the main shaft is travelling through the top gear set in park and neutral and this gear set sits just under the end cap and right on top of these case bearings. The countershaft gear in this set also happens to be the third gear with the third clutch pack sitting right on top of it, which adds extra weight and load at the top of the shaft. You can have top gear noise also while driving, but I would say park and neutral is the most common.

• Another symptom is whining 35 to 40 mph and above. This can be caused by heavy wear on the countershaft and ring-gear due to the countershaft bearing bores being severely worn, especially in the bell case.

• And last but not least, whining all the time while driving gets the least technical explanation being that more than likely all of the bearing bores are worn out and the shafts are walking all over the place so you may be hearing top gear noise, countershaft and ring gear noise and possibly all the gears in between.

So you have a Honda or Acura vehicle in your shop that came in for whining and you have the trans pulled and opened up on the bench and it’s time for inspection. Due to these bearing bores being egg shaped, it is possible to not notice the bore wear if the bores are not inspected properly. The most important thing to know going in is that the egg shape in each bearing bore wears at a specific angle due to the same repetitive thrust load over and over again. We have seen thousands upon thousands of worn Honda and Acura cases and these thrust angles of wear never change.

The easiest way to visualize it is by picturing the face of a clock. Each of the three bearing bores in the main case always have thrust angle wear between 2 o’clock and 8 o’clock and the countershaft bearing bore in the bell case always has thrust angle wear between 12 o’clock and 6 o’clock.  If you do not check the bearings at these particular angles, the non-egg shaped portion of the bore can be enough to support the bearing in the direction with the least wear and fool you into missing it. You will be on your way to properly inspecting a Honda or Acura case if you just follow a few simple steps of inspection procedures that we use here at H&A every day when remanufacturing our transmissions.

Let’s start with the main case:

• Set the case with the main gasket side down on the bench and the bearings facing up towards the ceiling.

• Make sure the case is turned so the bottom of the case is facing your belly. Stick the main shaft, the countershaft, and the secondary shaft into their corresponding bearing upside down until the shaft bottoms out and fits tight so you have leverage like a gear shift lever.

• Now move each shaft back and forth from the two o’clock position to the eight o’clock position. Put your finger between the outside edge of the bearing and the edge of the bearing bore to feel the true bore wear and to differentiate from the internal bearing clearance or “slop” (Figure 5).

Now the bell case:

• Set the case on the bench with the bell housing side down and the case turned so the bottom of the case is facing your belly.

• Stick the countershaft into its bearing right side up just like it sits normally in the trans.

• Now this time, move the shaft back and forth from the twelve o’clock position to the six o’clock position with your finger again resting on the outside edge of the bearing and the edge of the bearing bore to feel the movement of the bearing in the bore (Figure 6).

Have you found that your case bearings are walking due to some moderate to heavy bore wear? Well what do you do now? There are two choices available to you at this time. One is to spend an arm and a leg on a set of brand new cases from your local dealer, but I think most of us can agree that we are all fresh out of extra arms and legs. The other more practical choice would be is to buy a sleeved case.

At our sister company Gearspeed, we take a worn out case and have the bores CNC machined back to a true geometric center. The bore is now perfectly round again in an oversized state. We then bring the bore back to its original size by installing a machined high quality steel sleeve around the bearing. The bearing and sleeve is then re-installed back into the case and the case is ready to go (Figure 7). Now your bearings are properly centered again and are no longer walking and you can put your trans back together with confidence (Figure 8).

 So with the proper knowledge, inspection procedures, and parts, we can quiet down these whiners and get our customers down the road with a good quality product. We all love a good singer, but let’s leave that up to the radio and not the transmission. 

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