These transmissions need to quit their whining

I don’t know how many times I’ve been driving down the road and a Honda Odyssey van or an Acura MDX will pass by and it sounds like it has a supercharger in it. Did this thing just get hopped up at the local speed shop? I think we can all agree that the answer is no. It’s the transmission, ready for a rebuild at the local transmission shop.

Here at H&A Transmissions in Rancho Cucamonga, Calif., Honda and Acura transmissions are our specialty. That’s all we do and we have plenty to say on the subject of whining. We field multiple calls for whining symptoms every day while taking in new orders for our remanufactured transmissions from independent repair shops, transmission specialty shops and dealers all over the country. There are many different combinations of whining symptoms that will point the finger right at the transmission. Some of the more common whining symptoms you might hear from a customer who brought a Honda or Acura vehicle into your shop are whining in 1st and 2nd gear, whining in park and neutral, whining at 40 mph and above or just simply whining all the time while driving. Generally the noise will be high pitched, from slight to downright loud. Honda and Acura automatic transmissions do not use planetary gear sets, they use single sets of input and output gears for 1^st through 5^th gear and reverse just like a manual transmission, which can make some big noise. So what is all this whining about?

This whining that you are hearing more than likely is gear noise caused by worn out bearing bores in the aluminum cases. The most common style of unit with noise issues is the 5-speed automatic three shaft unit that fits V-6 engine applications including the 2002-’06 Honda Odyssey, the 2003-’07 Honda Accord, the 2003-’05 Honda Pilot, the 2001-’02 Acura MDX, the 2000-’06 Acura TL and the 2001-’03 Acura CL. There are three pieces that make up a set of cases (or housings) for this three shaft unit. You have the main case, which is in the center of the trans; the bell case (or front case/bell housing), which sits at the front of the trans; and the end cap (or end cover), which sits at the rear of the trans (Figure 1). The bearing bores you find worn out are in the main case and the bell case and are what we will focus on.

The main case houses three large ball-type roller bearings that are the rear supports for the main shaft, the countershaft and the secondary shaft (Figure 2). These bearings take quite a beating from the constant load changing through the shafts via the clutch packs and gear sets as the vehicle makes its way down the road through daily stop and go traffic. The aluminum cases are just too soft and not strong enough to handle that thrust load over time and they begin to wear out. You will find the majority of the wear in the main shaft and in the countershaft bearing bores as they are your main input and output shafts and take most of the load. We currently do not see many issues with the secondary shaft bearing bore, but it is advised to be inspected along with the other bores.

The bell case houses the large countershaft non-ball type roller bearing, which is the front support for the countershaft and the other culprit for heavy bore wear. All of the output power flow is travelling through that countershaft to turn the ring gear and put power to the wheels to propel the weight of the vehicle. You will also find a smaller ball-type roller bearing, which is the front support for the secondary shaft. We do not see significant wear in this bore and find this to not be an issue but should always be checked as well (Figure 3).

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).

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

• Whining in 1^st and 2^nd gear can be caused by severe countershaft bore wear in the bell case. The 1^st and 2^nd 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 3^rd 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.