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This is one of those true stories that reminds you of the importance of the fundamentals: attention to detail, and conscientious workmanship.
Most of you know that I had my rear axle ratio changed from the stock 3.73 to 4.56, a couple of months ago, at a respected high performance shop. The shop came with great references, and the owner assured me that they had plenty of experience with rear axle ratio changes.
Stupidly, at exactly the same time as it turns out, Chevrolet got my new backordered driveshaft in, as I had been complaining about the “tinging” I was experiencing with the original driveshaft (a documented problem – see plenty of postings on this board about it).
I violated one of my long terms rules, because I REALLY wanted both changes made, about doing ONE change at a time.
Sure enough, after getting both changes made, I noticed that I had a new sound, that first became audible at around 35 mph (only if you have the stereo system “off”!) and does not sound anything like any sound I have heard before. I have described that sound in another posting on here (“Ping Jim G if . . .”), but to summarize, it is a “ringing” sound, like you would get by exciting a metal object made of very thin metal. My intuition tells me this is our famous aluminum, thin guage, large diameter “pipe organ” replacement “tingless” driveshaft vibrating at high frequency, but of course this is hard to prove.
When I mentioned it to one GM mechanic, he took a superficial look at that first replacement driveshaft, agreed that it seemed to have a fair bit of play at its yoke end (i.e. at the transmission tailshaft), but insisted it was acceptable, and that the sound was probably just a byproduct of the stiff rear axle ratio. I did not agree, and had the driveshaft both foam filled and rebalanced at my expense to quiet it down. That DID reduce the volume, but did not eliminate the sound. Since it was not irritating enough to make a fuss over, I didn’t worry about it.
A couple of thousand miles later, the SSR developed a transmission fluid tailshaft seal leak, and so I went in to a different Chevrolet dealership and they replaced the seal. A few DAYS later, the NEW seal started leaking AND I noticed I was now getting a perceptible shake in a narrow speed range centered on 65 mph. The Chevrolet mechanic agreed that there was a shake there, and that it had probably totaled the new seal, but couldn’t pin down its cause even after using a spectral vibration analyzer on the chassis. Both the original shop that did the rear end work, and my new tuner (MTI Racing), suggested that I tell the Chevrolet mechanic to check that driveshaft yoke AND the tailshaft bushing closely. He did, and 2 hours later Chevrolet had a new driveshaft, a new yoke, and a new seal on order for me. However, contrary to the advice of my 2 mechanics, they elected not to replace the tailshaft bushing, because “it looked and felt fine”. Reese at MTI shook his head when I told him, and said something like “Bronze is softer than steel Jim. If the yoke was found to be the incorrect as the mechanic told you, then it HAD to have battered that bushing up.”
Yeah, you guessed it. The shake is pretty much gone now, but the ringing noise is still there. I figure I need to wait for the next reoccurrence of either a seal leak or a shake, and then INSIST that this time Chevrolet replace ALL the pieces that interact with each other: seal, bushing, yoke, and driveshaft. And, maybe at the same time, fight the battle to get a STEEL driveshaft that won’t act like a musical amplifier for every driveline sound, as one other SSRfanatic member who WORKS at a Chevrolet dealer HAS gotten.
In the meantime, I also told Reese about the fact that Motive Gear, the supplier of the new rear axle ring and pinion, had called for a target 0.008” backlash clearance on the gears, and a minimum of 0.006”, but I wondered if that was too large a clearance to minimize gear whine noise. Now, Reese has done LOTS of ring and pinion changes – it’s one of his specialities at MTI Racing in fact. He has done lots of C5 and C6 Corvettes, both stick and automatic, changing the ratios to as high as 4.11 (which with the Corvette’s smaller diameter wheels yields pretty close to the same highway rpm as the SSR with 4.56 gearing). More dramatically, he used to be a crew chief for a race team (Mobile One), and once changed rear axle ratios on a fleet of race cars 87 times within 3 months! He KNOWS rear axles.
He always sets up ring and pinion backlash at around 0.005”. He says he does that because the clearance opens up a bit with normal break-in wear and because you need it that tight to get optimal engagement and low noise. He says there is no reason to have a loud rear axle, even with a 4.xx series gearset. After driving my SSR specifically listening to the sounds, he is as mystified as I am about the ringing sound, but said with confidence that he could get the gear whine reduced. Although the gear whine I had was nowhere near loud enough to be a factor for me, I asked him to take a look at my axle just to assure myself that everything was reasonably fine there, and so that when I have my future discussion with Chevrolet about the ringing sound, they don’t try to blame it on the rear end. Turns out that was a great idea.
After opening up, examining, measuring, and correcting and optimizing my SSR’s rear axle housing, Reese had lots of news for me.
- First, he noted that 2 of the housing inspection cover bolts had been stripped by his competitor’s mechanic, probably because that mechanic did not note that the SSR’s axle housing is ALUMINUM (like the driveshaft), and so had probably used an air wrench on the bolts, set to whatever he uses on STEEL housings. Reese repaired both of these, properly. By the way, they are METRIC.
- Secondly, he showed me with his dial indicator that the backlash, even though set and confirmed at the time at 0.008” by the competitor, was in fact now 0.012”. That would make it noisier.
- He checked the shimming, and found that it was close but not ideal, and speculated that that was because the SSR’s axle requires a different set of shims than Corvettes or Camaros, and that the competitor simply did not have the exact shims needed. Reese had his guy locate the correct shim set, and brought it in.
- He checked the spacers used elsewhere on the axle housing, and again, found that although close and acceptable, there was a special spacer set for our axle, and he procured and installed it.
- Then he checked the preload on the pinion bearings, and tightened it up, because with the aluminum housing, IF those bearings’ races ever got loose enough to rotate in the housing, they would go through that aluminum like butter, causing a quick failure.
- He checked the axle lubricant for any signs of metal, but found it was very clean, indicating that none of the deviations above had caused any undue wear.
- He had also checked the tooth engagement patterns, and was satisfied that they were acceptable.
- He refilled the housing with Mobil 1 synthetic axle lubricant.
The actual on-the-road results were interesting. The gear whine IS quieter, although I never found it objectionable at all before. To Reese, with his expertise and attention to detail, I’m sure that any excess at all would be an irritation. The ringing, just as I suspected, is still there and totally unaffected, proving that it has nothing whatsoever to do with the rear end, as we now have a rear axle that has been PERFECTLY set up by someone whose credentials would be VERY hard to dispute. So, when I next get either my seal leak or my shake, or both, I will say with great confidence to the Chevrolet folks “I want a completely new yoke, seal, bushing, and STEEL driveshaft”, since SOMETHING is making that ringing noise, and it’s NOT the rear axle. That new driveshaft assembly just isn’t quite right.
Reese says that a carbon fiber driveshaft wrap technology developed for race cars is now actually being commercially applied large scale to dump trucks. The reason is interesting. Apparently, some dump trucks that have 2-piece driveshaft (with a u-joint / bearing in the middle between the 2 driveshaft sections) experience failures in that center u-joint / bearing quite frequently, due to excessive driveshaft vibration. The carbon fiber is used as a dampening wrap to control the vibration. Reese says he could find out what the cost of that process would be for my driveshaft, but I am leaning towards leaving it bone stock until it causes another failure, so that GM doesn’t say the failure occurred because of “modifications to the driveshaft”.
But, getting back to the point at hand, MTI has effectively reminded me yet again that attention to detail and workmanship are incredibly important on a day to day basis. Extrapolate this thought. Attention to detail and workmanship in both design and installation are the difference between:
- SSR window seals that leak and window seals that don’t
- Auxiliary guage sets that work and those that get shorted and killed during installation
- Tonneau covers that seal and those that don’t (and so result in mildewing of the trunk carpeting)
- Roof hydraulic lines that don’t touch and scrape the roof, and those that do
- Driveshafts that don't ting or ring and those that do
- Etc., etc.
Makes you wonder how great our SSRs would be if GM actually HAD that attention to detail and workmanship. I’m not discouraged – I love my SSR regardless for all sorts of reasons. I’m just always looking for “great” rather than “ acceptable”.
And so evidently, is Reese at MTI. Gosh I am glad that Paul introduced us to each other. I wish there were more of us with similar values.
Jim G
Most of you know that I had my rear axle ratio changed from the stock 3.73 to 4.56, a couple of months ago, at a respected high performance shop. The shop came with great references, and the owner assured me that they had plenty of experience with rear axle ratio changes.
Stupidly, at exactly the same time as it turns out, Chevrolet got my new backordered driveshaft in, as I had been complaining about the “tinging” I was experiencing with the original driveshaft (a documented problem – see plenty of postings on this board about it).
I violated one of my long terms rules, because I REALLY wanted both changes made, about doing ONE change at a time.
Sure enough, after getting both changes made, I noticed that I had a new sound, that first became audible at around 35 mph (only if you have the stereo system “off”!) and does not sound anything like any sound I have heard before. I have described that sound in another posting on here (“Ping Jim G if . . .”), but to summarize, it is a “ringing” sound, like you would get by exciting a metal object made of very thin metal. My intuition tells me this is our famous aluminum, thin guage, large diameter “pipe organ” replacement “tingless” driveshaft vibrating at high frequency, but of course this is hard to prove.
When I mentioned it to one GM mechanic, he took a superficial look at that first replacement driveshaft, agreed that it seemed to have a fair bit of play at its yoke end (i.e. at the transmission tailshaft), but insisted it was acceptable, and that the sound was probably just a byproduct of the stiff rear axle ratio. I did not agree, and had the driveshaft both foam filled and rebalanced at my expense to quiet it down. That DID reduce the volume, but did not eliminate the sound. Since it was not irritating enough to make a fuss over, I didn’t worry about it.
A couple of thousand miles later, the SSR developed a transmission fluid tailshaft seal leak, and so I went in to a different Chevrolet dealership and they replaced the seal. A few DAYS later, the NEW seal started leaking AND I noticed I was now getting a perceptible shake in a narrow speed range centered on 65 mph. The Chevrolet mechanic agreed that there was a shake there, and that it had probably totaled the new seal, but couldn’t pin down its cause even after using a spectral vibration analyzer on the chassis. Both the original shop that did the rear end work, and my new tuner (MTI Racing), suggested that I tell the Chevrolet mechanic to check that driveshaft yoke AND the tailshaft bushing closely. He did, and 2 hours later Chevrolet had a new driveshaft, a new yoke, and a new seal on order for me. However, contrary to the advice of my 2 mechanics, they elected not to replace the tailshaft bushing, because “it looked and felt fine”. Reese at MTI shook his head when I told him, and said something like “Bronze is softer than steel Jim. If the yoke was found to be the incorrect as the mechanic told you, then it HAD to have battered that bushing up.”
Yeah, you guessed it. The shake is pretty much gone now, but the ringing noise is still there. I figure I need to wait for the next reoccurrence of either a seal leak or a shake, and then INSIST that this time Chevrolet replace ALL the pieces that interact with each other: seal, bushing, yoke, and driveshaft. And, maybe at the same time, fight the battle to get a STEEL driveshaft that won’t act like a musical amplifier for every driveline sound, as one other SSRfanatic member who WORKS at a Chevrolet dealer HAS gotten.
In the meantime, I also told Reese about the fact that Motive Gear, the supplier of the new rear axle ring and pinion, had called for a target 0.008” backlash clearance on the gears, and a minimum of 0.006”, but I wondered if that was too large a clearance to minimize gear whine noise. Now, Reese has done LOTS of ring and pinion changes – it’s one of his specialities at MTI Racing in fact. He has done lots of C5 and C6 Corvettes, both stick and automatic, changing the ratios to as high as 4.11 (which with the Corvette’s smaller diameter wheels yields pretty close to the same highway rpm as the SSR with 4.56 gearing). More dramatically, he used to be a crew chief for a race team (Mobile One), and once changed rear axle ratios on a fleet of race cars 87 times within 3 months! He KNOWS rear axles.
He always sets up ring and pinion backlash at around 0.005”. He says he does that because the clearance opens up a bit with normal break-in wear and because you need it that tight to get optimal engagement and low noise. He says there is no reason to have a loud rear axle, even with a 4.xx series gearset. After driving my SSR specifically listening to the sounds, he is as mystified as I am about the ringing sound, but said with confidence that he could get the gear whine reduced. Although the gear whine I had was nowhere near loud enough to be a factor for me, I asked him to take a look at my axle just to assure myself that everything was reasonably fine there, and so that when I have my future discussion with Chevrolet about the ringing sound, they don’t try to blame it on the rear end. Turns out that was a great idea.
After opening up, examining, measuring, and correcting and optimizing my SSR’s rear axle housing, Reese had lots of news for me.
- First, he noted that 2 of the housing inspection cover bolts had been stripped by his competitor’s mechanic, probably because that mechanic did not note that the SSR’s axle housing is ALUMINUM (like the driveshaft), and so had probably used an air wrench on the bolts, set to whatever he uses on STEEL housings. Reese repaired both of these, properly. By the way, they are METRIC.
- Secondly, he showed me with his dial indicator that the backlash, even though set and confirmed at the time at 0.008” by the competitor, was in fact now 0.012”. That would make it noisier.
- He checked the shimming, and found that it was close but not ideal, and speculated that that was because the SSR’s axle requires a different set of shims than Corvettes or Camaros, and that the competitor simply did not have the exact shims needed. Reese had his guy locate the correct shim set, and brought it in.
- He checked the spacers used elsewhere on the axle housing, and again, found that although close and acceptable, there was a special spacer set for our axle, and he procured and installed it.
- Then he checked the preload on the pinion bearings, and tightened it up, because with the aluminum housing, IF those bearings’ races ever got loose enough to rotate in the housing, they would go through that aluminum like butter, causing a quick failure.
- He checked the axle lubricant for any signs of metal, but found it was very clean, indicating that none of the deviations above had caused any undue wear.
- He had also checked the tooth engagement patterns, and was satisfied that they were acceptable.
- He refilled the housing with Mobil 1 synthetic axle lubricant.
The actual on-the-road results were interesting. The gear whine IS quieter, although I never found it objectionable at all before. To Reese, with his expertise and attention to detail, I’m sure that any excess at all would be an irritation. The ringing, just as I suspected, is still there and totally unaffected, proving that it has nothing whatsoever to do with the rear end, as we now have a rear axle that has been PERFECTLY set up by someone whose credentials would be VERY hard to dispute. So, when I next get either my seal leak or my shake, or both, I will say with great confidence to the Chevrolet folks “I want a completely new yoke, seal, bushing, and STEEL driveshaft”, since SOMETHING is making that ringing noise, and it’s NOT the rear axle. That new driveshaft assembly just isn’t quite right.
Reese says that a carbon fiber driveshaft wrap technology developed for race cars is now actually being commercially applied large scale to dump trucks. The reason is interesting. Apparently, some dump trucks that have 2-piece driveshaft (with a u-joint / bearing in the middle between the 2 driveshaft sections) experience failures in that center u-joint / bearing quite frequently, due to excessive driveshaft vibration. The carbon fiber is used as a dampening wrap to control the vibration. Reese says he could find out what the cost of that process would be for my driveshaft, but I am leaning towards leaving it bone stock until it causes another failure, so that GM doesn’t say the failure occurred because of “modifications to the driveshaft”.
But, getting back to the point at hand, MTI has effectively reminded me yet again that attention to detail and workmanship are incredibly important on a day to day basis. Extrapolate this thought. Attention to detail and workmanship in both design and installation are the difference between:
- SSR window seals that leak and window seals that don’t
- Auxiliary guage sets that work and those that get shorted and killed during installation
- Tonneau covers that seal and those that don’t (and so result in mildewing of the trunk carpeting)
- Roof hydraulic lines that don’t touch and scrape the roof, and those that do
- Driveshafts that don't ting or ring and those that do
- Etc., etc.
Makes you wonder how great our SSRs would be if GM actually HAD that attention to detail and workmanship. I’m not discouraged – I love my SSR regardless for all sorts of reasons. I’m just always looking for “great” rather than “ acceptable”.
And so evidently, is Reese at MTI. Gosh I am glad that Paul introduced us to each other. I wish there were more of us with similar values.
Jim G
