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Some of you know that I have been contemplating a change in rear axle ratio on my 04 SSR to improve nimbleness.
I may also have mentioned to a couple of you that I run a small Internet business in which I use custom performance modeling computer software to determine for my clients what re-gearing they might do, to their cars or motorcycles, to optimize the performance for THEIR target use. Naturally, I applied the normal modeling process I use for my clients to my own motorcycles, and now to the SSR.
As it turns out, the modeling software predicts pretty impressive results in the case of the SSR.
To review a bit first, the stock 3.73 axle ratio in the SSR sounds impressive, but only until you remember that this is a 4800 lb vehicle BEFORE you add fuel, driver, passenger, and other load. In addition, the SSR, like all other vehicles made to sell in the United States, is geared from the factory to try to optimize fuel mileage for a better corporate average, rather than to optimize performance. Finally, we all have different target uses and preferences for our vehicles, and I suspect that maximized fuel mileage is not high on the priority list for the typical SSR owner, if it interferes with throttle response performance.
My own preferences and target objectives are a little sporty but pretty sensible overall:
1. I never cruise, for more than a few minutes, at speeds above 78 mph (I try to stay under 5 mph over the posted limit, which on the fastest freeways is 75 mph, to make myself an unworthwhile target for a police officer to paint with radar)
2. I DO like the periodic blast up to 100 mph or so, but only on deserted country roads where “there is no one in the forest to see or hear the tree fall”.
3. I do like carving along windy, hilly, narrow country roads at speeds that are “brisk” but not anywhere near pushing any boundaries
4. I don’t ever “race”, or really “speed”, on the street or anywhere else. I value my skin and bones, my low insurance premium, and the safety of my fellow drivers too much
5. I like satisfying throttle response in the 0 to 90 mph range, WITHOUT needing to force the automatic to downshift to get it
6. I normally like lightweight vehicles, so the heavy SSR is an exception for me (I fell for the retro styling and the untypical boldness for GM!!), and the deadened throttle response caused by the weight warrants addressing
7. I LIKE the sound of a higher revving engine – it makes any vehicle more exciting, and in the case of the SSR, that sound is pretty nice – like the sound of a Ducati motorcycle engine is!
I used these criteria to do some iterative performance modeling in my software, assuming MY weight and 13 gallons of gas, and learned a few things. I have found in the past that the quick shorthand way of best expressing what I learned, without the normal 9 to 15 page modeling results report, is by giving you some 0 to 60, 0 to 100, and ¼ mile times.
My stock SSR with the 300 hp GROSS / 250 (dynoed) hp NET hp 5.3 liter and stock 3.73 ratio, 160 lb driver, and 2 gallons of fuel:
0 to 60 mph:7.61 sec
¼ mile:15.84 sec at 90 to 91 mph.
0 to 100 mph: 19.39 sec
With ME and 13 gallons of fuel aboard (a more reasonable approximation of my SSR’s actual loading, those numbers become:
0 to 60: 7.86 seconds
¼ mile: 16.04
0 to 100: 20.10
Changing from the 3,73 to a 4.11 axle ratio, but keeping everything else the same:
0 to 60: 7.43 (0.43 sec better)
¼ mile: 15.76 (0.28 sec better)
0 to 100: 19.38 (0.72 sec better)
Changing from the 4.11 to a 4.56 axle ratio, but keeping everything else the same:
0 to 60: 7.03 (0.83 sec better than stock 3.73)
¼ mile: 15.54 (0.50 sec better than stock 3.73)
0 to 100: 18.60 (1.50 sec better than stock 3.73)
Then, I looked closely at the stock internal ratios of our 460 automatic (this is for 03 and 04 SSRs, remember – the 05 auto transmission is different I believe). The internal ratios are NOT designed for performance, but rather for flexibility and the EPA mileage test. There is a HUGE drop in rpm between gears, and a particularly disastrous one on the 1st to 2nd shift, that drops the rpm from redline down to only 3200 rpm. You can imagine how low the power output is at that rpm!
So, I tried upping the rev limit from the stock 5900 to 6200. That knocked 0.15 seconds off the 0 to 60 time, regardless of which gearing I modeled. With the 4,56 gearing, that dropped the 0 to 60, even with my portly body and 13 gallons of fuel, down to 6.9 seconds (a lighter driver with 2 gallons of fuel aboard would be appreciably quicker).
So, to summarize, if I go to 4.56 gearing, and also raise the rev limit (via LS Edit at the local tuning shop), I get the following improvements:
0 to 60: -0.96 sec
¼ mile: -0.65 sec
0 to 100: -1.65 sec
That’s a HUGE improvement.
The gear swap will be done at a well respected speed shop (Lamar Walden Automotive in Atlanta, where I am apparently going to stay on a temporary contract assignment for a year or so!). That shop has done lots of rear end changes and knows the subtleties of setting the clearances RIGHT (don’ t try this at home as an amateur). Done by these pros, it will cost $850.
Now, let me ask you, where else can you get -0.96 sec in 0 to 60 time, -0.65 sec in ¼ mile time, and -1.65 sec in 0 to 100 time for only $850 parts and labor TOTAL? THIS is the performance mod bargain in the array of choices.
Yes, the rpm at highway speeds does increae by 22%. That still only means:
2198 rpm at 60 mph
2564 rpm at 70 mph
2858 at 78 mph (my absolute highest cruise speed for more than minutes at a time)
These are acceptable. Check out the rpm at 60 mph for other performance oriented cars. This is higher than many, but not as high as some with engines of comparable capability and features.
Don’t sweat the fuel mileage either. If you haven’t yet read my earlier posting on fuel mileage on this board, you might want to check it out (“Incredible but true – gas mileage vs gear ratio test”).
I think this might be THE killer “bang for the buck” mod for 03 and 04 SSRs.
Or, if you feel more conservative, go with the 4.11 ratio. It’s still pretty good results!
Naturally, a duno tuning session at the same time is a reasonable idea. Lamar himself HAS an 03 or 04 SSR, and got his up to 270 hp via a simple dyno tune.
Feedback, opinions, and criticisms?
Jim G
I may also have mentioned to a couple of you that I run a small Internet business in which I use custom performance modeling computer software to determine for my clients what re-gearing they might do, to their cars or motorcycles, to optimize the performance for THEIR target use. Naturally, I applied the normal modeling process I use for my clients to my own motorcycles, and now to the SSR.
As it turns out, the modeling software predicts pretty impressive results in the case of the SSR.
To review a bit first, the stock 3.73 axle ratio in the SSR sounds impressive, but only until you remember that this is a 4800 lb vehicle BEFORE you add fuel, driver, passenger, and other load. In addition, the SSR, like all other vehicles made to sell in the United States, is geared from the factory to try to optimize fuel mileage for a better corporate average, rather than to optimize performance. Finally, we all have different target uses and preferences for our vehicles, and I suspect that maximized fuel mileage is not high on the priority list for the typical SSR owner, if it interferes with throttle response performance.
My own preferences and target objectives are a little sporty but pretty sensible overall:
1. I never cruise, for more than a few minutes, at speeds above 78 mph (I try to stay under 5 mph over the posted limit, which on the fastest freeways is 75 mph, to make myself an unworthwhile target for a police officer to paint with radar)
2. I DO like the periodic blast up to 100 mph or so, but only on deserted country roads where “there is no one in the forest to see or hear the tree fall”.
3. I do like carving along windy, hilly, narrow country roads at speeds that are “brisk” but not anywhere near pushing any boundaries
4. I don’t ever “race”, or really “speed”, on the street or anywhere else. I value my skin and bones, my low insurance premium, and the safety of my fellow drivers too much
5. I like satisfying throttle response in the 0 to 90 mph range, WITHOUT needing to force the automatic to downshift to get it
6. I normally like lightweight vehicles, so the heavy SSR is an exception for me (I fell for the retro styling and the untypical boldness for GM!!), and the deadened throttle response caused by the weight warrants addressing
7. I LIKE the sound of a higher revving engine – it makes any vehicle more exciting, and in the case of the SSR, that sound is pretty nice – like the sound of a Ducati motorcycle engine is!
I used these criteria to do some iterative performance modeling in my software, assuming MY weight and 13 gallons of gas, and learned a few things. I have found in the past that the quick shorthand way of best expressing what I learned, without the normal 9 to 15 page modeling results report, is by giving you some 0 to 60, 0 to 100, and ¼ mile times.
My stock SSR with the 300 hp GROSS / 250 (dynoed) hp NET hp 5.3 liter and stock 3.73 ratio, 160 lb driver, and 2 gallons of fuel:
0 to 60 mph:7.61 sec
¼ mile:15.84 sec at 90 to 91 mph.
0 to 100 mph: 19.39 sec
With ME and 13 gallons of fuel aboard (a more reasonable approximation of my SSR’s actual loading, those numbers become:
0 to 60: 7.86 seconds
¼ mile: 16.04
0 to 100: 20.10
Changing from the 3,73 to a 4.11 axle ratio, but keeping everything else the same:
0 to 60: 7.43 (0.43 sec better)
¼ mile: 15.76 (0.28 sec better)
0 to 100: 19.38 (0.72 sec better)
Changing from the 4.11 to a 4.56 axle ratio, but keeping everything else the same:
0 to 60: 7.03 (0.83 sec better than stock 3.73)
¼ mile: 15.54 (0.50 sec better than stock 3.73)
0 to 100: 18.60 (1.50 sec better than stock 3.73)
Then, I looked closely at the stock internal ratios of our 460 automatic (this is for 03 and 04 SSRs, remember – the 05 auto transmission is different I believe). The internal ratios are NOT designed for performance, but rather for flexibility and the EPA mileage test. There is a HUGE drop in rpm between gears, and a particularly disastrous one on the 1st to 2nd shift, that drops the rpm from redline down to only 3200 rpm. You can imagine how low the power output is at that rpm!
So, I tried upping the rev limit from the stock 5900 to 6200. That knocked 0.15 seconds off the 0 to 60 time, regardless of which gearing I modeled. With the 4,56 gearing, that dropped the 0 to 60, even with my portly body and 13 gallons of fuel, down to 6.9 seconds (a lighter driver with 2 gallons of fuel aboard would be appreciably quicker).
So, to summarize, if I go to 4.56 gearing, and also raise the rev limit (via LS Edit at the local tuning shop), I get the following improvements:
0 to 60: -0.96 sec
¼ mile: -0.65 sec
0 to 100: -1.65 sec
That’s a HUGE improvement.
The gear swap will be done at a well respected speed shop (Lamar Walden Automotive in Atlanta, where I am apparently going to stay on a temporary contract assignment for a year or so!). That shop has done lots of rear end changes and knows the subtleties of setting the clearances RIGHT (don’ t try this at home as an amateur). Done by these pros, it will cost $850.
Now, let me ask you, where else can you get -0.96 sec in 0 to 60 time, -0.65 sec in ¼ mile time, and -1.65 sec in 0 to 100 time for only $850 parts and labor TOTAL? THIS is the performance mod bargain in the array of choices.
Yes, the rpm at highway speeds does increae by 22%. That still only means:
2198 rpm at 60 mph
2564 rpm at 70 mph
2858 at 78 mph (my absolute highest cruise speed for more than minutes at a time)
These are acceptable. Check out the rpm at 60 mph for other performance oriented cars. This is higher than many, but not as high as some with engines of comparable capability and features.
Don’t sweat the fuel mileage either. If you haven’t yet read my earlier posting on fuel mileage on this board, you might want to check it out (“Incredible but true – gas mileage vs gear ratio test”).
I think this might be THE killer “bang for the buck” mod for 03 and 04 SSRs.
Or, if you feel more conservative, go with the 4.11 ratio. It’s still pretty good results!
Naturally, a duno tuning session at the same time is a reasonable idea. Lamar himself HAS an 03 or 04 SSR, and got his up to 270 hp via a simple dyno tune.
Feedback, opinions, and criticisms?
Jim G
