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Discussion Starter #1 (Edited)
A roadtest article on the Trailblazer SS in the Nov/Dec issue of Truck Trend, when analyzed closely, provides lots of useful and puzzling data relevant to SSR owners, on transmission, gearing, towing capability, fan power consumption, and engine power.

Transmission:

The SS is shown as having a "4L70-E" versus the 4L60-E on the 03 / 04 SSR and the 4L65-E on the 05 / 06 SSR. The gear ratios in tis transmission are identical to the ones in the 4L60-E and 4L65-E (including that bad large gap between 1st and 2nd), but I've been unable to find out what the other differences are. Presumably, the 70 is stronger than the 65 which was stronger than the 60.


Gearing:

The article implies that GM has seen the error of its foolish ways on gearing, and has seen the light. It has apparently installed 4.10 gearing on the SS. Comparison with the SSR is relevant.

The internal gear ratios of the transmissions on the SSR and SS are identical.The 295/40R20 tires on the SSR have a diameter of 29.25 inches, and with its 3.73 axle ratio give 1798 rpm at 60 mph. The 255/50R20 tires (same Goodyear model, but not size, as the SSR!) on the SS are 30.0 inches in diameter, and with the 4.10 axle ratio give 1929 rpm at 60 mph, about 7.3% more than the SSR. This is a pissy weak improvement, but nevertheless a move in the right direction. They were probably just a little shy of the 2145 rpm at 60 mph that a 4.56 would have provided, and maybe concerned about how bad that aluminum driveshaft would sound at the higher rpm. :)

By the way, the SS uses the Torsen differential, even in the all wheel drive version (SS comes either 2 WD or AWD), so I guess GM has sold itself on this superior differential.


Towing Capability:

The 2WD version can tow 6800 lb. and the AWD version can tow 6600 lb (the AWD version of the vehicle weighs 200 lb more than the 2WD version, explaining the difference). Truck Trend attributed this high rating to the engine-driven mechanical versus electronic fan that our SSR has. In fact, it says that GM put the mechanical versus electric fan there specifically for that reason. They fail to mention of course that the underhood SPACE and VENTILATION is far superior to that on our SSRs too!


Fan Power Consumption:

Truck trend says that the 395 hp rating of the SS versus the 400 hp rating of the GTO and Corvette (and SSR) is due to the extra 5 hp that the mechanical versus electric fan diverts.

I am willing to believe this, as 5hp translates to about 3750 watts, or at 12 volts, about equivalent to an electric fan that pulls 312 amps! This is roughly 10 times the power draw of the electric fans on our SSRs!

Engine Power:

This is where it gets really puzzling.

The SS suppoesedly has 395 hp - almost the same as the 400 hp in the 05 / 06 SSR. And, the SS 2WD version they tested is notably lighter than the SSR. apparently weighing in at 4552 CURB weight (that means with fluids, but no fuel) versus 4725 for the SSR - about 4% lighter. And remember, it's running 4.10 gearing versus 3.73! I would therefore expect it to be notably quicker than the SSR. Because the SS and the SSR also share virtually identical chassis's, this is about as close and fair a test as you can structure for 2 different vehicles.

However, the magazine reports a 0 to 60 of 5.6 seconds, and quarter mile of 14.2 at 98 mph, both of which are slightly slower than the 05 / 06 SSR with automatic. Furthermore, the 98 mph terminal velocity versus the 100 mph of the SSR verifies MORE than a 5 hp drop in power.

Interestingly, the 5.6 zero to 60 time beats Chevy's own claim for zero to 60: 5.7 seconds.

The same magazine got an identical 5.6 second zero to 60 time when they tested an 05 SSR in the August issue, and their road test summary section does not provide the quarter mile time or terminal velocity, further muddying the water.

It ight be interestig to chase down these discrepancies if anyone has more time available to do it than I do.

Anyway, that's what I've pciked up so far out of this approximately one page of text road test . . . :)

Jim G
 

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Resident Rocket Scientist
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Thoughts

Jim,

Perhaps it's not one big thing but a series of smaller changes that make the SS slower than the SSR. First things that come to mind are a non aluminum driveshaft and heavier wheels. I don't know if this is indeed true but that would explain at least some of what the 0-60 times are about the same but 1/4 mile is not, having overcome mass moent of inertia in the driveline.

For now it's just ideas..
 

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Las Vegas Mob
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Torque management profile? Just musing out loud here. This is the first reference I have heard of a 4L70-E. Very curious/interested if it is a stouter transmission. As always, great info Jim. :thumbs

Blast
 

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4=speeds(4)
L= longitude(rear drive)
70=strength(higher the #, the more torque it can handle)
E= electronically controlled
 

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Discussion Starter #5
41Chevcoe: Yes, you are correct in your decoding of the model numbers, BUT the model numbers don't tell yuo specifically what waas changed, nor is the "70" any numerical indication of strength - it's merely a series number. What we would like to know is the input torque capacity and the internal torque capacity, as described for the 4L60-E and 4L65-E in my book.

I have been told by a pretty reliable source that the torque management on the GM engines has, at least in the past, applied only during gearshifts. Perhaps that has changed?

Remember how some SSR ownrs with later 05s or reflashed 05s complained that their "torque meter" on the accessory panel no longer goes as far to the right as they have seen in the past. I wonder if GM is toning them down to protect that driveline.

Jim G
 

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SS vs. SSR

Just took delivery of a new SS this week. Still have my SSR. The transmission sure is much smoother! As far as power, it is still to early to say. The SS is cerrtainly quick-----but so is the SSR. I will wait until it is broken in a bit to hit it.
 

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Retired GM Program Manager/ Chief SSR Engineer
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The SSR Transmission was tuned for more aggressive driving. The 3.73 axle was used because of axle strength issues that were unresolved when we had to go to '05 production. The rear tires of an SSR have a lot more traction than those on an SS and this is the reason that we had to have the larger axle for the manual transmission.
 

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I too have been watching the new TB SS and am real impressed so far. I have seen posts on the performance truck site that they only got 300 "AWHP" out of one of them. I also understand that there are not very many changes to the transmission, as yet to be discovered. I did see where there are a few that are getting into the programming and there is alot of Torque Management as with any automatic to save the drivetrain as discussed by JimG above.

Overall I think it is a great vehicle that should hold true to the SS nameplate.
 
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