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I broke down and got a G-Tech RR so I could get a bit more quantitative in assessing SSR mods. It seems to have shown that the cagnge from the 3.73 rear axle ratio to the 4.56 was a GREAT idea.

To refresh everyone on the factory statistics, Chevrolet claims:
0 to 60 mph: 7.6 seconds
Quarter mile: 15.9 seconds at 90 mph.

Of course, unless Chevy did something way different than what is industry normal, those numbers are attained with a 160lb driver and 2 gallons of fuel in the tank.

Then, there’s the matter of vehicle weight. Sometimes, the factory specs are honest, and sometimes they are from a planet with less gravity.

The first thing I did was take my SSR to a CAT certified truck scale (They defend a trucker in court if he gets an overweight citation, so I guess they must be pretty confident of their accuracy). I was surprised, and delighted, to find that the SSR, me (way above that 160 lb “average” at 235 lb dressed for the street), and 14 gallons of fuel (86 lb), totaled to only 4960 lb. Working backwards, you can see that my particular SSR therefore weighs 4639 lb without me or gasoline, which is LESS than the factory spec. This is GOOD, as the SSR is a very heavy vehicle, and every 100lb saved makes a BIG difference (as you will see below).

Then, there’s the mattr of the shiftpoint. Yes, our 2003 and 2004 5.3 liter engines are factory redlined at 5900 rpm, but guess what, the automatic transmission starts its upshift at only 5600 rpm! (Something that the G-Tech proved beyond any doubt).

If you computer model an SSR’s acceleration as I have done, and substitute me and 14 gallons of fuel for the 160 lb factory driver and 2 gallons of fuel, you find that the statistics for a stock SSR become:

0 to 60 mph: 8.02 seconds
Quarter mile: 16.15 @ 89 (Excess weight DOES affect terminal speed as well as time)

I have had my rear axle changed from 3.73 to 4.56, and naturally wanted to know reasonably quantitatively how much it has changed the performance (seat of the pants says it has changed it a LOT).

It’s not easy to find a SAFE place to use a G-Tech, and it’s also darn hard to make certain that the section of road you are using is ABSOLUTELY flat. The problem with flatness is that it is very hard for humans to accurately judge, and even a little elevation gain or loss will hurt or help the acceleration performance a LOT, especially when the vehicle weight is such a big factor to begin with (Most “performance” vehicles are 1000 to 1500 lb lightr than an SSR, or looking at it another way, our vehicles are 29 to 50% too heavy for this engine to be able to qualify as “performance” ready).

To show you the magnitude of the problem, a 5% grade on a freeway is considered VERY, very steep. 2% is very noticeable. 8% is a mountain pass type grade. But, when you run the math (which gets a little tedious so I won’t bore you with it), it turns out that a 2% downhill grade will affect the 3rd gear performance of an SSR significantly, as it artificially adds almost 14% “acclerating force” to what the SSR is producing itself after deducting the force used to counter air drag at 3rd gear speeds. How much would that change a 0 to 60 time and a quarter mile time? I’m glad you asked, because I did the tedious modeling to find out, and it’s a big effect. Turns out, it reduces 0 to 60 by almost 0.4 second and quarter mile time by about the same amount. I mention this not out of academic interest, but because it will loom significantly below. Remember, the difference between 2 acceleration runs, one taken accidentally on a 1% upslope (pretty undetectable by a normal human), and the other accidentally taken on a 1% downslope, is 2%.

With all that preamable, I found what appeared to be 3 spots this morning that LOOKED flat and seemed safe. The 1st run turned out to be a bad run, as I got a bad launch AND had to shut down pretty early when a vehocle appeared out of nowhere (when at full throttle, I want NO vehicle anywhere within ¼ mile of me). The 2nd run seemed good, and I was able to complete an entire quarter mile. The 3rd run, in the opposite direction, went even better (too well, looking at the results?)as I started to get the hang of launching without too big a bog. The results are below:

Statistic / 1st run / 2nd run / improvement over 3.73 gearing

0 to 60 mph / 6.99 / 6.48 / 1.03 to 1.54 seconds

Qtr mile / 15.48 at 89.9 mph / 14.99 at 96.9 mph / 0.67 to 1.16 sec and 1 to 8 mph

I was of course deeply suspicous of the differences between the 1st and 2nd runs. The differences were pervasive throughout the the 2 runs, and so could NOT be explained as a betetr launch for example. The 2nd run showed better acceleration everywhere. I checked the wind reports for that time of day. 3 mph or so, so should not have been a factor. I have to assume that there HAD to be a grade difference between the 2 runs, even though they both LOOKED “flat”.

My post-run computer modeling verifies that a 2% differential between the 2 runs would be all that is needed to create this kind of difference between the 2 runs. I apologize for an obviously inadequate sense of levelness.

The computer model predicts that the difference between the 3.73 and 4.56 runs, using the actual 5600 rpm shift points (instead of the ideal “as high as possible” with this “wideratio” set of gearbox ratios) should be about:

0 to 60: 1.12 seconds difference
Qtr mile: 0.67 second and 2 mph

So, I am right in there in terms of actual results, with the 1st run being much pretty close, and the 2nd a little “too” good.

Even in the absence of precision, a few things are clear:

- The improvement in performance is BIG
- On a bang for the buck scale, this is awesome
- You CAN get an 03 or 04 SSR 0 to 60 time into the 6’s
- The regeared vehicle feels WAY better than the raw numbers even suggest. It actually feels “nimble”!

Jim G
 

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Discussion Starter #2
If anyone intends to copy what I have done:

- The improvement in performance varies a bit with weight, with a heavier vehicle or heavier driver making the difference BIGGER, and a lighter vehicle and lighter driver making the difference SMALLER (but not MUCH smaller).

- Expect to pay about $850 for the gear swap, parts and labor, BUT make sure you have a good, experienced shop do it, as it requires great precision to keep the noise level of the steeper gearing acceptable. My installer followed the gear manufacturer’s clearance instructions (0.006” or 0.008” as I recall), but we later realized that the manufacturer probably anticipated racing use, rather than street use, for a 4.56 axle, so probably set the specs loose to minimize power loss. For the street, you want more QUIET than that, so you can hear that nice exhaust note that is even nicer with the stiffer gearing. So, my installer is going to redo the backlash clearance, tightening it by 0.002” to see how much that improves it. We base this plan on the fact that the axle is VERY quiet once it warms up at highway speeds for a few miles, but is noisy when cold or at city speeds. That suggests that thermal expansion under load is eliminating excess clearance that makes the audible noise.

- Be sure to use “Moroso Climbing Lube” as the lubricant in the rear axle. It quiets the ring and pinion noise of the steeper gearing a lot. The cost difference is probably $40 or less, so just DO it.

- Be sure to get your thinwalled, aluminum, “noise chamber trumpet” driveshaft quieted down by having it PROFESSINALLY cut open, filled with expanding foam, rewelded, and rebalanced (!!) to make a BIG difference in its noise amplification properties. Expect to pay $125 to $200 extra for this depending on the local market. Do NOT cheap out and get the cardboard sound deadner. Get the foam! Get it done while the shaft is already off the ring and pinion change to save duplicating labor.

Jim G
 

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Exile

Hey Jim

Sounds like you're having lots of fun in exile. I enjoy reading all your posts. You going to be able to help me improve the performance of my baby upon return? Watch out for the predicted hail today as we got it Friday nite.

Your "ex" neighbor Richard :seeya
 

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Discussion Starter #4
Yes, I am watching today's weather very closely, ready to put the SSR under cover with a few minutes notice. Very unstable climatic conditions here in Atlanta today.

Jim G
 

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Jim,

Just had a HUGE hail storm here in Waleska. Golf ball sized, but it only lasted 5 minutes!

Thank God Miss Daisy was in the garage!
 

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Discussion Starter #6
Buffy: My SSR is under the hotel lobby drive-up entrance roof for the evening and night!

Jim G
 

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Tink and foam

Does anyone really have an answer for the tink in the drive shaft. I have just pulled mine out of storage for the season and have been trying to get it to make this noise with out success (Good thing or bad thing?). Dealers say it's a bad shaft and replace it but yet some still have the problem persisting after replacing it. Jim say the shaft is like a trumpet and carries the sound up from the rear end. His statement about filling it with foam makes sense as far as cutting noise down but is there really a problem with the original shaft? Has anyone ever broke a ujoint or had severe wear?
I have been reading Jim's thread on 456 gearing and really intreagued by it and would not want the whine heard up frt. Like to fill shaft with foam but not if it is a bad shaft
Like to hear some comments on this thanks :confused
Doug :thumbs
 

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I don't think there is an answer yet for the tink. I had my original one replaced with the "new, improved" version. Within a few hundred miles the tink was back. I agree that the shaft is like an echo chamber. Tap it with a wrench and you will hear almost the same tink sound. Wildcat mentioned something about GM experimenting with a newer design that has cardboard baffles inside. Haven't heard any more on that yet. The present replacement is not fixing the problem. This is going to cost GM not just once, but at least twice for warranty work.
My service rep mentioned that this was a problem on another vehicle a few years back. What they did was to insert a valve spring into the rear slot of the tranny, pack it with some heavy grease and then slide the shaft in. The grease and spring got rid of the play in the shaft and stopped the noise. This might not be GM approved but it worked.
I understand that the tink, although annoying, is not any problem mechanically. I keep asking if anything new has come up when I am at dealer and will wait for GM to come up with version #3 and have mine replaced again.
 

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Discussion Starter #9
I've had the new driveshaft with the "donut" (dampener) on the front for about a month now, and the tink has not returned - at least yet.

Mind you, now that my drievshaft is also foam filled (at MY expense), I might not even HEAR the tink if it returns.

Jim G
 

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Jim I am thinking about installing the 4.56. Could you tell me what gear it is from Motive. I have been checking and not sure what rear end it is. I was also wondering if you could give me the number of the shop that installed for my speed shop to call if any questions. Thanks for all of the work.
 

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Discussion Starter #11
The Motive Gear part number is MTV G885456

Be sure to get this precise part number, as according to the tech guy I talked with at Motive, this is the QUIETER version of their ring and pinion line. They refer to it as the "orange box" line, as opposed to the louder blue box line.

Also, make sure your installer sets the backlash to the tight end of the allowed range (around 0.006") as it can sometimes loosen with breakin, and that makes it louder.

Also be sure to use Moroso Climbing Lube as the lubricant, as it helps quiet the noise.

My installing shop was Lamar Walden Automotive in Atlanta, at 770-449-0315, but you should not pester Lamar with questions, as he is not going to be the one making the profit on YOUR install. He should be regarded only as a tech resource, if needed, for your installer. Don't expect him to be your installer's teacher. Rear ends take a LOT of experience to do correctly, so find an experienced guy. Don't piss off MY valued technical resource with questions on a sale with which he has no connection!

I am dependant upon Lamar's goodwill, as he is going to actually disassemble my axle again to recheck the clearance, and tighten if it has loosened.

The Motive Gear number is 800-934-2727. THEY are your more legitimate contact, as they are selling your installer the gearset.
 

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Too Few Gears

Congrats on getting a responsive gear setup. If the automatics had more than four gears, it would not have been necessary to spend that money. It is unbelievable that GM is still selling Vettes and SSR's with stinkin' four speeds when others offer 5, 6 and even 7 speed automatics. Does anyone know when GM is coming into this century on this? It reminds me of the old PowerGlide days when they kept selling 2 speeds while others had 3 speeds.
 
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Taking the plunge as well...

I sell Motive gears at my shop so I'm glad to hear Jim had a good experience with them. I'm going the same route with my '03. One of my customers owns a 1/4 mile drag strip that I sponsor and have access to, and I'll be doing a bunch of actual before and after timed runs to back up Jim's numbers. Will also be posting results of other performance mods as well with the same vehicle - I own an aftermarket shop and am interested in verifying manufacturers performance claims for what I sell.
 

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Large Eaton Rear Gears?

There are a few of out here that have the '05 six speed with the larger Eaton rear. Without looking, I assume it is the same as the "14 bolt" truck rear??
I also expect the performance gains would be similar with a gear ratio change. I someone making gears for us as well?

Thanks
 

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Discussion Starter #15
psychoslaphead: I see that you are in Lee Summit, MO.

I spent a LOT of time there last year on a contract assignment involving Aquila Energy, so know that Missouri is a HOTBED of street rod action. Nice location.

There are a number of us on this website that would be interested in performance mods. I srated out vowing to just leave the SSR stock, as after riding 10 second bikes, ll cars are slow, but it's just irresistable.

Jim G
 
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Jim,

Small world - I used to work for Aquila. What did you do for them?

I'm planning on installing and testing:

- gears
- exhaust
- programmers
- intake
- either turbo or blower, not sure which yet


also suspension mods

- RJ
 

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Discussion Starter #17
psychoslaphead: I was the project manager on an enterprise software integration project for their customer service call centers. I was retained by MITEM Corporation who had won the contract to do the project.

I am especially interested in what effect the follwoing would have, and how easy hard to get installed:

- Headers
- Exhaust
- Vararam or other intakes
- rear mounted turbo (as mentioned in another of my posts)

Jim G
 
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I'm planning to start ordering parts next week...can't wait to get started :)
 

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Thanks Jim. I appreciate the info. I had no intentions of calling your installer. So dont worry about me PISSING him off. I only needed the number if my install guy had a question. I doubt he will need to call him as he also knows how to install gears. Thanks again I appreciate all of the tech work you have done. It made a differance in my decision Russ
 
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