irocz28_350

iTrader: (1)

How many 3rd gens came with the aluminum driveshaft?

TTOP350

iTrader: (8)

mostly 350 auto, 305 5sps and cars with performance gears.
As far as a number? I doubt we'll ever know 4 sure

JamesC

iTrader: (5)

But many. They aren't uncommon at all. I once sold 60+.

JamesC

TTA 1387

They were also used in LT1 M6's when owners complained of vibration. I still have mine that I got in late 96

firehawk1988

My 88 Formula 305TPI auto came with the aluminum driveshaft. I freaked after i bought the car and noticed the shiny, non-rusted shaft. I checked my RPO tag and there was the JG1 listed. I was surprised since the car had the common 305 TPI auto, rear drum brakes, and single cat exhaust. But having the WS6 suspension, 3.23 limited slip rear end, and two tone paint delete(WX1) might have helped. My car option wise is nothing special, but the shaft was factory and its nice to know its there....lol

TX T/A

iTrader: (1)

I want one for my 92 convertible. U would think the ws6 trans am would have one automatically

Drew

iTrader: (58)

They were used to save weight, not improve performance.

GICATA

By saving weight performance is improved. Supposedly they were easier to turn.

Drew

iTrader: (58)

The performance difference is negligible. You're not going to be able to feel the difference between a steel shaft and aluminum shaft from behind the wheel of the car.

The aluminum shaft is lighter, so if the options on a car were starting to push the limit, GM could option the aluminum shaft to make the car pass CAFE standards when it normally would not. Many thirdgens with most/all performance options don't have the aluminum shaft. Yet they show up on cars with 2.73 gears, t-tops, etc (heavier, lower performance cars).

okfoz

drew is correct,
The majority of things that were done to 3rd gens (especially) in the later years were in fact a result of weight savings...

Examples:
In 1987, you could not buy (in the US) A GTA with a 350 and the rear shade or the sub-woofer system...
In 1987 - 1988 you could not buy a T-top/350 Pontiac
From 1990 - 1992, only the Formula was available with T-tops in 91 & 92.

The aluminum drum brakes in 1991 when there was a disc brake shortage was more for weight than performance, although aluminum drums do stop better than cast iron, because they dissipate heat better than Cast Iron.

The drive-shaft spinning weight would be good for at most 1HP... barely worth the cost... The N10 dual cats are a much better upgrade, probably good for 5-10 or so HP, so not everything fell into that category...

John

JT

iTrader: (1)

Compnine shows all 663 Trans Am Convertibles for 1992. As an owner of one of those, this was one thing I looked into. I noticed that none of the LB9/5-speed received the JG1 option. Not even if it had WS6. JG1 was only found on the LB9/automatic, and only slightly half of them that had WS6. It would support Drew's comments, as I think there is little argument that the LB9/5-speed was the "performance" drivetrain over the LB9/automatic.

TTA 1387

It doesn't add HP, it just frees up HP. Rule of thumb was 10lbs recipricating equaled 100lbs static. Plus the 1LE had a higher speed rating, IIRC.

Drew

iTrader: (58)

Go ahead and run a car on a dyno with a steel shaft, swap to an aluminum shaft and run the car again, and let us know how many HP you freed up. Do the same test at the drag strip. It won't make any difference. If you can't measure it, you aren't going to feel a performance improvement from behind the steering wheel.

chazman

iTrader: (4)

I've got an '89, LB9, T5, N10, 3.45 gear IROC-Z coupe and I have the steel shaft. I agree with Drew, that they were installed on cars which were pushing their CAFE weight class.

I've also seen dynos where they were worth about 1 hp at the wheels. They apparently have less vibration at high speed though and were installed under warranty if the customer complained about that. I wish I would have known that back then!

I've bought an aluminum driveshaft a while ago but haven't installed it yet.

okfoz

1) A drive-shaft does not reciprocate. By definition a reciprocation would imply something that goes back and forth like a piston. A drive-shaft typically spins in one direction and does not change direction quickly, there are centrifical forces at work however... With that said, a vibration just consumes power, if your drive-shaft or any other part of the drive-train has a vibration in which it was not well balanced that vibration will consume power like no tomorrow. An example of this would be a spinning top, a well balanced top will spin for quite some time, but one that was made in China and slightly off balance will topple over much more quickly..

Once a drive-shaft is put into motion the difference in consuming horsepower via a 100# or a 1# shaft would be virtually null... Something reciprocating would consume much more power... IIRC, the amount of HP to sustain a speed of 55mph is about 35hp for a typical car... Therefore the benefit would be for acceleration only, possibly braking...

One thing to consider is that an Aluminum drive-shaft may be easier to balance. You would need less weight in order to get it properly tuned. Most reports I hear is that those that have installed an aluminum shaft say it is better balanced, more than any noticeable power increase.

2) I had no idea that our cars had a "speed rating" 1LE or not, the only speed rating that I am aware of was based on the tires... Ultimately the performance differential was more with the performance gear option than anything. Many of our cars did have a ECM limiter for speed, but beyond that....

3) Learned on the Discovery Channel... or was it the Learning channel.. whatever: For every 10% in weight reduction there is an 8% increase in fuel mileage.

4) Ultimately it would be more beneficial to the reduction in overall weight than the reduction in the spinning weight of the shaft. The benefits are correlative, but ultimately the loss of 10# static weight was more significant than the loss of 10# in centrifical losses...

4) Racers Rule of thumb: For every 100# in weight reduction means .1 sec in the quarter mile. AND Every 10HP increase is .1 sec in the quarter mile (to a point) not really sure if I buy into the second one...

TTA 1387

You can measure it but you are right about feeling it. This is when Keith used to do everything on the dynojet to see what stuff did. Not much of a gain but a gain nonetheless.

http://ws6.com/mod-1.htm

KMK454

I'm surprised there's so much debate about the merits of an aluminum driveshaft... any part that is lighter in weight is highly beneficial to performance, especially if it's a part that the drivetrain must rotate such as a driveshaft, flywheel, or rim.

An aluminum driveshaft does not give an engine more horsepower; what it does is reduce drivetrain loss so that the actual power seen at the rear wheels is higher. However, on our 180-245 hp thirdgens, this isn't something we'll notice on the dyno. We might see a 1-2 WHEEL horsepower (not crank) gain, but that's it. So if you're looking to do a performance mod for a street car, there are better things to do first. I still think it's cool to add all the factory things, like 1LE brakes, aluminum driveshaft, etc., and if you have the parts and will why not?

TX T/A

iTrader: (1)

I'm sorry but when I said I wanted an aluminum driveshaft I meant that I wanted it because of its uniqueness. I think it's cool when GM installed trick parts for whatever reason. As far as weight savings ,I'm all for that with my convertible. True performance in my opinion would not come from a few pounds shed, it would come from engine mods,etc.

UnderCover89TBI

iTrader: (25)

My car felt better when I switched to a aluminum shaft. It seemedt to rev a little better. but I got mine for 30 dollars so it didnt cost much.

Drew

iTrader: (58)

Ford Aerostar minivans came with aluminum driveshafts... Pretty trick parts there...

Lay off the supersize when you order your value meal for the next 6 months and you'll go faster then swapping to an aluminum shaft.

JamesC

iTrader: (5)

I swapped in an alum shaft long ago. I have no regrets. If you want one, for whatever the reason, go for it.

JamesC

camarokracker

iTrader: (1)

X2

Brother Al

To add to the weight case, I found one in a low mileage '91/'92 Firebird V6, my original theory was that it was a way to dump excess inventory... but the whole JG1 usage mystery does seem to be supported primarily by the weight reduction by GM to meet CAFE, instead of for performance...
Same goes for the use of J42 aluminum drums, and the aluminum front bumper braces in the '82-'84 Camaros and Firebirds... and all of the oddball '78-'88 G-Body and Caddy parts made of aluminum...

UnderCover89TBI

iTrader: (25)

id like some aluminum drums! I have a buddy with an 80 olds cutlass diesel and he has an aluminum hood..i was like wow!

okfoz

Aluminum is more expensive than Steel, Aluminum pieces became more popular in the late 70's around the time, or just before the Govt started mandating CAFE Standards... The earliest car that I can really think of is My 77 Buick Electra Limited had bumper brackets made from Aluminum, the only reason was to save weight... I would be interested to see that there was a V6 JG1 car out there, without a SPID, its only hearsay at this point, it would definitely be an interesting conversation piece.

Buick even had an Aluminum block back in the 60's so it is not all that new, but in the time when they are trying to make the cars cheaper, it does not make sense to add the extra expense...

okfoz

I had a guy try and trade me a Buick Regal Diesel with T-tops for a 1991 Formula I had... I was like... umm... no!, I wonder if it had an alum hood.

firehawk1988

I see alot of good points made here. If you are looking for performance parts, there are other things you can get to increase your power. If you want an aluminum shaft for the idea that its there(the coolness, the uniqueness, trick factory), then like said above....go for it.

As far as a performance advantage, it would be small since we are talking about street cars with under 190 rear wheel HP. You have to remember GM was always working on new ways to squeeze as much performance out of these aging chassis's to compete with the 5.0 Mustangs.

Rotating weight is a factor in performance. In Oval racing( and drag racing too) you will see aluminum flywheels for manual transmisions to help the engine rev quicker to get to its HP peak and the right power band for the track. Light tires, wheels and other drivetrain components helps free up the engine. Hot Rod magazine did an article in the mid 90's that showed the differences in weight loss, both static and rotational.

The formula of 100 pounds is equal to 10HP or .1 sec on the track is pretty close. Years ago I had a Toyota Supra( yes, i know its rice...lol) and at the track i had both my K&N filter and the stock filter with duct work that ran to the airbox. For fun i wanted to see the difference and the K&N was .1 sec quicker each time. This goes along with the advertised "up to 15HP gains" putting me close to a 10HP difference. I tried this on multiple runs both in the day and evening(to account for track and air temps). The car was real consistent either way. I haven't been able to try the 100lb weight lose theory yet( spare tire and other items wasn't close).

I used to race R/C touring cars at the semi-pro level and the theory of rotating weight went the same for them. The motors were limited by the rule restrictions so freeing up rotating weight gave the cars more speed and acceleration. Me and my brother made custom driveshafts for our cars. The cars were 4wd and ours had a solid aluminum shaft connecting the front and rear diffs. We made hollow aluminum shafts ( 3 ozs dropped to .5 ozs) and that alone made a difference. The cars had to have a static weight minimum which we had to add weight to the chassis. I know it sounds strange to remove weight to the add weight, but i read in the same Hot Rod article that losing rotating weight is valuable. Taking away 20lbs of rotating is better then 20lbs of static. Look at race engines. Lighter cranks, aluminum rods, lighter valve trains....all to help the engine rev better and free up HP.

I know i'm rambling on but I figure the aluminum shafts for our street cars is more of a cool factor now compared to all the other mods thats available now. Too each his own and no matter what, always enjoy your F-body.

the bandit

I read that steel drive shafts weigh 20lbs. and aluminum shafts weigh 11lbs.I have 1990 GTA street/strip car with a 400hp 350 that runs 12.20`s on slicks.What would an aluminum shaft do for me?

White93z34

iTrader: (1)

I bought a JG1 driveshaft years ago, just installed it in my car last fall, I noticed acceleration was slightly smoother then before... then again the original steel driveshafts u joints were kinda worn out whereas the ones on the JG1 driveshaft were in much nicer shape.

luvofjah

iTrader: (2)

I thought I read here years ago that at a certain speed the steel drive shaft would vibrate... and that the speed at which this occurred for the aluminum drive shaft was much higher (being made of aluminum, not steel). So this also fixed many people's vibration problem too...

Rafael

okfoz

About .01 sec.

Rule of thumb, For every 100# reduction you gain .1 second quarter mile.

John

Aaron91RS

iTrader: (2)

that's only a good rule of thumb maybe for the people who are going to stick within a couple hundred pounds of stock and unsprung weight at that.
Start removing rotational weight and it's a whole new ballgame.

By that formula a 1lb fbody would only go from a ~14sec car to an ~11sec car.
I'll show you 3000# fbodies in the 300-400rwhp that go 11's all day.



A Camaro with 235/60/15 (26.1" tall) tires and a 3.42 rear gears traveling at 70 MPH will have a drive shaft
rotational speed of 3084 RPM. At 100 MPH the drive shaft will be turning at 4406 RPM. Critical speed for a factory 3" steel
driveshaft that is 50 " long is 5790 RPM. 85% of critical speed is the maximum speed you should turn a driveshaft. 85% of 5790 =
5340. You can see that 4406 RPM is well within the limits for this driveshaft. If you change the rear end gears to 4.11, the 100 MPH
driveshaft speed increases to 5295 RPM which is bordering on maximum critical speed. Having a driveshaft operating at 50 to 60%
of critical speed will run smoother with less vibration than one operating at it's maximum.

yep 91 lb9/auto/ta/ws6/vert here. Has the aluminum driveshaft.

82z28 wrencher

i agree to disagree lol a AL driveshaft is a impovement over steel. Its for the simple fact it is lighter and that it will free up the driveline. The less wight the engine has to rotate the better it will be. Sure such a small impovement may not be noticeable but add a light flywheel imporved trans and pehaps a spool in a axle and disk brakes u will gain in less drag resistant impoving rwhp.

every bit helps thats like saying dont get a aftermarket carb sure ull gain 4hp but combined with many imporvements it will be a great overall improment.

but just my opinion lol i also agree its just cool i thought my AL drums on my 82 z28 was cool

okfoz

A Rule of thumb, by definition "A rule of thumb is defined as a general guidepost for determining behavior, or a rule that allows one to make a quick mathematical calculation or remember a formula. The rule of thumb exists to recall something else, whether general or scientific in nature. In standard usage one might write: A rule of thumb in fashion is to never wear white after Labor Day. One might also substitute “in general” for the phrase rule of thumb." - Wisegeek.com

It was meant to be merely an estimate. A While back I think someone did a RWHP test and found the benefit to free up 1 HP. Which if true would not even be noticeable in acceleration department. There are a myriad of things that would give you better HP improvements. However every bit counts, and the reduced un-sprung weight would help with the attitude of the suspension. There is no doubt there are several advantages to the Alum Shaft.

John

eseibel67

What is the RPO code for the steel shaft? SPID sticker does not have the JG1 shaft code, but the car does have an aluminum shaft. Must have been a dealer warranty job.

okfoz

Not sure if it actually has an RPO... Keep in mind that "RPO" literally means Regular Production Option. So the codes in theory could indicate the options on the car. Since the Steel shaft was standard, there may not be an RPO. When things get more complicated IE 3 suspension options, or multiple axle ratios, it would make it more necessary to actually have an RPO for all options. Other examples of things that there is no RPO are without Door locks, or without power windows. On the other hand there is a stripe delete RPO, but note it is a stripe delete, therefore it was an option to delete the stripe, and there was also an RPO to indicate the color of the stripe, because there were multiple stripe options for any given year.

SCCAjunkie

BTW- just from a purely physics standpoint, the change in moment of inertia (the effective equivalent of mass in a rotational system) from steel to aluminum driveshaft is *roughly* the same as removing 1.5 ounces from each of your four 16" wheels.

I'm getting one when I can anyway, simply from the better balance/ higher critical speed standpoint. I run 3.42 gears and 25.7" tall tires, and since I instruct at track days, the car may see better than 125mph. This puts me way above the numbers that Aaron posted above (I'm assuming his calculations are good), so it's something I think is quite important in my particular case.