I looked at the RPO codes for my car. It's a 1987 with a G44. Also has an automatic transmission. G44 is described as a performance rear axle. Performance? Why performance? Seems to me, 3.45 would be performance, where you get the low end boost. As far as I can tell, Corvettes have little trouble at the top end. My car is a bit weak at the low end. I would think 3.45, or even a 4.10 would be the way to go? What am I missing?

 

Stock auto coupe came with a 2.59(RPO GM1). I think 3.73 was also an option.

 

Ok, so relative to a 2.59, 3.07 is performance. That makes sense. To go to 3.73 from 3.07 is it just a gear removal, (same housing), or is it a complete axle replacement?

 

you need to change the ring and pinion and you'll need an install kit as well. The gears are $400.00 and ther install kit is $100.00

 

And the gain is about .5 sec in the 1/4 mile? Have you done this?

 

i have the GM3 rear (3:45's) on an L98 6speed. I'm torn between moving up to a set of 4:10's or throwing in a set of headers and maybe roller rockers and an intake. Everybody you talk to says something different... so what do you all think...leave the 3:45's and go motor or leave the motor alone for now and go with a set of taller gears?

 

That'd be a set of "shorter" gears....but, the choice is yours. Why not do all of the above???

Larry
code5coupe

 

[QUOTE=rocco16;1559035743 Why not do all of the above???

Larry
code5coupe[/QUOTE]

No problem...just pm me with your AMEX # and I can get started!

 

[QUOTE=DaleD;1559032672]And the gain is about .5 sec in the 1/4 mile? Have you done this?[/QUO

I did a gear swap in mine, I went with a 3.73 but I have a LT1
It made a huge difference but that's not comparing apples to apples.
The L98 guys will know what gear you should run better than me. I'll help you pull the rear end though !


gears $ 400.00
install $ 100.00
labor $ 200.00
misc. $ 50.00 gear lube,posi additive, gasket sealer

 

On a street car I would stay with what you have with your L98 motor. If you want a bump up no more than 3.54 or 3.45 (can't remember which one is for your carrier). You will not be happy with a 3.73 or lower IMO.

 

The 3.07 was the "performance" ratio in 87 for the auto and the only ratio for the manual tranny. The G44 denoted the specific gear ratio (3.07 in this case but the ratio for G44 changed thru the years based on what GM offered for optional ratios). The standard ratio for the auto tranny car was 2.73.

Later C4's used an RPO G92 that represented the "Performance" option and not a specific ratio. The optional ratios had their own RPO numbers. Do you also have RPO G87 that represents the Dana 44 8.5" ring gear??

The 87 with either the A4 or the 4+3 should be capable of top speeds in the 150MPH range and quarter mile times in the mid-13's and 100+ trap speeds. The L98 makes its power in the middle of the RPM range but begins to die off quickly above 5000 RPM. Changing the gearing on an otherwise stock motor will increase low end acceleration, but top speed will suffer.

 

The L98 is a little torquier than the LT1, from what I've read. 3.73 should be good?

 

3.73 + A4 + L98 = screaming RPMs.

The 3.73 just strikes me as being a little too short.

I would go no farther than a nominal 3.45 with an L98, but that's me.

If it was my $$, I would save the money, and invest in a used D44 with the stock 3.42 gears. More gear in a D36 will ulitmately = bad things...

For now, stick with the stock 3.07 and do some tricks to the engine. You have a lot of room to grow there before you run out of gear. And the more you do to the engine, the more you will want that D44.

See what I am saying? It's all about managing the resources at hand.

 

No, not on an 87. More than likely you'll lose time.

An L98 does not need more than 3.07 with the automatic.

 

Ok, clear as mud.
So, either it will make a big difference to the plus, no difference, or be a minus.

 

I think you have to pay careful attention to people's combinations when you see them saying that a gear change netted .X in the 1/4mi, because they wont always point it out to you.

LT1s are a different animal than L98, they respond very well to gear changes. They'll gain 0.5s easy. People with modified engines may have selected something in particular to augment the setup.

I think stock/near stock-L98 owners with A4s should never go lower than 3.07. It will not make a big positive difference in ET unless you've really messed with the engine.

 

Lets ask what gears do:

1) they allow for greater acceleration, because the engine is allowed to reach it's power band faster and multiply that power better.

2) If your gear selection is numerically too high, then there will be trouble - the engine will never be able to run enough to keep up with said gear.

3) If the gear is low, numerically, then acceleration is harmed because the engine is unable to rev up fast enough. It will get top speed, tho.

Remember, the L98 runs out of gas at ~ 5000 RPM. If the engine is working that hard all the time, you are working at the wheezy end of the rev range... not very efficient.

If the engine has more revs available, you can take advantage, as long as the engine is putting out more power.

Three cars, three different power bands:

1) 1987 Vette (A4, 2.59 gears). This is my wifes car. The L98 is torquey down low, but wheezes up high, it did all of it's street based driving work below 4000 RPM.

2) 1992 Vette (M6, 3.42 gears) My Vette. The LT1 runs up to 5700RPM or so. When used on the street, I never work it much past 4500 RPM, but it would pull solidly upto about 5500 RPM.

3) 1994 Honda Prelude VTEC (M4, 4.27 gears). This motor redlined at 7700 RPM, and being a smallish (2.2 litre I4) engine, it was kinda flat until the VTEC kicked at 4800 RPM, but from there to about 7600 RPM, it would scream, and the power only fell between 7600 and the rev limiter at 7700 or so. Also, no bashing on this car, it may not have been a Vette, but it was quick and handled VERY well. I had it for 173k miles with zero issues beyond basic maintenance.

See? Each engine works best with a gear that is matched to the engines power band. Too much gear, and you run out... it's that simple.

I hope this helps explain things a little clearer.

 

My late 86 had 2.59s, my 87 has 3.07s. I prefer the 2.59s, because the car never wants to hook up with the 3.07s. The 2.59 car hooked half the time.

 

Hooked?

 

With 3.07,I would do the intake/exhaust,1.6 RR and worry about the gears later.