Gear ratio question ???

[houston_t]

It A L L depends on what you want to do and get out of the car. Do you have a Grand National? They are mid 3 gearing with transmission ratios very similar to your 4L60E.
I see alot o f3.73 suggestions but that is pretty low for a tiny rear tire. The 1st gear ratio is 3:1, multiply that by 3.73 and consider the 14" white wall tire and there is zero chance you will be able to take advantage of that ratio during full throttle launch. So personally I do not see the need for a low rear gear.
Get a low 3's ratio to suit the car.

What are you getting from Quick Performance?

Seriously just a cruiser may do a little light to light action with my friends but nothing crazy, car will NEVER see the drag strip. It will see some highway use since I daily drive it when the weather is nice out. Sold my GN last year but yes the factory rear did well although I never ran the factory tire size for long I went with aftermarket wheels and tires. I had 19x9.5’s in the rear but don’t recall the tire size maybe a 285/35/19

Here is what I was looking at from quick performance.

 

[houston_t]

The 14" tire isn't much difference in circumfrence than a 15" tire on a stock G-body. Width may be a tad different. Once you start having some fun and tear off the 14" tires with 3.73, you'll get fatter ones. Trust me.

Working on getting another turbo Buick for that.

 

[Texas82GP]

So I have a 79 Monte that I just LS swapped. Car was an all original 35k mile car with the 4.4 and 3 speed trans, for the swap I went with a 2002 ls1 and 4l60e setup out of a trans am. Now that I have been driving the car I’m noticing I can get the rpm’s above say 3200 (unless I’m in neutral or park) I guessing the factory rear gear is the problem since I have a OD trans now. Has always been my plan to change out the carrier for a posi and new gear ratio, I’m trying to figure out what would be a good gear ratio to go with. Car will be a cruiser and will see highway time also I ride on 205/75/14 tires and don’t see myself changing that out anytime soon I want to keep the original look of the car. I plan on going with a setup from quick performance what would your suggestion be for a gear ratio ? Stock LS1 and stock converter with tire size listed earlier.

Thanks !

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I vote for a 3.42 for a fun cruiser. Here's why:

Tire height calculator - This is one of many. It's the one I like.

Tire Height Calculator - Wallace Racing

Tire Height Calculator by Wallace Racing

www.wallaceracing.com

Your tire height is 26.11"

The first gear ratio in the 4L60E is 3.059. 3.059 (first gear ratio) x 3.42 (rear ratio) = 10.46:1 final drive ratio in first gear. I wouldn't go any steeper than that. To put that into perspective, my truck has a 4L80E, which has a 2.48:1 first gear, the truck has a 4.10 rear gear and 32" tires. 2.48 x 4.10 = 10.17. The 10.46:1 you'd have with your 4L60E and a 3.42 will be plenty steep to get her off the line with good responsiveness. If you get onto it, traction will be a problem. With a 3.73 it's going to want to either spin the tires or jump right out of first gear before you can get across an intersection.

Lets look at 3.059 x 3.23 = 9.88. I like that better. Now let's look at Highway RPM for either a 3.42 or a 3.23

RPM Calculator - I like this one. Use the bottom section.

Engine RPM Calculator

The 4L60E has an overdrive ratio of 0.696:1. With your 26.11" tall tire, with a 3.42 rear axle, it will turn about 1991 RPM at 65 MPH and will turn about 2604 RPM at 85 MPH. This is a good range. At 45 MPH (about when it is going to want to shift into overdrive with a stock tune), it will be turning about 1378 RPM. This is fine.

With a 3.23, it should turn about 1302 RPM at 45 MPH, 1880 RPM at 65 MPH and 2459 RPM at 85.

I think either gear would be a good choice. I still vote for the 3.42. My guess is that's the gear set the Trans Am had in it. Hope this helps.

 

[Rt Jam]

The 14" tire isn't much difference in circumfrence than a 15" tire on a stock G-body. Width may be a tad different. Once you start having some fun and tear off the 14" tires with 3.73, you'll get fatter ones. Trust me.

Most of the thought on the reply was based on the traction available from a 205 whitewall. It pretty much sums up the fact launching with a deep gear is not the priority.

Houston has replied back with it being a highway cruiser. A low 3 rear combined with the 3:1 first will be plenty of off the line performance and the overdrive will be comfortable and efficient.

 

[L05edSS]

So I have a 79 Monte that I just LS swapped. Car was an all original 35k mile car with the 4.4 and 3 speed trans, for the swap I went with a 2002 ls1 and 4l60e setup out of a trans am. Now that I have been driving the car I’m noticing I can get the rpm’s above say 3200 (unless I’m in neutral or park) I guessing the factory rear gear is the problem since I have a OD trans now. Has always been my plan to change out the carrier for a posi and new gear ratio, I’m trying to figure out what would be a good gear ratio to go with. Car will be a cruiser and will see highway time also I ride on 205/75/14 tires and don’t see myself changing that out anytime soon I want to keep the original look of the car. I plan on going with a setup from quick performance what would your suggestion be for a gear ratio ? Stock LS1 and stock converter with tire size listed earlier.

Thanks !

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i'm with everyone else 3.73s nothing more or less. the SS came stock with them 85'-88 in my last ss put in a GN rear with the 3.42s and hated it.

 

[houston_t]

i'm with everyone else 3.73s nothing more or less. the SS came stock with them 85'-88 in my last ss put in a GN rear with the 3.42s and hated it.

What did you hate about the 3.42 ? Is there that much of a difference, 3.55 is also an option does anyone run that gear I don’t hear it mentioned often if ever.

 

[Texas82GP]

A stock 305 needed the 3.73. An LS1 doesn't.

 

[L05edSS]

What did you hate about the 3.42 ? Is there that much of a difference, 3.55 is also an option does anyone run that gear I don’t hear it mentioned often if ever.

1st it's the way i drive (too long to explain) but didn't like the RPM drop while cruising backroads and the other thing the trans i had rebuilt used to be albe to chirp OD and that ended when went with 3.42s. there were a few other things too. its preference stuff.

 

[69hurstolds]

My ZL1 is LS based with 3.73 standard. A n easy cruise on the highway in 6th. LS engines do just fine with 3.73 and OD. My opinion still is valid.

 

[403Olds]

My wife's GP with 305 and an OD has the 3.42. It's a decent compromise, but without the OD, the RPM's are almost 3K at 60 mph.