Rear End Gear Change (G80)
01-11-2004, 04:44 PM
#1
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Join Date: Oct 2003
Location: Carmel, California
Posts: 179
Rear End Gear Change (G80)
1st off, I was recently informed I have a G80 positive traction rear end. I want to know how easy it is to change gears in the rear end, I also want to know my ratio (G80) and a good gear ratio for good acceleration. How many bolts is the G80 rear? What is the difference between 3.08 and 5.57 gears? Also if I was to switch to a gear that gave me better acceleration how much of a difference could I/ would I notice? Thanks,
-Ville H. Valo
-Ville H. Valo
01-11-2004, 05:22 PM
#4
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Join Date: Mar 2001
Posts: 3,249
Originally posted by Ville H. Valo
i just want the car to accelerate more quickly. so if i got 5.38 it would be jummpy???? <=========bad gas mileage?
i just want the car to accelerate more quickly. so if i got 5.38 it would be jummpy???? <=========bad gas mileage?
I think 3.73s will be more than you need unless do have done something radical.
01-11-2004, 05:37 PM
#6
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Join Date: Mar 2001
Posts: 3,249
It would be too much. Your cam and gear needs to be matched. If your gear pulls your RPM range out of the abilities of the engine, you will not have good acceleration. 4.10s are marginal when it comes to a daily driver. Believe me, I have been there and done that and regretted it. Also, you will have to get a speedo gear fix in the tranny because there is no direct fit set of drive and driven gears where there is for the 3.73.
You could pay thru your *** for a GM set or get a Richmond Gear set for under $200. GM ones are, I believe, a little under $400. If you have to ask the question, you are not capable of doing it yourself. You will need a professional who has the tools and the ability to follow Richmond Gear's instructions to the letter. I had a mechanic try to use GM's instructions and the gears howled. To quieten it, you will have to follow their instructions to the letter. My tech who has been doing it for years had to take it in and out 4 times to get it just right. You have to adjust it according to their specs and there is where the fun begins. Now you have to take a wear patter test and if that isn't right, take it out and reshim till you get the pattern right. You need a dial indicator and know how to use it and some other special tools to make it easier.
After all is said and done, your speedo will be wrong and hence your VSS reading will be off. Now you have to take the tail of the tranny off and put in a custom drive gear on the shaft and put a custom driven gear on the vss. I believe LPE sells them for around $125 or so.
You could pay thru your *** for a GM set or get a Richmond Gear set for under $200. GM ones are, I believe, a little under $400. If you have to ask the question, you are not capable of doing it yourself. You will need a professional who has the tools and the ability to follow Richmond Gear's instructions to the letter. I had a mechanic try to use GM's instructions and the gears howled. To quieten it, you will have to follow their instructions to the letter. My tech who has been doing it for years had to take it in and out 4 times to get it just right. You have to adjust it according to their specs and there is where the fun begins. Now you have to take a wear patter test and if that isn't right, take it out and reshim till you get the pattern right. You need a dial indicator and know how to use it and some other special tools to make it easier.
After all is said and done, your speedo will be wrong and hence your VSS reading will be off. Now you have to take the tail of the tranny off and put in a custom drive gear on the shaft and put a custom driven gear on the vss. I believe LPE sells them for around $125 or so.
01-11-2004, 05:39 PM
#7
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Join Date: Mar 2001
Posts: 3,249
Originally posted by Ville H. Valo
i have a LB9, what is the gear ratio on a stock G80 rear end. would 4.10 be good? how hard is it to change?
i have a LB9, what is the gear ratio on a stock G80 rear end. would 4.10 be good? how hard is it to change?
01-11-2004, 05:39 PM
#8
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5.38 is an insane rear gear. I rarely see more than 5.13s even on drag only cars.
3.73s are a nice street gear. I prefer 3.55s if you have TPI, cause it produces plenty of torque down low so you dont need the extra gear to make up for it. Plus TPi dies at high RPMs anyway so you dont wanna ooutrun your powerband by overgearing it.
3.73s are a nice street gear. I prefer 3.55s if you have TPI, cause it produces plenty of torque down low so you dont need the extra gear to make up for it. Plus TPi dies at high RPMs anyway so you dont wanna ooutrun your powerband by overgearing it.
01-11-2004, 05:39 PM
#9
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Location: Mooresville, NC
Posts: 2,043
G80 isn't a rear gear code. Run your RPO's at www.thirdgen.org. Like aklim said, 3.73's 
That's what I've got (sitting in garage ready to go in). The higher the number (lower the gear) the faster acceleration and lower MPG. Vice versa.
-Corey
That's what I've got (sitting in garage ready to go in). The higher the number (lower the gear) the faster acceleration and lower MPG. Vice versa.-Corey
01-11-2004, 06:02 PM
#13
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Posts: 3,249
I wouldn't go past that for a LB9. 3.55 or 3.73 would be alright for the street. Of course, if you plan many more mods in the future like say changing the tranny to a 200R4 or a T56 where you have a super low overdrive, you might be able to get away with 4.10.