Anyone changed gears?
- Thread starter ShuggsRR
- Start date
'JustDreamin'
Dream: 6LV8 Turbo Bravada
Re: Anyone changed gears?
I know some guys have gone the other way (I believe Ed Hess is running 3.08's).
Personally, I'm thinking about changing gears in my Bravada from 3.73's to 3.08's, but I'll also be going from stock tire size (29" od) to 275 / 40 / 18's (26.7" od). And I'm running the 80E which only has a .75:1 overdrive (vs the .67 of the 700R4 / 60E). I'd love to change to 3.23's (which is offered for the 10-bolt) but I don't think its available for the 7.25" IFS front diff. Which means my choices are 3.42's or 3.08's.
Reason I'm thinking about changing gears is my cruise rpm is higher than I want. At 70 or so, I'm spinning like 2300rpm. And that's with the 29" tall tire. 3.42's would basically get me the same cruise rpm with the shorter tire.
'JustDreamin'
I know some guys have gone the other way (I believe Ed Hess is running 3.08's).
Personally, I'm thinking about changing gears in my Bravada from 3.73's to 3.08's, but I'll also be going from stock tire size (29" od) to 275 / 40 / 18's (26.7" od). And I'm running the 80E which only has a .75:1 overdrive (vs the .67 of the 700R4 / 60E). I'd love to change to 3.23's (which is offered for the 10-bolt) but I don't think its available for the 7.25" IFS front diff. Which means my choices are 3.42's or 3.08's.
Reason I'm thinking about changing gears is my cruise rpm is higher than I want. At 70 or so, I'm spinning like 2300rpm. And that's with the 29" tall tire. 3.42's would basically get me the same cruise rpm with the shorter tire.
'JustDreamin'
big gear head
axle builder
Re: Anyone changed gears?
I've changed 2 of them over to 3.08 gears. The differential case in the 7.2 IFS has to be changed to the 2 series. The 3.08 is the only gear that uses this differential case. The rear end is the same if you are still using the 7.5 10 bolt. The 3.42 uses a 3 series and the 3.08 uses a 2 series. If you go with the 3.73 then you won't have to change either one.
I've changed 2 of them over to 3.08 gears. The differential case in the 7.2 IFS has to be changed to the 2 series. The 3.08 is the only gear that uses this differential case. The rear end is the same if you are still using the 7.5 10 bolt. The 3.42 uses a 3 series and the 3.08 uses a 2 series. If you go with the 3.73 then you won't have to change either one.
jjorgensen52
NHSTE - I'm the only one!
Re: Anyone changed gears?
Gear Ratios... Rear................. 4th
.......................... 3.73............... 0.67
Tire Size... 26.5
RPM.... MPH 4th
600 ..... 18.93
700 ..... 22.08
800 ..... 25.24
900 .... . 28.39
1000.... 31.55
1100 .... 34.70
1200 .... 37.86
1300 .... 41.01
1400 ....44.16
1500 .... 47.32
1600 .... 50.47
1700 .... 53.63
1800 .... 56.78
1900 .... 59.94
2000 .... 63.09
2100 .... 66.25
2200 .... 69.40
2300 .... 72.56
2400 .... 75.71
2500 .... 78.87
2600 .... 82.02
2700 .... 85.17
2800 .... 88.33
2900 .... 91.48
3000 .... 94.64
3100 .... 97.79
3200.... 100.95
3300 ....104.10
3400 .... 107.26
3500 .... 110.41
3600 .... 113.57
3700.... 116.72
3800 ....119.88
3900 .... 123.03
4000 .... 126.19
4100 .... 129.34
4200 .... 132.49
4300 .... 135.65
4400 .... 138.80
4500 .... 141.96
4600 .... 145.11
4700 .... 148.27
4800 .... 151.42
4900 .... 154.58
5000 .... 157.73
5100 .... 160.89
5200 .... 164.04
5300 .... 167.20
5400 .... 170.35
5500.... 173.50
5600.... 176.66
5700.... 179.81
5800.... 182.97
My T-5 is better ... my motor is only going to be turning 1750 at 65mph :tup:
Gear Ratios... Rear................. 4th
.......................... 3.73............... 0.67
Tire Size... 26.5
RPM.... MPH 4th
600 ..... 18.93
700 ..... 22.08
800 ..... 25.24
900 .... . 28.39
1000.... 31.55
1100 .... 34.70
1200 .... 37.86
1300 .... 41.01
1400 ....44.16
1500 .... 47.32
1600 .... 50.47
1700 .... 53.63
1800 .... 56.78
1900 .... 59.94
2000 .... 63.09
2100 .... 66.25
2200 .... 69.40
2300 .... 72.56
2400 .... 75.71
2500 .... 78.87
2600 .... 82.02
2700 .... 85.17
2800 .... 88.33
2900 .... 91.48
3000 .... 94.64
3100 .... 97.79
3200.... 100.95
3300 ....104.10
3400 .... 107.26
3500 .... 110.41
3600 .... 113.57
3700.... 116.72
3800 ....119.88
3900 .... 123.03
4000 .... 126.19
4100 .... 129.34
4200 .... 132.49
4300 .... 135.65
4400 .... 138.80
4500 .... 141.96
4600 .... 145.11
4700 .... 148.27
4800 .... 151.42
4900 .... 154.58
5000 .... 157.73
5100 .... 160.89
5200 .... 164.04
5300 .... 167.20
5400 .... 170.35
5500.... 173.50
5600.... 176.66
5700.... 179.81
5800.... 182.97
My T-5 is better ... my motor is only going to be turning 1750 at 65mph :tup:
'JustDreamin'
Dream: 6LV8 Turbo Bravada
Re: Anyone changed gears?
I'm not sure I'd say that you'd have no highway cruising, just might spin a bit higher than you'd like. Does depend alot upon your tire diameter, if you're running a short tire, like 275 / 35's on 17's, then you may be spinning close to 3k at 75mph.....
From what I understand, the easiest (and probably least expensive) way to get a re-geared front diff is to buy another unit. I've looked around, and the salvage yards don't want all that much for them. Probably can score a good one for $200 to $250, which isn't that much more than a new gearset, and you don't have to set it up, which I understand is quite difficult.
'JustDreamin'
ShuggsRR said:
I'm not sure I'd say that you'd have no highway cruising, just might spin a bit higher than you'd like. Does depend alot upon your tire diameter, if you're running a short tire, like 275 / 35's on 17's, then you may be spinning close to 3k at 75mph.....
From what I understand, the easiest (and probably least expensive) way to get a re-geared front diff is to buy another unit. I've looked around, and the salvage yards don't want all that much for them. Probably can score a good one for $200 to $250, which isn't that much more than a new gearset, and you don't have to set it up, which I understand is quite difficult.
'JustDreamin'
mattw
Active member
Re: Anyone changed gears?
There is a u-pull-it yard near me that lets you have them for ~$50..
http://www.wegotused.com/
-Matt
There is a u-pull-it yard near me that lets you have them for ~$50..
http://www.wegotused.com/
-Matt
jjorgensen52
NHSTE - I'm the only one!
Re: Anyone changed gears?
Figured since the question got asked, I'd post the spreadsheetI used to create that listing of speeds. It can handle up to 6 gears.
All you do is plug in the diff ratio, individual gear ratios in the tranny, and tire size
Outputs tire height in inches, and speed in MPH for every 100 RPM increment from 600 to 5800 RPM
Download here
Figured since the question got asked, I'd post the spreadsheetI used to create that listing of speeds. It can handle up to 6 gears.
All you do is plug in the diff ratio, individual gear ratios in the tranny, and tire size
Outputs tire height in inches, and speed in MPH for every 100 RPM increment from 600 to 5800 RPM
Download here
Re: Anyone changed gears?
for the record the OD ratio in the 700R4/4L60E is a .70
Well alot of the buick guys have experimented with diff gears, and found the stock 3.42 to be about the best for an overall driver type car setup, but alot of hardcore racers switched to 3.23 or 3.08 because it loads the turbo more coming out of the hole and helps build boost faster, which makes everything better.
A turbo car likes the engine load to be higher, and this woudl be opposite if you went with 3.73, but with an NA LT1,m id def go with 3.73. I have them in my bravada and its a big differance over 3.42.
for the record the OD ratio in the 700R4/4L60E is a .70
Well alot of the buick guys have experimented with diff gears, and found the stock 3.42 to be about the best for an overall driver type car setup, but alot of hardcore racers switched to 3.23 or 3.08 because it loads the turbo more coming out of the hole and helps build boost faster, which makes everything better.
A turbo car likes the engine load to be higher, and this woudl be opposite if you went with 3.73, but with an NA LT1,m id def go with 3.73. I have them in my bravada and its a big differance over 3.42.
'JustDreamin'
Dream: 6LV8 Turbo Bravada
Re: Anyone changed gears?
For some reason .67 stuck in my mind, but its not correct. Granted, its only off by 2.6%, but it's off none-the-less.
Shruggs.....I'd suggest you find a good gear ratio calculator (there's a bunch online) and play with various ratios until you have a warm fuzzy feeling. You'll need to determine your tire size (if you haven't picked one yet) because that'll have a not insignificant impact. I'd suggest you look at all the gears, too. Compare road speed to rpm in 1st gear and 2nd. 3.06 is a pretty deep 1st gear, may be more than you want (not that it's easily changed or anything). Might even want to look at the rpm drop between 1st, 2nd, and 3rd (just to see how big a drop in rpm is. Then you've got to factor in how tight your converter is or isn't to see how it'll respond on the street. Awful lot of things to consider....
'JustDreamin'
Yeah, you're right, its .696:1. And 1st gear is 3.059, 2nd is 1.625, 3rd is 1:1HotRodV6 said:
For some reason .67 stuck in my mind, but its not correct. Granted, its only off by 2.6%, but it's off none-the-less.
Shruggs.....I'd suggest you find a good gear ratio calculator (there's a bunch online) and play with various ratios until you have a warm fuzzy feeling. You'll need to determine your tire size (if you haven't picked one yet) because that'll have a not insignificant impact. I'd suggest you look at all the gears, too. Compare road speed to rpm in 1st gear and 2nd. 3.06 is a pretty deep 1st gear, may be more than you want (not that it's easily changed or anything). Might even want to look at the rpm drop between 1st, 2nd, and 3rd (just to see how big a drop in rpm is. Then you've got to factor in how tight your converter is or isn't to see how it'll respond on the street. Awful lot of things to consider....
'JustDreamin'
'JustDreamin'
Dream: 6LV8 Turbo Bravada
Re: Anyone changed gears?
Completely off topic:
Hey HotRodV6, did you ever figure out the Envoy cladding for your Bravada?
'JustDreamin'
Completely off topic:
Hey HotRodV6, did you ever figure out the Envoy cladding for your Bravada?
'JustDreamin'
jjorgensen52
NHSTE - I'm the only one!
'JustDreamin'
Dream: 6LV8 Turbo Bravada
Re: Anyone changed gears?
Just to be nosey, what tire did you pic (since there are a bunch)? What wheels are you running? I'm leaning towards the Kumho ECSTA ASX myself, on 18" C5 wagons.
'JustDreamin'
That's the tire size I'm planning on running on my Bravada. OD is 26.7" or 778 revolutions per mile.ShuggsRR said:
Just to be nosey, what tire did you pic (since there are a bunch)? What wheels are you running? I'm leaning towards the Kumho ECSTA ASX myself, on 18" C5 wagons.
'JustDreamin'
'JustDreamin'
Dream: 6LV8 Turbo Bravada
Re: Anyone changed gears?
Sorry, this borders on hijacking your thread....
'JustDreamin'
Cool....Need any spacers?ShuggsRR said:
Sorry, this borders on hijacking your thread....
'JustDreamin'
'JustDreamin'
Dream: 6LV8 Turbo Bravada
Re: Anyone changed gears?
'JustDreamin'
I don't think I put that right. What I wanted to know is did you use any spacers???ShuggsRR said:
'JustDreamin'
'JustDreamin'
Dream: 6LV8 Turbo Bravada
Re: Anyone changed gears?
Ok, that's what I was looking for, because I haven't test fit the rims on my Bravada yet so see how they fit / look (and they don't have tires on them as yet, so it'll only help a little bit to throw the rim on it.).
'JustDreamin'
Ok, that's what I was looking for, because I haven't test fit the rims on my Bravada yet so see how they fit / look (and they don't have tires on them as yet, so it'll only help a little bit to throw the rim on it.).
'JustDreamin'