BenK
SF BayArea
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Twins4us07 wrote:Underdrive?
Look for 'under' or 'under drive' and read up.
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1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...
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smkettner
Southern California
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Carrier breaks are used to allow different diameter pinion gears that have more or less teeth to make the ratio. Different diameter pinions require the ring gear to be thicker or thinner to position it properly. Or a different carrier is used to change the position. Sometimes a thick or thin ring gear is available aftermarket where as the OEM gear might require the carrier change.
So they both might be right on needing a change or not because it depends on the gears set and how it is manufactured.
Read more here on carrier breaks: Randy's Ring & Pinion common carrier breaks
Randy's - Do I really need to buy another carrier?
Just keep in mind 3.73 to 4.56 will change your rpm 22% in every gear. So if you are running 3000 rpm you will be at 3660 with the change. Of course you might run lower RPM if you can use the next higher transmission gear. In general the gear change will be easier on the transmission for towing at the max and even using OD.
I went 3.55 to 4.10 and often wish I had gone 4.56. It should only be $1000 per axle max parts & labor. Plus a few hundred if you do need a carrier. It is an all day job.
I don't know GMC but my Ford needed a programer to change the computer to know it had 4.10.
BTW what size tire do you have?
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2001 F150 SuperCrew 5.4 Lariat Offroad 4x4 Tow Package 4.10 Truetrac
2006 Keystone Springdale 249FWBHLS
12K SuperGlide, KGE3000Ti 2.3kw rated 2.6kw max
Frank's voltage booster, Prosine 1800 powered by 4 GC2 batteries
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dragr1
Alabama
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mkirsch wrote:Going from 3.73 to 4.56 gears is about the same as running in 3rd instead of OD.
IIRC the OD ratio for the 700R4/4L60/4L60E is .7, and the ratio of 3.73 to 4.56 is .8.
So close, it's not worth the time or the money unless you're drag racing and need the torque off the line.
If the rumors are true, you don't want to tow heavy in OD with a 4L60-series transmission anyway, due to the rumored weak OD clutches.
Good point here, this is why I just tow in 3rd gear and save the extra $$ from not doing a gear change to buy gas with.
1991 Allegro M31 Basement
1985 4Runner Rockcrawler
2000 Suburban 2500 4x4
2007 Toyota Tacoma Crew Cab TRD 4x4
2002 Lexus IS300
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BillyW
North ID
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I don't know if this could be an issue for you or not. It was stressed to me when I went from 3.55 to 4.10 that passing the (Washington St.) emissions test would be more difficult as the engine would be running higher RPMs. Several shops wouldn't do it for just that reason. Since I live across the state line in Idaho, I have no emissions rules to worry about.
'97 F150 4X4
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dodge guy
Chicago, western subs.
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dragr1 wrote:mkirsch wrote:Going from 3.73 to 4.56 gears is about the same as running in 3rd instead of OD.
IIRC the OD ratio for the 700R4/4L60/4L60E is .7, and the ratio of 3.73 to 4.56 is .8.
So close, it's not worth the time or the money unless you're drag racing and need the torque off the line.
If the rumors are true, you don't want to tow heavy in OD with a 4L60-series transmission anyway, due to the rumored weak OD clutches.
Good point here, this is why I just tow in 3rd gear and save the extra $$ from not doing a gear change to buy gas with.
Unfortunately thats not how it works! a gear change can make between a 2-800 rpm difference. thats less than running in 3rd as apposed to O/D. you`de be amazed the difference a few hundred rpm can do for performance!
BillyW wrote:I don't know if this could be an issue for you or not. It was stressed to me when I went from 3.55 to 4.10 that passing the (Washington St.) emissions test would be more difficult as the engine would be running higher RPMs. Several shops wouldn't do it for just that reason. Since I live across the state line in Idaho, I have no emissions rules to worry about.
Gear ratios have nothing to do with emissions. if they did the manuf. wouldn`t offer the different ratios they do! the PCM programing in a vehicle with 3.55 gears is the same as a one with 4.30`s. the engine just operates at a different rpm.
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smkettner
Southern California
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BillyW wrote:I don't know if this could be an issue for you or not. It was stressed to me when I went from 3.55 to 4.10 that passing the (Washington St.) emissions test would be more difficult as the engine would be running higher RPMs. Several shops wouldn't do it for just that reason. Since I live across the state line in Idaho, I have no emissions rules to worry about.
CA has some of the toughest testing and we use a dynomometer during the test.
Mine passed with no issues with my 3.55 to 4.10 swap and reprogrammed computer.
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dodge guy
Chicago, western subs.
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smkettner wrote:BillyW wrote:I don't know if this could be an issue for you or not. It was stressed to me when I went from 3.55 to 4.10 that passing the (Washington St.) emissions test would be more difficult as the engine would be running higher RPMs. Several shops wouldn't do it for just that reason. Since I live across the state line in Idaho, I have no emissions rules to worry about.
CA has some of the toughest testing and we use a dynomometer during the test.
Mine passed with no issues with my 3.55 to 4.10 swap and reprogrammed computer.
Oh yeah! I forgot about the GM`s needing to have the programmer to change the speedo! add that edit to my previous post. however it still won`t change the emissions calibrations.
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dragr1
Alabama
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dodge guy wrote:dragr1 wrote:mkirsch wrote:Going from 3.73 to 4.56 gears is about the same as running in 3rd instead of OD.
IIRC the OD ratio for the 700R4/4L60/4L60E is .7, and the ratio of 3.73 to 4.56 is .8.
So close, it's not worth the time or the money unless you're drag racing and need the torque off the line.
If the rumors are true, you don't want to tow heavy in OD with a 4L60-series transmission anyway, due to the rumored weak OD clutches.
Good point here, this is why I just tow in 3rd gear and save the extra $$ from not doing a gear change to buy gas with.
Unfortunately thats not how it works! a gear change can make between a 2-800 rpm difference. thats less than running in 3rd as apposed to O/D. you`de be amazed the difference a few hundred rpm can do for performance!
BillyW wrote:I don't know if this could be an issue for you or not. It was stressed to me when I went from 3.55 to 4.10 that passing the (Washington St.) emissions test would be more difficult as the engine would be running higher RPMs. Several shops wouldn't do it for just that reason. Since I live across the state line in Idaho, I have no emissions rules to worry about.
Gear ratios have nothing to do with emissions. if they did the manuf. wouldn`t offer the different ratios they do! the PCM programing in a vehicle with 3.55 gears is the same as a one with 4.30`s. the engine just operates at a different rpm.
Well, 3rd gear is pretty close-at 70mph in 3rd I run about 2900 rpm, and if I switched to 4.56 and ran in overdrive it would be around 2700 rpm at 70mph. Yes I tow at 70mph sometimes-but I'm only towing an 18' car trailer with an offroad rig on it.
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Dave H M
IL
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Twins
Are you towing in or out of OD?
Wy back when I hd a gasser, I towed out of OD and as I recall usually ran around the 2600 rpm.
Maybe you have already given that info and it got lost in the dust.
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smkettner
Southern California
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dragr1 wrote:Well, 3rd gear is pretty close-at 70mph in 3rd I run about 2900 rpm, and if I switched to 4.56 and ran in overdrive it would be around 2700 rpm at 70mph.
As long as you are comfortable driving 70 mph unloaded in OD at 2700 rpm on a daily basis I say go for it.
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