cruising rpm with 3.73's?
12-28-2010, 09:25 PM
#1
Staging Lane
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cruising rpm with 3.73's?
ok, im pretty sure my truck has factory 3.73 with the g80, however it seems to run pretty high rpms at 70mph. its got 265/70 tires on it and im cruising around 23-2400 rpm. my old truck with 275/55/20 tires and 4.10 cruised at that or a lil lower. im pretty sure the two tires are REAL close in height, so shouldnt i be turning fewer rpms?? the reason im wondering is my highway fuel mileage is TERRIBLE for a 5.3 1/2 ton averaging 13.5mpg. i was thinking more like 17-18 at the least is normal. any input appreciated thanks!
12-28-2010, 09:38 PM
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I'd say they are the same gears.
The 275/55/20 are 31.9 inches tall
265/70/17 are 31.6 inches tall
Either you have 4.10s in your truck or something else is wrong...
The 275/55/20 are 31.9 inches tall
265/70/17 are 31.6 inches tall
Either you have 4.10s in your truck or something else is wrong...
12-28-2010, 09:56 PM
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sounds to me like your torque converter isn't locking up in OD.
also in cold climates, it takes longer for it to lockup because a set of temperature parameters has to be met.
also in cold climates, it takes longer for it to lockup because a set of temperature parameters has to be met.
12-28-2010, 10:00 PM
#4
You left out the wheel size to calculate from or at least I didn’t see it, but assuming you had a 265/70/16, you should be turning around 2000rpm at 70mph. If you have 265/70/17’s, you would be looking at around 1958rpm at 70mph.
To be turning that kind of rpm, I believe the clutch in your torque converter is not locking up. With a 30.6” tire that would put you turning about 2350rpm at 70mph, while with a 31.6” tire that would put you turning about 2273rpm at 70mph, which is similar to the speeds you’re describing.
To be turning that kind of rpm, I believe the clutch in your torque converter is not locking up. With a 30.6” tire that would put you turning about 2350rpm at 70mph, while with a 31.6” tire that would put you turning about 2273rpm at 70mph, which is similar to the speeds you’re describing.
12-29-2010, 06:56 AM
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Staging Lane
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thanks you guys have all assures me im not outa my mind i guess ill start by pulling the cover and counting teeth, if it is indeed a 4.10 then looks like a set of 285's are in my near future otherwise ill be pickjng up a tb coverter been wabting one anyways
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12-29-2010, 10:31 AM
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assuming it hasnt been changed but as far as i know gm never offered anything over a 3.73 in a 1/2 ton 4x4 in 05 edit: i just noticed ur codes didnt know 4.10 wad an option thanks