4xcrazy
3/4 ton status
I guess I should correct my post, if you guys are referring to 3.42 gears in a 14bff... mine was a factory 10 bolt with those gears... 
CK5
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RPMs at 65mph?
- Thread starter whitezracer
- Start date
I've seen a set of 3:23 axles for an 80's 3/4 ton for sale on Craigslist locally not long ago,but the 14 bolt was a semi-floater...not an FF..
They had 3:42's in 3/4 tons in the 80's also,they were not that common though,neither were 3:23's ,the few I saw were in diesel pickups like my '82 GMC K2500 (which I think possibly has 3:23's or 3:42's in it,never confirmed it yet)..also 2WD trucks had those ratios more often,4x4's seem to have 3:73's or 4:10's factory more than any of the other available ratio choices..
I dont know if 1 tons had 3:23's or 3:42's available or not..I've seen 6:17's in a few dually P series step vans though...
They had 3:42's in 3/4 tons in the 80's also,they were not that common though,neither were 3:23's ,the few I saw were in diesel pickups like my '82 GMC K2500 (which I think possibly has 3:23's or 3:42's in it,never confirmed it yet)..also 2WD trucks had those ratios more often,4x4's seem to have 3:73's or 4:10's factory more than any of the other available ratio choices..
I dont know if 1 tons had 3:23's or 3:42's available or not..I've seen 6:17's in a few dually P series step vans though...
Stomis
Professional Amateur
lol 2000rpms at 65mph? Thats a really low. I would shoot for at least 2300ish. In all honesty just go to 5.13s. The slight loss of highway MPG from picking up a 100rpms at cruise will more than be made up for by what you'll pick up around town with your truck not struggling to get moving.
y5mgisi
1 ton status
I don't know. I'm sure being on 35s and stuff makes a difference but my 12 with the double overdrive and 3.42s and I'm guessing 31's does like 1600 rpm at 65 I think.
4xcrazy
3/4 ton status
Back when I had the 3.42's running stock tires at 31/10.5-15's it ran pretty good and got decent fuel mileage for the size vehicle it is. It never seemed to hunt for gears much really, sounded good in the rpm range and could do 65-75 decently without a struggling engine sound.
NOW, with the 4.10's and 35's I really don't like going much over 65-70, and it will definitely hunt between overdrive and 3rd gear on the slightest hills if you let it. The engine sounds like it's lugging a lot and when I can get it up to a normal sounding range, trying to run say 75ish, it just seems to be a struggle to keep it at that speed. I'm guessing it has something to do with the aerodynamics of a brick thing though.
I know mine isn't geared right, I don't race it or try to get it going in a hurry at all, just drive it easy, and reasonable on the freeway.
Of course now, living in Washington, the freeway speed limits for the most part are mostly 60mph, some areas at 65, so I'm not gonna be bugged too much about it.
NOW, with the 4.10's and 35's I really don't like going much over 65-70, and it will definitely hunt between overdrive and 3rd gear on the slightest hills if you let it. The engine sounds like it's lugging a lot and when I can get it up to a normal sounding range, trying to run say 75ish, it just seems to be a struggle to keep it at that speed. I'm guessing it has something to do with the aerodynamics of a brick thing though.
I know mine isn't geared right, I don't race it or try to get it going in a hurry at all, just drive it easy, and reasonable on the freeway.
Of course now, living in Washington, the freeway speed limits for the most part are mostly 60mph, some areas at 65, so I'm not gonna be bugged too much about it.
Stomis
Professional Amateur
Yeah but dude thats a what 340ish HP gen 5 vs an old 305/350?
MrSchaeferPants
1/2 ton status
This is a chart we should all be familiar with. But back to the OP.
Now, of course the chart represents a 1:1 transmission ratio, but we're talking 700r4 per the OP. As you see the 'close to factory' ratio for a 35" tire is approx 4.56. In OD with the 700r4 and a .70 4th gear, you'll be happy with a few more RPMs, that's why 5.13s are great for the combo. Hunting trans is a mixture of things, more RPMs in a round about way tends to be one way of "fixing it", while simultaneously giving you low gear fun power. You can safely be on the 'more power' side of the lower gears with OD.
It's a heavy rig, with the aerodynamics of a brick, with big tires. It WANTS low gears.
The major factor is the tire diameter. Your muscle cars can be plenty happy with 3.73/4.10 because they still have regular sized tires. In a sense, you have to overcompensate gear ratio due to the larger diameter tire. Nor do you need to be in 'better gas mileage' range, because that's handled by OD (once again, the chart represents a 1:1 tranny). It'd be a different story if you had a th350, 400 or sm465. Now add 65mph with a lifted brick with big tires, and you could really use those lower gears, especially when it comes to hills.
So you're not lowering gears to add power, you're lowering gears to correct back to factory (if you choose)
Now, of course the chart represents a 1:1 transmission ratio, but we're talking 700r4 per the OP. As you see the 'close to factory' ratio for a 35" tire is approx 4.56. In OD with the 700r4 and a .70 4th gear, you'll be happy with a few more RPMs, that's why 5.13s are great for the combo. Hunting trans is a mixture of things, more RPMs in a round about way tends to be one way of "fixing it", while simultaneously giving you low gear fun power. You can safely be on the 'more power' side of the lower gears with OD.
It's a heavy rig, with the aerodynamics of a brick, with big tires. It WANTS low gears.
The major factor is the tire diameter. Your muscle cars can be plenty happy with 3.73/4.10 because they still have regular sized tires. In a sense, you have to overcompensate gear ratio due to the larger diameter tire. Nor do you need to be in 'better gas mileage' range, because that's handled by OD (once again, the chart represents a 1:1 tranny). It'd be a different story if you had a th350, 400 or sm465. Now add 65mph with a lifted brick with big tires, and you could really use those lower gears, especially when it comes to hills.
So you're not lowering gears to add power, you're lowering gears to correct back to factory (if you choose)
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No kidding! The Diesel crowd would have loved you!
I searched through the classifieds for threads from that used, but didn't see 3.21 or 3.42 gear sets. But it prolly doesn't matter in the long run (unless he comes up with another set
).
runamok151
1 ton status
'89 K5, 5.7 tbi, 700r4, 4.56s and 35s. I'm right at 1850 at 65. I had to take a trip south right after I put the 35s on and didn't have time to regear. W/ the stock 3.73s, the truck wouldn't hold OD on a grade and even shifted down to 2nd gear of some of the hills on I-81 in S. VA. The trans doesn't hunt at all now w/ the 4.56s. I've since made the same drive in the K5 and it held OD on even the steepest grades.
If you plan to spend a lot of time off road or may go to 37s in the future, put 4.88s in.
If you plan to spend a lot of time off road or may go to 37s in the future, put 4.88s in.
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