Gear Swap....recommendations
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Elder User
Joined: Jun 2002
Posts: 812
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From: Woodbridge NJ
Gear Swap....recommendations
Hey Guys!
I'm thinking it's time to do a gear swap. I've saved up enough money for the install, and I'm gonna bit the bullet.
What ratio would you recommend? I'm currently running stock 3.73's w/ a limited slip in the rear. I noticed a big difference when I upgraded to 40" tires. Now it's time to get back to the stock feeling.
I'm thinking it's time to do a gear swap. I've saved up enough money for the install, and I'm gonna bit the bullet.
What ratio would you recommend? I'm currently running stock 3.73's w/ a limited slip in the rear. I noticed a big difference when I upgraded to 40" tires. Now it's time to get back to the stock feeling.
Freshman User
Joined: Jun 2009
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I'd first swap the Dana 50 for 60, then go for 5:13's. I swapped to the 60 and went 4:30's with 35" tires…I've got 250 or so more RPM's at 75 mph..which with 40's you can use the extra rpms to keep them rolling…a few more lbs of boost too to help keep the EGTs lower.
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Cargo Master
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From: chicago northwest suburbs
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Post Fiend
Joined: Aug 2010
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From: Manchester, CT
Yeah but its not a V10. Ive never heard of guys with diesels swapping much lower than 4.30s...i have 35s and 3.73s and its like perfect all around. Most people run 37s on 3.73s and have no issues
Super Moderator
Joined: May 2004
Posts: 29,380
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From: Central Coast of CA
A little higher than stock.
Don't get me wrong, I'm not knocking you, just trying to get a feel for how much experience you have with that combo, or close to that combo, because your experience may be that you won't be disappointed, but it's been my experience that people with too tall of a gear (numerically speaking) and not enough tire to offset it, will be disappointed.
My fellow moderator Toreador Diesel followed peoples advice for R&P ratio and he regretted it because the gear was too much, even though everyone told him the gear ratio calculator said he would be spot-on equivalent with the stock ratio.
He had to do a second R&P gear swap (very expensive) because he went with the "general consensus."
In my opinion, you would be very pleased with 4.56 gears. The 4.88's would be too much, in my opinion.
Stewart
Last edited by Stewart_H; Apr 19, 2014 at 08:30 PM.
Senior User
Joined: Sep 2013
Posts: 224
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From: Central Valley
That is close, but the 4.88's would push him to the high end of usable RPM's.
My fellow moderator Toreador Diesel followed peoples advice for R&P ratio and he regretted it because the gear was too much, even though everyone told him the gear ratio calculator said he would be spot-on equivalent with the stock ratio.
He had to do a second R&P gear swap (very expensive) because he went with the "general consensus."
I think Tor's example was 4.30 gear for 35" tires. He overshot by ~4.88%
going with 4.30 instead of 4.10. He should have gone with 4.10 in the first place.
Miles has the right idea. I have a 6" lift with 4.30's on 37" tires and I'm like 0.5 mph off on my speedo.
This is because 37" tire calls for 4.36 ratio "mathematically." 4.3 is perfect.
4.36/4.3=1.01395 (~1.4% off)
1.01395x70mph= 70.977 (~0.98mph off)
In my opinion, you would be very pleased with 4.56 gears. The 4.88's would be too much, in my opinion.
He'll be happier with 4.71
Stewart
My fellow moderator Toreador Diesel followed peoples advice for R&P ratio and he regretted it because the gear was too much, even though everyone told him the gear ratio calculator said he would be spot-on equivalent with the stock ratio.
He had to do a second R&P gear swap (very expensive) because he went with the "general consensus."
I think Tor's example was 4.30 gear for 35" tires. He overshot by ~4.88%
going with 4.30 instead of 4.10. He should have gone with 4.10 in the first place.Miles has the right idea. I have a 6" lift with 4.30's on 37" tires and I'm like 0.5 mph off on my speedo.
This is because 37" tire calls for 4.36 ratio "mathematically." 4.3 is perfect.
4.36/4.3=1.01395 (~1.4% off)
1.01395x70mph= 70.977 (~0.98mph off)
In my opinion, you would be very pleased with 4.56 gears. The 4.88's would be too much, in my opinion.
He'll be happier with 4.71
Stewart
1.0361x70mph=72.53mph (~2.53mph off)
4.56 instead of 4.71 is ~3.33% off (4.71/4.56=1.0329)
1.0329x70mph=72.30mph (~2.3mph off)
OP's ratio of 4.71 is not available so either 4.56 or 4.88
4.56 if the truck is running around empty.
4.88 if the truck is going to tow heavy.
Also, going from stock tires to 35" isn't that big of a difference. Going from stock tires to 40" is a huge difference. Not only weight, but also width.With 4.88 gears, you overshoot ~3.61% which shouldn't be too bad when you factor in the big,wide and heavy tires into the equation. (I'm talking about towing)