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4.88 Gear Ratio Too Much with 37" tires?

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Dmacmilitant

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Hey Everyone,

Friend of mine has a 2016 2500 Ram Cummins SO with 68RFE trans with 37" tall tires. He has the stock gear ratio of 3.42 in that model.

I have a 2020 Ram 2500 Cummins with 3.73 and 37" tall tires, same transmission. I feel like mine pulls my trailer just fine and performs well with this setup.

He called Yukon and asked their opinion on what to swap his gear ratio over to from stock and they suggested 4.88 gears. He was bouncing this off me for my opinion and my initial thought is that is way too much of a change. We are using the Spicer online RPM calculator and it matches up with what Yukon said, which was the truck will be at about 2,220 RPM when going 80MPH down the road. All my research on this forum has shown me that the big decision is between 3.73 and 4.10. I feel his jump from 3.42 to 4.88 is just too large. Maybe whatever is inbetween 4.10 and 4.88 would be better.

His ultimate goal here is to get some of his torque and pull back to be like where he was at stock. He pulls a 12,000lb 5th wheel at most and would like some of that towing pull back as well.

All feedback is highly welcomed and much appreciated!
 
For 37's 4.88 gearing will probably put the rpm range back where it should be. I'm running 4.88s in my Jeep with 33" tires. Much different vehicle but anything more than 60mph and the motor screams.

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Had a F250 with the V10 gas motor. Stock gears were 4.30. Truck had larger tires than stock, 33s.
4.88 and 37s sounds about right.
 
Too much.

A 37" tire truly measures around 36.5" That tire with 4.88's at 75 mph with the 68rfe in 6th gear has you at 2123 rpm. MPG begins to suffer greatly on this motor after 2k rpm from what ive found.

If it were me, i'd do 4.10's with that tire which would put him at 1784 rpm at 75mph ... sweet spot IMO.

Diesels do not have the RPM range that a gas motor does (cummins is about done at 3k rpm) so that really needs to be considered when making a change.
 
If he wants the 2016 stock feel back. 3.73s with 37s will get him very close to the 3.43 ratio with stock tires. Having said that I would step up to 4.10s to protect the 68RFE a little more. IMO, 4.88 is too high for the Cummins with the usage you mentioned.
 
If you have a lot of highway driving, go with 4.10s. If you have a lot of off roading or heavy towing, go 4.88s. If you like a balance of both, got with 4.30s.
 
My PW has 4.10s. I love it on 33s. If I went to 37s it wouldnt be as much fun

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I went 1 step further at 5.13s on my 16 PW Hemi on 37s. I had zero regrets of not doing 4.88 with the gasser. A tiny bit buzzy, but fine. 4.88 seems excessive for a diesel. 4.56 would be interesting math.

Edit to add: in my experience, a single step change never pencils out to be worth it, and way more true with the diesel torque. 3.42 to 3.73 is silly. 3.73 to 4.10 is silly etc.
 
jkbrereton said:
My PW has 4.10s. I love it on 33s. If I went to 37s it wouldnt be as much fun

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Click to expand...

Your PW has half the torque as the OP. Not apples to apples.


RPS1030 said:
I went 1 step further at 5.13s on my 16 PW Hemi on 37s. I had zero regrets of not doing 4.88 with the gasser. A tiny bit buzzy, but fine. 4.88 seems excessive for a diesel. 4.56 would be interesting math.

Edit to add: in my experience, a single step change never pencils out to be worth it, and way more true with the diesel torque. 3.42 to 3.73 is silly. 3.73 to 4.10 is silly etc.
Click to expand...

Again, this is not about a gas truck. Truck is a diesel. Nowhere near comparable.
 
gimmie11s said:
Your PW has half the torque as the OP. Not apples to apples.




Again, this is not about a gas truck. Truck is a diesel. Nowhere near comparable.
Click to expand...
Thanks for the input on your first reply and I'm in agreement. I've relayed the info to my buddy and everyone's input is appreciated.
 
I am beginning to question if I should go with 4.10's instead of the 4.44's I am planning on doing. I have 37'' Toyo MT's and even if I ever switch it will be still 37''. I am going to be annoyed with the highway rpm with 4.44's? I am wondering if 4.10's would be enough to get out of lugging territory but also not to much to be excessive at all. Or, if 4.10 is just not that much different than the 3.73 in it now and I am better off going to 4.44's.
 
AEV_CUMMINS said:
I am beginning to question if I should go with 4.10's instead of the 4.44's I am planning on doing. I have 37'' Toyo MT's and even if I ever switch it will be still 37''. I am going to be annoyed with the highway rpm with 4.44's? I am wondering if 4.10's would be enough to get out of lugging territory but also not to much to be excessive at all. Or, if 4.10 is just not that much different than the 3.73 in it now and I am better off going to 4.44's.
Click to expand...
4.10s will be more than enough gear for you…. I remember running 3.55s on 35s the old 12V 140hp pulling 10klbs struggled but held its own…. With the new diesels power i would stick with 3.73 and be perfectly happy
 
Ughhhh this is only getting more difficult lol. I am leaning towards just doing the 4.44's because of the extra leverage but also really appreciate the smooth and quiet highway ride. I got out of a gas truck because I prefer to stay lower in the rpm's and the smoothness. If the truck had a 8 speed I would have not one worry about doing 4.44's but there is something telling me that 4.44's will change the character of the truck more than I want. All I want is not to have to downshift manually going up a hill and be in boost at cruising more often. It seems like 4.10's would work just fine but I worry it would be a waste of money if it makes almost no difference.
 
AEV_CUMMINS said:
Bit the bullet and switched order to the 4.10’s. For my driving and goals I think it will be perfect. Just want a few hundred more rpm which this should do perfect. Couple weeks for them to come in then I will update!
Click to expand...
where did you order your stuff from
 
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