Buddy of mine just took delivery of his '08 LMM Dually and immediately put 22.5" Big Rig Tires/Wheels on it. He considering going with 4:56 gears to bring back torque to where it should be. Is there a downside to doing this? Will it bring the speedo back (close) to where it should be?
-
Welcome to The Truck Stop! We see you haven't REGISTERED yet.
Your truck knowledge is missing!
- Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
- We have tons of knowledge here for your diesel truck!
- Post your own topics and reply to existing threads to help others out!
- NO ADS! The site is fully functional and ad free!
Problems registering? Click here to contact us!
Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!
4:56 Gears?
- Thread starter rcpd34
- Start date
just a number
Active Member
what gears were in there to start with? and what size of tires, before and after?
just a number
Active Member
it would be close, but I need the tire sizes to figure out the exact difference.
4.56 vs. 3.73 86% difference in tire speed.
255/70R22.5(563 rev per mile) vs.255/75r17(652 rev per mile) 1.15% difference in miles per rev. 4% overall. 60mph=57.6mph
hope that's the info you were looking for.
1 more thing to know (per tire)
255/70R22.5=95lbs
255/75r17=43lbs.
4.56 vs. 3.73 86% difference in tire speed.
255/70R22.5(563 rev per mile) vs.255/75r17(652 rev per mile) 1.15% difference in miles per rev. 4% overall. 60mph=57.6mph
hope that's the info you were looking for.
1 more thing to know (per tire)
255/70R22.5=95lbs
255/75r17=43lbs.
Heartbeat Hauler
A(ACLU) Agent Yoda
I don't know if I would do a gear change for that. I might have a pro build a tow tune (modest power increase like 50 or 60 hp) and just have the new tire size programmed in and leave the gears as they are. This would insure all your readings, speedo, abs, etc. were all on the same page and no funky drivability issues, plus with the extra ponies which would include additional torque you could still pull anything you wanted. I bet it would be cheaper too. That's my $.02 worth. :thumbsup:
JP
JP
Last edited:
stacks04
McLovin
is it 4wd? ton of money in parts and labor to make the change. like heartbeat hauler said a tune would be cheapest and best bang/buck.
He currently has the Edge EVO tuner. If he really wants it, money won't be an issue. Here is a link to a similar thread I started on DP. It has a neat gear calculator someone made in Excel.
http://www.dieselplace.com/forum/showthread.php?t=252115
Works pretty cool.
http://www.dieselplace.com/forum/showthread.php?t=252115
Works pretty cool.
Heartbeat Hauler
A(ACLU) Agent Yoda
That's cool that his cup runneth over with cash, but what is he gaining by going to 4.56 gears when he doesn't have to?
JP
12ga diesel
Jack of all, Master of none
I'd say go with the nice tow tune of 50-60 hp and keep the gears what they are. If doing that, there would be no real advantage to changing the gears.
Heartbeat Hauler
A(ACLU) Agent Yoda
No. By adding the tune you are able to program the computer for the larger tires which addresses all the issues with the speedo, ABS, tach, etc. No need for the gears. Like we said before.
JP
Matt Bachand
Depends on the 6.5
I can't see how 4.56 would bring his MPG back up.
I dont' think you would ever want a 4.56 gear unless your Hauling tremedous weight... 4.11 maybe... but most desire 3.73 I guess it depends on what he uses the truck for.
Ragindiesel
New Member
- Messages
- 258
- Reaction score
- 0
likey with oversized tires the truck is lugging and calling for more boost. The gears will help raise the RPM and and lower boost. More boost means more fuel.
keep in mind this would really only be the case for truck with oversize tires. Also changing the gear ration will require tuning changes and the speedo will be further off
4:56 may be a little steep for a diesel also. 4:11's maybe a better choice
keep in mind this would really only be the case for truck with oversize tires. Also changing the gear ration will require tuning changes and the speedo will be further off
4:56 may be a little steep for a diesel also. 4:11's maybe a better choice
Last edited:
83GMCK2500
Active Member
rcpd34, you still have not told us how big his new tires are exactly. Did he lift/level it with the new tire combo, did he trim anything to fit bigger rubber? If his tires are the same size or very near it, then he does NOT need to correct diddly as far as the speedo/odo is concerned.
As Shawn mentioned the larger wheel/tire combo has changed the...rolling resistance (for lack of a better term) and also as JP mentioned a tune custom built for HIS truck professionally is the ideal way to go. It will likely net him a nice increase in power as well as economy. The extra power will compensate for the greater resistance.
Also, since his pockets allow, you should strongly urge him to Cognito the front of that thing: tie rods, support kits, upper control arms, basically show him what Nick (Nor-Cal Truck) did to HIS DUALLY.
As Shawn mentioned the larger wheel/tire combo has changed the...rolling resistance (for lack of a better term) and also as JP mentioned a tune custom built for HIS truck professionally is the ideal way to go. It will likely net him a nice increase in power as well as economy. The extra power will compensate for the greater resistance.
Also, since his pockets allow, you should strongly urge him to Cognito the front of that thing: tie rods, support kits, upper control arms, basically show him what Nick (Nor-Cal Truck) did to HIS DUALLY.