New Gears for 38 Inch Tires? - Ford Powerstroke Diesel Forum
6.7 Performance Parts Discussion 6.7 Performance Parts Discussion

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 21 Old 05-27-2014, 07:11 AM Thread Starter
POWERCHOKER
 
Dantron's Avatar
 
Join Date: Sep 2013
Location: Texas
Posts: 2,727
Thanks: 48
Thanked 111 Times in 102 Posts
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Feedback Score: 1 reviews
New Gears for 38 Inch Tires?

I'm using stock 3.55 gears for 38's right now. Do I need to change gears? I don't necessarily feel a need to, but I don't want to harm anything if that's a possibility. Any thoughts?
Dantron is offline  
post #2 of 21 Old 05-27-2014, 08:46 AM
Compression Ignition Addict
 
HighHP's Avatar
 
Join Date: Jan 2014
Location: Fort McMurray, AB
Posts: 1,466
Thanks: 30
Thanked 105 Times in 93 Posts
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Feedback Score: 0 reviews
Wont harm anything except mileage, alot of guys will tell you the trans gearing makes up for the higher gears. I am by no means a gear master but from previous vehicles Ive had rule of thumb was usually 4.10s for 37" tires, but theres success stories with these trucks and guys running 38's with 3.55s and 3.73s.

What did you do about getting the speedo correct? I havent looked into it lately but last I had heard it wasnt possible over 34"?

2013 - F350 CCLB. - 8" Lift on 37s. H&S XRT w/ CTS. Sinister EGR Delete. MPD CCV Delete. Wicked Wheel 2. SDP Downpipe. No Limits CAI. 5" FloPro. Retrofit HIDs.

HighHP is offline  
post #3 of 21 Old 05-27-2014, 09:14 AM
Compression Ignition Addict
 
Randy_270's Avatar
 
Join Date: Sep 2012
Location: Manitoba, Canada
Posts: 557
Thanks: 18
Thanked 37 Times in 34 Posts
Mentioned: 0 Post(s)
Quoted: 2 Post(s)
Feedback Score: 0 reviews
There is a member on here with some Hypertech inline module that gets plugged in and can correct the speedo for any tire size but as far as I know with the H&S you can only correct up to 34" tires as well. I'd say re-gear Dantron but that's just me. If you don't plan on towing or going to the mountains then you should be fine with the 3.55s. If I go above 35" tires I would re-gear but that's because I live in a hilly arear and want to tow with my truck.

2011 F350 Lariat FX4, CCSB, 6.7, 3.55s, 325/65R18 Duratracs, Carli 4.5" Pintop, Flo-Pro, S&B intake, H&S w/ SPE tuning.
2011 Explorer Limited 4WD on 17x7.5s Core Racing Diablo 2s with 245/70R17 Duratracs
Randy_270 is offline  
post #4 of 21 Old 05-27-2014, 09:33 AM Thread Starter
POWERCHOKER
 
Dantron's Avatar
 
Join Date: Sep 2013
Location: Texas
Posts: 2,727
Thanks: 48
Thanked 111 Times in 102 Posts
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Feedback Score: 1 reviews
Yep. The computer still won't adjust for anything bigger than 34's. You have to buy a Hypertech or Pro Comp in-line calibrator, for like $200. Not worth it to me. I don't really monitor my fuel economy and a cop will usually give you a warning if you play dumb saying that you had the cruise control set to the speed limit. I will most likely re-gear to 4.10's one day, but it's not a high priority on my to do list (turbo first!).
Dantron is offline  
post #5 of 21 Old 05-27-2014, 10:40 AM
Premium Member
 
lowmpg's Avatar
 
Join Date: Mar 2014
Location: Annapolis, MD
Posts: 339
Thanks: 15
Thanked 18 Times in 18 Posts
Mentioned: 0 Post(s)
Quoted: 32 Post(s)
Feedback Score: 0 reviews
You can easily run the stock 3.55s. speedo will be roughly 2-3mph off around 45+. The ProComp tool does nothing over 34", there is apparently a code issue from Ford that limits this axle ratio/tire combination (spoke to Edge and SCT, same answer).



2013 F350 No Limit EGR Delete, DPF delete, Gearhead Tunes, aFe Momentum intake, Zone 6" lift, 37x13.5x18 Open Country MT, HID lights, 20" Rough Country LED bar, Flo Pro and Banks pipes, 17mpg
lowmpg is offline  
post #6 of 21 Old 05-27-2014, 10:52 AM
Compression Ignition Addict
 
Randy_270's Avatar
 
Join Date: Sep 2012
Location: Manitoba, Canada
Posts: 557
Thanks: 18
Thanked 37 Times in 34 Posts
Mentioned: 0 Post(s)
Quoted: 2 Post(s)
Feedback Score: 0 reviews
Quote:
Originally Posted by lowmpg View Post
You can easily run the stock 3.55s. speedo will be roughly 2-3mph off around 45+. The ProComp tool does nothing over 34", there is apparently a code issue from Ford that limits this axle ratio/tire combination (spoke to Edge and SCT, same answer).
You're talking about the OBD2 plug in module, I was talking about one that gets plugged into your gauge cluster. There is a member on this forum that has his speedo corrected for 38" tall tires.

2011 F350 Lariat FX4, CCSB, 6.7, 3.55s, 325/65R18 Duratracs, Carli 4.5" Pintop, Flo-Pro, S&B intake, H&S w/ SPE tuning.
2011 Explorer Limited 4WD on 17x7.5s Core Racing Diablo 2s with 245/70R17 Duratracs
Randy_270 is offline  
post #7 of 21 Old 05-27-2014, 10:58 AM
Premium Member
 
lowmpg's Avatar
 
Join Date: Mar 2014
Location: Annapolis, MD
Posts: 339
Thanks: 15
Thanked 18 Times in 18 Posts
Mentioned: 0 Post(s)
Quoted: 32 Post(s)
Feedback Score: 0 reviews
Wow, yeah I was talking about the 200.00 unit here: http://www.summitracing.com/parts/ex...05-1/overview/



2013 F350 No Limit EGR Delete, DPF delete, Gearhead Tunes, aFe Momentum intake, Zone 6" lift, 37x13.5x18 Open Country MT, HID lights, 20" Rough Country LED bar, Flo Pro and Banks pipes, 17mpg
lowmpg is offline  
post #8 of 21 Old 05-27-2014, 11:06 AM Thread Starter
POWERCHOKER
 
Dantron's Avatar
 
Join Date: Sep 2013
Location: Texas
Posts: 2,727
Thanks: 48
Thanked 111 Times in 102 Posts
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Feedback Score: 1 reviews
Yeah. The in-line speed-o-meter calibrator is hardcore and will do the trick, but (+/-) 5 MPH isn't that big of a deal to me. As far as the 3.55's, I haven't been able to tell if it's lacking because I don't have anything to compare it to. I just don't want to harm the transmission or something.
Dantron is offline  
post #9 of 21 Old 05-27-2014, 11:09 AM
Premium Member
 
lowmpg's Avatar
 
Join Date: Mar 2014
Location: Annapolis, MD
Posts: 339
Thanks: 15
Thanked 18 Times in 18 Posts
Mentioned: 0 Post(s)
Quoted: 32 Post(s)
Feedback Score: 0 reviews
Hypertech has one as well:
Hypertech 730120 In-Line Speedometer Calibrator Module



2013 F350 No Limit EGR Delete, DPF delete, Gearhead Tunes, aFe Momentum intake, Zone 6" lift, 37x13.5x18 Open Country MT, HID lights, 20" Rough Country LED bar, Flo Pro and Banks pipes, 17mpg
lowmpg is offline  
post #10 of 21 Old 05-27-2014, 11:14 AM Thread Starter
POWERCHOKER
 
Dantron's Avatar
 
Join Date: Sep 2013
Location: Texas
Posts: 2,727
Thanks: 48
Thanked 111 Times in 102 Posts
Mentioned: 0 Post(s)
Quoted: 1 Post(s)
Feedback Score: 1 reviews
I think that's something I'll get when I switch gear ratios in a few years..
Dantron is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Ford Powerstroke Diesel Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome