Changing gears.....help
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Junior User
Joined: Sep 2011
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Changing gears.....help
I am going to be replacing the stock 373 gears in my 2000 f350 with the 7.3 diesel..I am thinking about either 435 or the 456's. The truck will see very little dirt and will tow a 20' trailer(hopefully from New Jersey back to Cal). I have 37's on it with a 6" lift also. Have the edge CT programmer installed and need to set it up.. Any thought or ideas feel free to comment...
Thanks
Thanks
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Junior User
Joined: Sep 2011
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I understand that 456's are low but with an enclosed 20' trailer loaded with 3 bikes and a weight room plus other stuff. I think that it will help the tranny with a cross country tow. I researched the Edge programmer and everything I read said it was the best for the ford. Also, going to install cold air intake.....new with diesel so looking also for headers that may help... There is no cat it is a straight pipe from the motor back...also stock exhaust thinking about increasing the size. Was told that the bigger I go might Henderson the torque.....
This 7.3 is awesome and will keep it running till I give it too my grand kids....
Thanks for any help you guys give..
This 7.3 is awesome and will keep it running till I give it too my grand kids....
Thanks for any help you guys give..
Cargo Master
Joined: Sep 2007
Posts: 2,624
Likes: 7
From: OR and UT
Drop over to the diesel section and they will tell you what intake you need to run with that 7.3 PSD. They will also tell you to run a 6.0 PSD transmission cooler.
As for gears, 38" tires would probably love towing with 4.56 gears, but again, ask the PSD guys. I am a V10'er so all I can say is my V10 loves 4.30's and lots of gas.
As for gears, 38" tires would probably love towing with 4.56 gears, but again, ask the PSD guys. I am a V10'er so all I can say is my V10 loves 4.30's and lots of gas.
Moderator
Joined: Jul 2011
Posts: 6,513
Likes: 669
From: Sioux Falls Area
can't tell you what gears you want, so no help there. but ...
assuming your truck came stock with 265/75r16's
with 37's, 4.30's would get you back to your original gear ratio, so your speedometer would read within about 1mph of true speed.
@65 approx 2600rpm in 3rd, 1800rpm in 4th
@70 approx 2800rpm in 3rd. 2000rpm in 4th
@75 approx 3000rpm in 3rd, 2100rpm in 4th
if you go with 4.56's you would be adding about 5% more gear to the truck vs original. so, your speedo would be off about 5mph at 70mph.
@65 approx 2800rpm in 3rd, 2000rpm in 4th (speedo reads 70mph)
@70 approx 3000rpm in 3rd, 2100rpm in 4th (speedo reads 75mph)
@75 approx 3200rpm in 3rd, 2200rpm in 4th (speedo reads 80mph)
don't know what you want with your diesel, but that's about what you could expect to run down the road.....
assuming your truck came stock with 265/75r16's
with 37's, 4.30's would get you back to your original gear ratio, so your speedometer would read within about 1mph of true speed.
@65 approx 2600rpm in 3rd, 1800rpm in 4th
@70 approx 2800rpm in 3rd. 2000rpm in 4th
@75 approx 3000rpm in 3rd, 2100rpm in 4th
if you go with 4.56's you would be adding about 5% more gear to the truck vs original. so, your speedo would be off about 5mph at 70mph.
@65 approx 2800rpm in 3rd, 2000rpm in 4th (speedo reads 70mph)
@70 approx 3000rpm in 3rd, 2100rpm in 4th (speedo reads 75mph)
@75 approx 3200rpm in 3rd, 2200rpm in 4th (speedo reads 80mph)
don't know what you want with your diesel, but that's about what you could expect to run down the road.....
Thread Starter
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Junior User
Joined: Sep 2011
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Thanks for the info....looking at 456 that will help the towing and reclaim so of the fuel mileage I lost.....
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Senior User
Joined: Oct 2007
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Are changing the gears in these trucks a job a person could do without a lot of differential experience. Have rebuilt motors and gear boxes several times but always wanted to change my gears in my truck; just a little weary about it.
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Moderator
Joined: Jul 2011
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From: Sioux Falls Area
just for fun, i thought i'd see if this works or not.
i'm a spreadsheet nerd .... so i thought i'd show you what i'm talking about.
4.30's
4.56's
4.88's
5.13's
EDIT:
updated transmission gear ratios and changed the spreadsheet to make it easier to read and more usefull. switched the "speedometer reads" and "actual speed" columns to make them more usefull.
i'm a spreadsheet nerd .... so i thought i'd show you what i'm talking about.
4.30's
4.56's
4.88's
5.13's
EDIT:
updated transmission gear ratios and changed the spreadsheet to make it easier to read and more usefull. switched the "speedometer reads" and "actual speed" columns to make them more usefull.
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
Likes: 1,678
From: Stephensville WI
This site has some awesome automotive calculators that can help you decide what you want.
Automotive Calculators offer to you by Ford Trucks Enthusiasts | www.ford-trucks.com
To start, you had 32 inch tires and went to 37 inch tires. With a 3.73 differential, you now have an effective ratio of 3.22594 to 1, or we'll call it 3.23.
To get back to an effective stock ratio, you'd need to install a 4.3128 ring and pinion. (OK, call it 4.30, which is the closest stock gear set).
Since you'd like a little more towing power, 4.56 is not an outrageous ratio for your application, being just a little bit over your stock ratio of the 3.73 gears if you had kept the stock tires..
Automotive Calculators offer to you by Ford Trucks Enthusiasts | www.ford-trucks.com
To start, you had 32 inch tires and went to 37 inch tires. With a 3.73 differential, you now have an effective ratio of 3.22594 to 1, or we'll call it 3.23.
To get back to an effective stock ratio, you'd need to install a 4.3128 ring and pinion. (OK, call it 4.30, which is the closest stock gear set).
Since you'd like a little more towing power, 4.56 is not an outrageous ratio for your application, being just a little bit over your stock ratio of the 3.73 gears if you had kept the stock tires..
Mountain Pass
Joined: Nov 2010
Posts: 168
Likes: 8
From: Princeton Minnesota
I had the 4.56 gears in my 2001 F350 7.3 when I purchased it and did not appreciate the highway manners. At 65 mph the 7.3 was screaming for mercy just to keep up with traffic. The engine dronig made it difficult to talk in the cab to the person sitting next to you. If you want to stay under 60 mph, with a load of torque...the 4.56 is for you. I run 99% without any load in my truck and with the 4.56 gears got 11-13 mpg on the hwy. Just switched to 3.73's and the hwy manners are great but I really feel the loss around town. The 3.73's are a bit too high IMHO for lugging around town. I see the 4.10's coming into my realm in the near future. If your pulling a 20" trailer, the 4.30's may even be a better bet. I do not believe you will be happy with the 4.56 if your towing all hwy. I dont know how your speedo runs, but mine is about 10% under true speed according to my GPS.
Hope this helps. Do some searching around in the diesel forum, these guys are great!
Best regards!
Doug
Hope this helps. Do some searching around in the diesel forum, these guys are great!
Best regards!
Doug
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
Likes: 1,678
From: Stephensville WI
I had the 4.56 gears in my 2001 F350 7.3 when I purchased it and did not appreciate the highway manners. At 65 mph the 7.3 was screaming for mercy just to keep up with traffic. The engine dronig made it difficult to talk in the cab to the person sitting next to you. If you want to stay under 60 mph, with a load of torque...the 4.56 is for you. I run 99% without any load in my truck and with the 4.56 gears got 11-13 mpg on the hwy. Just switched to 3.73's and the hwy manners are great but I really feel the loss around town. The 3.73's are a bit too high IMHO for lugging around town. I see the 4.10's coming into my realm in the near future. If your pulling a 20" trailer, the 4.30's may even be a better bet. I do not believe you will be happy with the 4.56 if your towing all hwy. I dont know how your speedo runs, but mine is about 10% under true speed according to my GPS.
Hope this helps. Do some searching around in the diesel forum, these guys are great!
Best regards!
Doug
Hope this helps. Do some searching around in the diesel forum, these guys are great!
Best regards!
Doug
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Junior User
Joined: Sep 2011
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Now this is some good advice..so let me see...I have read that if I had stock tires then u are right the 456 are way to low and would kill me towing long distance with the noise and slow speeds. But due to the 37's that are on it I will be turning 70-75 mph at roughly 2100 rpm with the torque being lower. I have to take it to the guy that all south jersey goes to...M&M in sicklerville, nj.... He has a beast in his shop that he built from scratch. Definitely changing out the stock locks with warn manual lockers. That is one thing that is definite.. Let's see what he has to say on the gears.. I will let you know later today..
Again thanks guys for all the help..I know know what to ask and look for in selecting gears..
Next will be exhaust and air intake......let me hear from you guys about your opinions. Are there any headers for a diesel?
Again thanks guys for all the help..I know know what to ask and look for in selecting gears..
Next will be exhaust and air intake......let me hear from you guys about your opinions. Are there any headers for a diesel?