Gearing Advise Please
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Tuned
Joined: Sep 2002
Posts: 408
Likes: 11
From: saline USA
Gearing Advise Please
I am looking to buy a F350 single rear wheel, crew cab, long bed XLT with 7.3 gas engine. I tow bumper pull 35 foot Sunnybrook travel trailer, loaded the trailer is 9500lbs. So I am wanting advise on that weight of trailer whether to go with 4.30 gears or 3.73 and the ten speed trans. thanks for input. I tow mostly on the east coast.
Last edited by andrewzx92000; Dec 15, 2022 at 03:47 PM. Reason: forgot something
Cross-Country
Joined: Jul 2018
Posts: 51
Likes: 8
If you're gonna go big, might as well get the big gears too. Probably have to order it though, as dealers don't order stock with 4.30's for some reason.
I have a F-350 CCLB 4.30 but with the 6.2 and a similar sized TT. Gets the job done
I have a F-350 CCLB 4.30 but with the 6.2 and a similar sized TT. Gets the job done
Hotshot
Joined: Oct 2015
Posts: 19,732
Likes: 12,873
From: Wyoming
You'll hear that the 10r140 doesn't need the deeper rear gears. I'm not in that crowd. My opinion is that I want the gears that help the rest of the drivetrain work the easiest. I have the 6.7L engine but I got the 3.55 rear end. I tow in the Rocky Mountains, so almost every trip involves going over at least one mountain pass.
I tow, so I'm not going to be going over 70 mph anyhow.
I tow, so I'm not going to be going over 70 mph anyhow.
Laughing Gas
Joined: Oct 2003
Posts: 767
Likes: 132
From: Lynden, WA
Below are the transmission gear ratios with Ford's rear axle ratios. As I said earlier, 4.30's have a much better "gear split" then either 3.73 or 3.55.
Final Drive Ratio's
1st
4.30 x 4.615 = 19.84
3.73 x 4.615 = 17.21
3.55 x 4.615 = 16.38
2nd
4.30 x 2.919 = 12.55
3.73 x 2.919 = 10.89
3.55 x 2.919 = 10.36
3rd
4.30 x 2.132 = 9.17
3.73 x 2.132 = 7.95
3.55 x 2.132 = 7.56
4th
4.30 x 1.773 = 7.62
3.73 x 1.773 = 6.61
3.55 x 1.773 = 6.29
5th
4.30 x 1.519 = 6.53
3.73 x 1.519 = 5.67
3.55 x 1.519 = 5.39
6th
4.30 x 1.277 = 5.49
3.73 x 1.277 = 4.76
3.55 x 1.277 = 4.53
7th
4.30 x 1.010 = 4.34
3.73 x 1.010 = 3.77
3.55 x 1.010 = 3.58
8th
4.30 x 0.851 = 3.66
3.73 x 0.851 = 3.17
3.55 x 0.851 = 3.02
9th
4.30 x 0.687 = 2.95
3.73 x 0.687 = 2.56
3.55 x 0.687 = 2.43
10th
4.30 x 0.6321 = 2.72
3.73 x 0.6321 = 2.36
3.55 x 0.6321 = 2.24
Final Drive Ratio's
1st
4.30 x 4.615 = 19.84
3.73 x 4.615 = 17.21
3.55 x 4.615 = 16.38
2nd
4.30 x 2.919 = 12.55
3.73 x 2.919 = 10.89
3.55 x 2.919 = 10.36
3rd
4.30 x 2.132 = 9.17
3.73 x 2.132 = 7.95
3.55 x 2.132 = 7.56
4th
4.30 x 1.773 = 7.62
3.73 x 1.773 = 6.61
3.55 x 1.773 = 6.29
5th
4.30 x 1.519 = 6.53
3.73 x 1.519 = 5.67
3.55 x 1.519 = 5.39
6th
4.30 x 1.277 = 5.49
3.73 x 1.277 = 4.76
3.55 x 1.277 = 4.53
7th
4.30 x 1.010 = 4.34
3.73 x 1.010 = 3.77
3.55 x 1.010 = 3.58
8th
4.30 x 0.851 = 3.66
3.73 x 0.851 = 3.17
3.55 x 0.851 = 3.02
9th
4.30 x 0.687 = 2.95
3.73 x 0.687 = 2.56
3.55 x 0.687 = 2.43
10th
4.30 x 0.6321 = 2.72
3.73 x 0.6321 = 2.36
3.55 x 0.6321 = 2.24
Fleet Mechanic
Joined: Jan 2022
Posts: 1,410
Likes: 713
I think this is the best post regarding gearing I've seen. Sure smaller gears will work but 4.30s will work better. I have 4.30 in my 250 and is it overkill, yeah most the time, but I've never once said "I wish I opted for 3.55's.).
Cross-Country
Joined: Oct 2007
Posts: 98
Likes: 25
Made a spreadsheet out of it - feel free to play with it. If someone wants to try graphing the acceleration with various rear end ratios that would be interesting...
10R80 Gear Ratios
The way I look at it, if I'm driving 60 mph:
4.30 rear: 8th gear is 2302 rpm
3.73 rear: 7th gear is 2370 rpm
So really is there any big difference? 68 rpm. Engine is under almost identical load in either case. Let's try another one:
Hill climb, 50 mph:
4.30 rear: 6th gear is 2879 rpm
3.73 rear: 5th gear is 2971 rpm
Still only 98 rpm difference, and it's the 3.73 that has the lower load in both cases (higher rpm).
To me, the differences are too small to decide based on engine load at certain speeds. The 4.30 will have better grunt below 10 mph, the 3.73 will have an easier time cruising unloaded on the highway. Choose what suits you best...
Back when we had 3 gears (and maybe overdrive), this was a much different story because the ratio changed so much between gears that you couldn't just drop a gear to accomodate a smaller rear end ratio. I don't feel that's the case anymore.
I could also be completely wrong, both in my math and conclusions, so feel free to comment!
10R80 Gear Ratios
The way I look at it, if I'm driving 60 mph:
4.30 rear: 8th gear is 2302 rpm
3.73 rear: 7th gear is 2370 rpm
So really is there any big difference? 68 rpm. Engine is under almost identical load in either case. Let's try another one:
Hill climb, 50 mph:
4.30 rear: 6th gear is 2879 rpm
3.73 rear: 5th gear is 2971 rpm
Still only 98 rpm difference, and it's the 3.73 that has the lower load in both cases (higher rpm).
To me, the differences are too small to decide based on engine load at certain speeds. The 4.30 will have better grunt below 10 mph, the 3.73 will have an easier time cruising unloaded on the highway. Choose what suits you best...
Back when we had 3 gears (and maybe overdrive), this was a much different story because the ratio changed so much between gears that you couldn't just drop a gear to accomodate a smaller rear end ratio. I don't feel that's the case anymore.
I could also be completely wrong, both in my math and conclusions, so feel free to comment!
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Fleet Mechanic
Joined: May 2018
Posts: 1,765
Likes: 502
If you tow a lot on the coast, where it's flat, you likely won't notice or care. If you start venturing inland and getting into the foothills and mountains, you're going to want the 4.30's. Both will do fine though with the 10 speed. Keep in mind the real difference is low end grunt with the 4.30's so they'll make it a little easier to reverse and position a trailer (splitting hairs, I know, but may be an overlooked reason to opt for the taller gears).
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Laughing Gas
Joined: Jul 2011
Posts: 810
Likes: 494
Gear selection should be based on intended use of the truck.
It’s just plain silly for anyone to blindly give or take advice like below.
“get the deepest gear offered, muh 430’s”
”get the tallest gear offered to sip fuel”
OP says he will be part time towing 8K and daily driving the rest. 3.73 should pull what the OP needs with no sweat and provide him the best unloaded mpg.
I don’t believe for a minute that the UNLOADED INTERSTATE SET ON CRUISE mpg difference between the gear sets is .5-1mpg as most seem to claim.
It’s just plain silly for anyone to blindly give or take advice like below.
“get the deepest gear offered, muh 430’s”
”get the tallest gear offered to sip fuel”
OP says he will be part time towing 8K and daily driving the rest. 3.73 should pull what the OP needs with no sweat and provide him the best unloaded mpg.
I don’t believe for a minute that the UNLOADED INTERSTATE SET ON CRUISE mpg difference between the gear sets is .5-1mpg as most seem to claim.
Hotshot
Joined: Oct 2006
Posts: 10,190
Likes: 8,076
From: Texas
I am looking to buy a F350 single rear wheel, crew cab, long bed XLT with 7.3 gas engine. I tow bumper pull 35 foot Sunnybrook travel trailer, loaded the trailer is 9500lbs. So I am wanting advise on that weight of trailer whether to go with 4.30 gears or 3.73 and the ten speed trans. thanks for input. I tow mostly on the east coast.
Any differences will be minimal!
By the time you get all the answers here you will likely be more confused than ever! LOL
With that being said, what are the possdibilities of upgrading trailers? If you answer that question to yourself, you just answered your own question.
Laughing Gas
Joined: Oct 2003
Posts: 767
Likes: 132
From: Lynden, WA
"I am looking to buy a F350 single rear wheel, crew cab, long bed XLT with 7.3 gas engine. I tow bumper pull 35 foot Sunnybrook travel trailer, loaded the trailer is 9500lbs. So I am wanting advise on that weight of trailer whether to go with 4.30 gears or 3.73 and the ten speed trans. thanks for input. I tow mostly on the east coast."
I must have missed the part where he asked about fuel economy.
To me, the differences are too small to decide based on engine load at certain speeds. The 4.30 will have better grunt below 10 mph, the 3.73 will have an easier time cruising unloaded on the highway.
I could also be completely wrong, both in my math and conclusions, so feel free to comment!
I could also be completely wrong, both in my math and conclusions, so feel free to comment!
Cross-Country
Joined: Oct 2007
Posts: 98
Likes: 25
OK, 4.30 trucks will without a doubt when cruising unloaded have a much easier time because the load (either with trailer or without) will be easier to move, My 99 in signature had 3.73's and 6 speed manual, achieved a best of 14.3 mpg average running unloaded at 65-70 mph over a 1200 mile trip from Seattle to Phoenix. After swapping out the 3,73;s to 4,30;s it achieved 14.4 on the return trip from Phoenix to Seattle running 65-70 mph. The bonus was not having to take it out of overdrive nearly as often as when running 3.73;s. It seemed that every hill I had to drop out of overdrive. Granted the OP is using much more power, a much better transmission from a gear ratio stand point and more effective gear splits but there is no way the load is less on 3.73 geared trucks.
Your comment about loads being easier to move with the 4.30 is only really true at low speeds (< 10 mph) - above that the transmission having such close gear spacing pretty much makes it moot. IMHO of course...
