Need some help figuring out the gear ratio I need

ericlerouge · Jun 21, 2017

My truck is a 2009 b2300 with a 3.73 7.5 inch diff.
The original tire size is a 27.4 inches tall tire, I went to a 29.5 inches tall tire.

From the calculators in the tech section, 4.10 gears would bring me back close to original set up. I went to a local transmission shop, asked him a quote to change ring and pinion for a 4.10.

He told me I should get 4.56 gears because I mentioned to him I was having a hard time pulling my 1500 lbs travel trailer going uphill. the calculator tells me I would be at 3300 rpm at 65 mph...

What do you guys think?

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Mac · Jun 21, 2017

According to chart in tech library, that 3300 rpm would be in fourth, no overdrive which would drop it quite a bit.

ericlerouge · Jun 21, 2017

Oh ok, that sounds better..., Which brand of gears would you recommend? Motive, richmond, USA standard or svl ? SvL is 60 to 70$ cheaper than the other ones, I don't have a powerhouse, but I want to do this just once...

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ericlerouge · Jun 21, 2017

ericlerouge said:
Oh ok, that sounds better..., Which brand of gears would you recommend? Motive, richmond, USA standard or svl ? SvL is 60 to 70$ cheaper than the other ones, I don't have a powerhouse, but I want to do this just once...

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SvL is Dana, I think I'll be safe with those

pjtoledo · Jun 21, 2017

I have a 2005 2.3, manual tranny reg cab, 3:73 gears. so its about the same truck as yours.
having tried several tire sizes from the stock 27.4 to 29.5, the 3:73 will be adequate for light loads. downshifting to 4th will be a must when towing 1500 lbs.
downshifting to 4th on hills only is also a lot cheaper than re-gearing. so, how often do you tow? will it be worth it?

going from 27.4 to 29.5 is about an 8% taller tire.
going from 3:73 to 4:10 is 10% increase in gears.
downshifting from 5th to 4th will give you at least a 20% increase when needed.

friendly FYI, you probably already figured out that your stock brakes don't like the larger tires. they will not be happy at all when you tow 1500 lbs with the taller tires. I would be a little more careful when going down hill.

ericlerouge · Jun 22, 2017

pjtoledo said:
I have a 2005 2.3, manual tranny reg cab, 3:73 gears. so its about the same truck as yours.
having tried several tire sizes from the stock 27.4 to 29.5, the 3:73 will be adequate for light loads. downshifting to 4th will be a must when towing 1500 lbs.
downshifting to 4th on hills only is also a lot cheaper than re-gearing. so, how often do you tow? will it be worth it?

going from 27.4 to 29.5 is about an 8% taller tire.
going from 3:73 to 4:10 is 10% increase in gears.
downshifting from 5th to 4th will give you at least a 20% increase when needed.

friendly FYI, you probably already figured out that your stock brakes don't like the larger tires. they will not be happy at all when you tow 1500 lbs with the taller tires. I would be a little more careful when going down hill.

Thanks for your reply. You're right, I did a trip last year, and everything was ok, had to downshift to 4th and 3rd.

It was not that bad until I had to stop completely in the middle of a grade, I was at a red light and I was in traffic. It was really hard to get the truck going from there... maybe the driver is the fault here and I don't tow really often either, and maybe my trailer is 1600 lbs, and I had gear in the bed + me and my girlfriend...it all adds up...

I'm going on a little camping trip next week, I'll do some testing...

I'd like my truck to be able to cross the Rockies with the trailer...[emoji1] just in case....

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AzLizard · Jun 22, 2017

I have no input on the gearing.
But a set of brakes on your trailer will help. :icon_thumby:

Captain Ledd · Jun 22, 2017

Mine's a bit older, but I have 27" tires (235/75R15), and 4.56 gears with a 4 cylinder.

I'm right at 3,000 rpm @70 mph.

I tow tons of stuff with mine and love it. That rpm sounds like a lot but it really isn't bad. It works out to a 4.6L V8 puttering along at 1,500 rpm, plus at that rpm you're well into where those 4 banger actually make power. My Subaru with a 2.5L runs at 3,250 rpm at 70.

If you have 9" drums, definitely look into swapping a set of 10" drums on there while they're at it. Should be plenty in the wrecking yards. They need to pull the shafts anyways, so the backing plates will be easy to access. Ranger and Explorer plates are the same. Shoot, even the F150's 11" drum backing plate swapped onto my Explorer 8.8 (don't do that though, as the wheel bolt circle won't match).

When it comes to the 4 cylinders, do not fear the gear!

ericlerouge · Jun 22, 2017

Thanks for your replies I think I'm gonna go ahead with 4.56...

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cbr600rx7 · Jul 11, 2017

With almost a 30 inch tire and towing I would go with 4.56s and never look back. If you have drum brakes consider a disk brake axle swap while your at it.

ericlerouge · Aug 8, 2017

cbr600rx7 said:
With almost a 30 inch tire and towing I would go with 4.56s and never look back. If you have drum brakes consider a disk brake axle swap while your at it.

I finally ordered the 4.56 gears. I bought brand new brakes, drums and all, the way I drive while towing, I keep a safe distance in front... I never had brakes heating issues, worst case scenario, I'll find myself 10 inches backplates and upgrade...

I ordered USA standard gears from rock auto, I don't know much about gears, so I figured I'll get their more expensive... I don't think they are the best gears, but it's behind a 140hp four banger and I don't abuse it

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ericlerouge · Sep 1, 2017

Gears are installed, I'm happy so far with the results. The speedometer is way off, like 20 km/h off... I was wondering what's the best way to bring it back to normal. It's a 2009.

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gw33gp · Sep 1, 2017

I had an 89 Ranger with the 2.9L engine and 3.73 gears. I don't know the exact the size of the tire but it calculates to be 27.7". I switched to 31" tires and it did OK but taking out on a hill even when not towing took its toll on the clutch. After having to install a new clutch at around 60K miles, I had 4.10 gears installed. That worked perfect.

I would think 4.10 gears with 29.5'"tires should work well with the 4 cylinder engine but I don't have experience with towing with a 4 cyl engine, so a 4.56 may be better. I do know one thing though, I never ran in 5th gear when towing with the Mitsubishi transmission. I tried it once for a fairly short time and it overheated so much that I could not shift it until I stopped and let it cool down. I was fortunate to not continue driving or I am sure I would have destroyed the transmission. If you have the Mazda transmission, towing in 5th should be OK. I do it now with my current Ranger that has a Mazda transmission. My current Ranger has 4.56 gears and 31" tires on it when I tow about 3500 lbs with another 800 lbs or so on the bed. The 4.0 SOHC engine does make that much easer.

Captain Ledd · Sep 2, 2017

They make some electric speedometer converters, Currently I have a chart taped to my dash with Various speeds and their corresponding RPM in different gears.

Here's one, I've never used it though,

http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/category_id=311/mode=prod/prd126.htm

ericlerouge · Sep 2, 2017

gw33gp, i have the mazda trans, the 4.56 gears brings me right in the powerband of the engine as Captain ledd suggested me, it will save my clutch and transmission. .

Captain ledd, thanks for the inputs, I will look into those electronic boxes, but the chart is a bright idea. For now I use my gps, I may just continue to use it... I'm not so great at electronic stuff..

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Need some help figuring out the gear ratio I need

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