Gear ratios
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Senior User
Joined: Oct 2004
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From: Auburn, OH
Gear ratios
I'm looking to get a truck pretty soon and have a few that I am going to look at this weekend. They are both 300ci manual, 4x4. One is a 4spd, one is a 5spd. My friend has an 82 4spd, 4x4 with the grany gear for first which makes it a 3spd for most driving. I need something that will get down the road alright since I am in college and have to make a 4 hour freeway drive home but since other than a daily driver the truck will be for play it has to have 4wd. Anyway back to the point. What is the best combination to look for that will have a good highway gear and still be ok for some light/moderate off roading? Also, is there anyway to tell from the vin or other markings what is in the trucks?
I'm sure if there was a search button or I had a week I could find this all in the history but I've been working on computers the last two days and still have a day at work left before I get to actually do somethign else.
I'm sure if there was a search button or I had a week I could find this all in the history but I've been working on computers the last two days and still have a day at work left before I get to actually do somethign else.
Super Moderator
Joined: Apr 2004
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Go for the 5 speed.
If the 4 speed is od, it has a terrible 2nd to 3rd gap.
If the 4 speed is not od, you have a low 1st, and will be wringing it out on the hiway with a 1:1 4th.
The 5 speed will lack the ultra low 1st, but you have a low range in the transfer case, right? And since you are talking light to moderate off roading, you are not going to be rock crawling needing the compound low 1st w/low range. Correct?
The 5 will have OD which will send your revs low as the price of gas goes high.
Just my biased opinion after a $45 fill up in my little car.
If the 4 speed is od, it has a terrible 2nd to 3rd gap.
If the 4 speed is not od, you have a low 1st, and will be wringing it out on the hiway with a 1:1 4th.
The 5 speed will lack the ultra low 1st, but you have a low range in the transfer case, right? And since you are talking light to moderate off roading, you are not going to be rock crawling needing the compound low 1st w/low range. Correct?
The 5 will have OD which will send your revs low as the price of gas goes high.
Just my biased opinion after a $45 fill up in my little car.
Post Fiend
Joined: Nov 2001
Posts: 5,871
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From: Coutts Canada
Yes thee 5sp will be nice for highway driving, but if its the mazda 5sp from a newer half ton (that tranny seems to me is a swapped in one cause all the manual OD's in these trucks were 4sp) then it isn't going to last half as long as that 4sp will cause the tranny more meant for 1/4 ton trucks. But if its a ZF 5sp out of a 3/4 to 1 ton you will get a better 1st gear and a pretty bullet proof tranny. So be sure to ask where that tranny came from.
Posting Guru
Joined: Jan 2003
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From: SE Texas
The 2 common gear ratios in the 80's trucks are a 3.00 and 3.50 with the 9" rear axle, or 3.08 and 3.55 with the 8.8" (starting after 1983 in some). The mileage will be marginally better with the 3.00 ratio, but will not have any power with tires over 30" tall for offroad. The Mazda 5-sp OD manual came along around 85/86 and tends to have more problems than the 4-sp T18, (the one your buddy probably) has with the granny low 1st. You can't tell anything from the VIN #, but look at the codes on the driver's-side door jamb. You can also crawl underneath and look for the ID tags on the axles for the ratio. That's the best way, as you will be checking for any fluid leaks, too.
Elder User
Joined: Oct 2004
Posts: 984
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From: Winnipeg, Manitoba
I'd personally go for the 4 speed, and install slightly taller tires, which will raise the over-all gear ratio a bit. Most people ignore the granny low, but I've found over the years, using it to get you moving not only helps fuel mileage, but saves your clutch as well. You tend to slip the clutch a bit more in second gear, and in the long run, this contributes to worn parts, as well as poor fuel mileage. With the slightly taller tires (say up to 31 inch for a stock truck) you'll see a mild improvement in gear ratio's, and mileage on the highway. The 300 I-6 was never really known as a mileage engine, but it's reliable as the day is long, and has some stump pulling tourque, both are good things in the 4x4 world.
Laughing Gas
Joined: Apr 2003
Posts: 837
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From: Minnesota
I guess I'd side with RR4E on this one. The early 5OD's were weak.
I had two different 6.9/4creeper's, an '85 with 4.10's and the other was an '84 with 3.55's. Neither was a good axle ratio (IMHO) for the 6.9 engine w/std tire sizes. With any kind of uphill grade or soft ground I had to start the 3.55 truck in 1st and for the most part ended up driving it like a straight 4 speed, like has been suggested to you. The 4.10 truck started well in 2nd but if you had a load to start out with and had to use 1st to get rolling you were stopped before you could get into second
Good Luck with it,
Roger
I had two different 6.9/4creeper's, an '85 with 4.10's and the other was an '84 with 3.55's. Neither was a good axle ratio (IMHO) for the 6.9 engine w/std tire sizes. With any kind of uphill grade or soft ground I had to start the 3.55 truck in 1st and for the most part ended up driving it like a straight 4 speed, like has been suggested to you. The 4.10 truck started well in 2nd but if you had a load to start out with and had to use 1st to get rolling you were stopped before you could get into second
Good Luck with it,
Roger
