Barfly

340/727 Dodge Dakota:

I found ring and pinion gears for my rear end.
I believe whats in there now is a 3.15 ratio.
The gears I found come in several ratios.
One sticks out for me is 4.10 but I am wondering what you guys might think? We want to do well in the 1/8 mile strip but I want to be able to travel 65 mph down the road too

Also I'm listing two different manufactures at two very different price points, if you have any opinion on which would be best, please.

Here are links to the gears I found,

Richmond

USA Standard Gear

thank you very much for any input.

Joe.

blue 68 gts

Joe,

The 4:10s will def get you a faster 1/8th time, but you may not be able to go 65mph down the road...

4:10s in my car I can only do 50 and its already at 3000 RPM. Though, diff size wheels/tires changes everthing.

I would say go with something between 3:23s and 3:55's.. Good all around gears for freeway/highway and drag strip

1966sportfury

with 24" tires and 4.10 you should be doing 3444 rpm at 60mph (with a final drive of 1:1)

heres the formula

miles per hour x Axle Ratio x 336 divide by tire diameter 60x4.10x336/24=3444 rpm

78D200

What tire size are you running? Any type of traction device in the rear axle as well? What is the rear axle?

Barfly

I was just calculating the tire height this very moment.

the rear tires are P235/60R16 which if I'm figuring right is just about 27" tall.

I don't know about the traction device or what you are asking when you say "what is the rear axle" .

Barfly

@ 1966sportfury
thank you for the formula!
In the formula what is the '336'

Joe

78D200

Traction device - Is the carrier open or is there a limited slip or locker or spool?

What is the rear axle - which rear axle do you have in the vehicle now? 8 1/4? 9 1/4? dana 60?

blue 68 gts

235/60s are 26.1

255/60s are 27.1"

67 GTX

really?
that is pretty high.

67 GTX

i would just go with 3.55
they'll give you the best of both worlds

78D200

That is if you had a 15" wheel. Joe said he has 16"

Barfly

Hey blue, I think you must be figuring 15" wheels.

I sure appreciate everyones help here.

Joe.

67 GTX

to be comfortable on the highway, going 60, you really want to be at less than 3000rpm
that'll also help save some $$$

78D200

What do you have?

If I had to say what to go with, I'd say 3.55-3.73. You really need to know what you actually have though for gearing. It would suck to find out that you have 3.23 in an 8 1/4 and end up getting the same gearing.

Barfly

I'll jack it up tomorrow and do the revolution test. Right now based on an article I read about the original equipment and using the formula above, I think I have the 3.15 ratio. I'm real confident it's the 8 1/4" rear end though based on the oval 10 bolt cover in this article.

It's an interesting formula sportfury posted. A small amount of change in the gear ratio makes a considerable amount of change in the rpm's. While it takes a much larger amount of change in tire size to effect the rpm's very much at all.

My speedometer is slow by 10 mph so I started to think my tires were to large. But looking at the above referenced article I find while they are supposed to be 15" wheels, but my the tires are actually only 1/2" larger than what came stock on these trucks. So I'm guessing now the speedometer error must be caused by the transmission??

I have also read about "master" and "basic" rebuild kits available for replacing the ring and pinion. Are these necessary or can I just buy the ring and pinion and get away with that?

Thanks again.
Joe.

78D200

You will probably need to change out your speedo gear but I would wait til after you change your axle gears.

As far as install kits go, I usually always get the amster kit as it will supply you with everything that you need (carrier bearings, inner/outer pinion bearings, carrier/pinion shims, pinion nut and washer, seals, crush sleeve, etc.). The basic kits usually are only bearings and or shims.

Depending on the rear axle that you have, there may be a carrier break. Meaning that there are two different carriers out there that will fit depending on the gear ratio. There is a series 3 and series 4 carriers.

First thing to do is to figure out exactly what axle you have and what you have for gearing. Easy way to find out is to read the ID tag on the diff cover (as long as it is still there) or pull the diff cover off and read the "teeth count", it should say something like "39-11". Take the 39 and divide it by the 11 and you have your gear ratio of 3.55.

78D200

Here is a very good article on "Gear setup" that everyone who has setup gears or that want to try it should read. Bill does the whole article based on a D60 but the same pricipals apply to a lot of the axles out there today. This article has helped me rebuild D30s up to D60s, some 14B and a few 8.8 axles.

http://www.pirate4x4.com/tech/billavista/Gear_Setup/

Barfly

Thank you for the link. And I think that kinda settles it for me

I'm a back yard guy, no garage, hardly any tools (other than electrical hand tools) I'm thinking this is more than a little over my head.

I think I will turn this over to someone with the know how and tools.
I to do hate that, but you gotta know your limits right

Thanks guys.

Joe.

78D200

It certianly wasn't ment to discourge you from doing the job. If you want to see it done or help with it, I would talk around a local forum and see who does them in their garage. Maybe you can help them with it and see how it's done.

I know most shops around me charge a minimum of $300 (most are $400) to swap gears. I only charge $150 but also can't get it done as fast as the shops and don't warranty anything, but i am willing to help out if there is a problem.

78D200

If you do get everything to do the job, make sure that the bearings are Timken (made in the USA and are very good quality). As far as gears go, Richmond set up very nice and are very, very good quality. USA gears, Yukon, and Genuine gears all set up nicely. I'm running Genuine in my D44s and have run Richmond gears in front D60s before.

Barfly

No worries.

Now I'm completely confused and feel like I'm missing something simple.

I jacked the rear end up and marked the rear tire and yoke on the drive shaft. For 1 complete turn of the drive shaft I get almost exactly 3/4 of a turn on the wheel. I got confused.

Turned the rear wheel exactly 6 complete turns and got just about 8 turns on the shaft. 8/6 = 1.3

I don't know, is it possible I have a 1.3 gear ratio? Is that right?

78D200

You need to hold one wheel while spinning the driveshaft. This way, the other wheel spins correctly.

Proper way of figuring out rear axle gear ratio - Place a block of wood infront of and behind one of the front wheels. Have the transmission in neutral. Raise one rear tire high enough for you to get under the vehicle safety, don't forget to place a jackstand under the rear axle for safety. With one wheel in the air, mark the inside of the tire and a spot on the brakes or body that you can easily see. Start to rotate the pinion yoke by hand and count how many times the pinion yoke rotates around til the tire makes one full rotation. This is about the ratio that you have.

67 GTX

you could also put a mark on the driveshaft, but Tim's way works too
I have done this loads of times

67gtxclone

Barfly, I also like to do as much as I can on my own cars, but changing gears is best left to someone who has the experience and tools. I am using 3:55 and I am happy with the "off the light performance" as well as highway driveability.