Jump to content
HybridZ

3.36 Rear end


BAlford

Recommended Posts

Looks like I am going to have to change my rear end noisey rear end. I saw a post about new in the box 3.36 ring and pinions some place on her in the last 10 days or so. Does anyone remember where it was.

 

Also I read a post by about a 3.36:

Rick Bowers

Member

Member # 2349

 

Tried to e-mail him and could not get the e-mail to work. If you see this please contact me at.

 

waskomtexas@waskomtexas.com

Link to comment
Share on other sites

If I am figuring my math right these are the speeds that my car would be traveling at 3000 RPM. My tires are 76" around the tire. I understand that a tire jacked up and a tire setting on the ground or pulling may not be the same distance around the tire.

 

My car was a 1982 280ZX turbo automatic with CV joints, it now has a Chev 350 with a turbo 400. The ratio that I have in the car is 3.54 to 1 and when I am turning 3000 we checked with another car and I was doing 60 MPH.

 

If I replace the rear end with a 3.36 to one I figure that I will be going nearly 65 MPH.

 

A 3.90 to 1, which does not interest me, would be only traveling 55 MPH.

 

Does the 3.36 ring gear have the same bolt pattern and diameter bolt as the 3.54 and will it fit in the housing?

Link to comment
Share on other sites

Originally posted by BAlford: If I am figuring my math right.., at 3000 RPM.., My car now has a Chev 350 with a turbo 400.., The ratio is 3.54.., and when I am turning 3000 .., I was doing 60 MPH.., If I replace the rear end with a 3.36.., I will be going nearly 65 MPH
BAlford,

 

For starters when working the math for speed and rpm you dont want to use the circumferance of the tire; rather, it is much easier to use the diameter of the tire.

 

My 78z has 190/70/14" tires.

 

The 190 rep's the Section Width and is measured in mm's (millimeters): the Section Width simply means the "Distance Between the Sidewalls". The mm's will have to be converted into inches; the conversion factor is 25.4, so we will divide the 190mm's by 25.4 to get the Section Width in inches.

 

The 70 rep's the Aspect Ratio and is a Percentage (%) of the Section Width. A (%) is a fraction of the whole. In our case the Section Width is the whole while the Aspect Ratio is the fraction. So, the 70 actually rep's .70, or 70% if you will. So our Aspect Ratio will be .70% of our Section Width: Remember, the Aspect Ratio is a fancy word for "Sidewall", as you know there are two Sidewalls, one at the top of the tire and one at the bottom of the tire: or one on each side-depending on how you look at it.

 

And of course, our 14" rep's the actual diameter of our wheel.

 

Now to put all this into a working formula, you would write the formula like so:

 

Tire Diameter:

= [(Section Width / 25.4) x Aspect Ratio/100]x2) + Rim"

 

(You would plug your tire figures into the formula and work it accordingly), but for now, plug my tire dimentions into the formula and work it like so:

 

Tire Diameter:

= [(190/25.4) x 70/100)x2] + 14"

= [(7.48" x .70) x2] + 14"

= [(5.236"x2] + 14"

= 10.472 +14"

= 24.472"

 

 

Since you didnt give your tire's dimensions we will have to work the math using the known variables you did give:

 

1)60mph

2)3000rpm's

3)3.545 differential

4)400TH...1:1 Ratio in 3rd gear

 

The formula for determining a tire diameter with these known variables is as follows:

 

Tire Diameter = MPH x Gear Ratio x 336 / RPM

 

work the math like so:

Tire Diameter:

= 60mph x 3.545 x 336 / 3000rpm

= 71467.2 / 3000

= 23.82"

 

Now we can use that figure with the rpm and or speed formula, which is similar to the Tire Diameter formula. If we assumed your friends rpms were correct and your odometer is also correct; these are the formulas:

 

RPM = MPH x Gear Ratio x 336 / Tire Diameter

 

MPH = RPM x Tire Diameter / Gear Ratio x 336

 

If we were to use the 23.82" Tire Diameter and go with your new rear gear ratio of 3.36 then you could again use your 3000rpms to determine MPH, like so:

 

MPH = 3000rpm x 23.82" / 3.36 x 336

MPH = 71460 / 1128.96

MPH = 63.297mph

 

What you really need, besides a rear end that is not noisey, is a 700R4 AOD trans; then your cruise speeds would be pleasant and the wear-n-tear to the engine would be greatly minimized. Get the lower rear end & an AOD & then you'ld be sittin high on the hog; as the budget allows of course!

 

Kevin,

(Yea,Still an Inliner)

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...