Rear axle ratios, tire size, trans and engine combos

[RJacobsen]

I just posted this link on another thread but thought it should have its own. If you are trying to decide on rear axle ratios, transmission types, tire sizes, and engine combinations this will come in very handy. http://www.gtsparkplugs.com/GearCalc.html

[Naumoff]

Thanks Rod. Great site
**will have to edit later. Our forum tightens everything up****Happy Easter
Here is my set up

*******************************
Final Gear Ratio : 3.31
Tire Size : 295-55-15
Max Power RPM : 6300
Limit RPM : 7000
*******************************
*********************
Gear Ratio Compound
*********************
1 2.320 7.679
2 1.690 5.594
3 1.290 4.270
4 1.000 3.310
***************************************
Gear MPH/1000 MPH @6300 MPH @7000
***************************************
1 10.77 68 75
2 14.78 93 103
3 19.36 122 136
4 24.98 157 175
********************************************
MPH RPM (in Gears)
********************************************
1 2 3 4
********************************************
5 464 338 258 200
10 929 677 516 400
15 1393 1015 775 601
20 1858 1353 1033 801
25 2322 1691 1291 1001
30 2786 2030 1549 1201
35 3251 2368 1808 1401
40 3715 2706 2066 1601
45 4180 3045 2324 1802
50 4644 3383 2582 2002
55 5108 3721 2840 2202
60 5573 4060 3099 2402
65 6037 4398 3357 2602
70 6502 4736 3615 2802
75 6966 5074 3873 3003
80 5413 4132 3203
85 5751 4390 3403
90 6089 4648 3603
95 6428 4906 3803
100 6766 5164 4003
105 5423 4204
110 5681 4404
115 5939 4604
120 6197 4804
125 6456 5004
130 6714 5204
135 6972 5405
140 5605
145 5805
150 6005
155 6205
160 6406
165 6606
170 6806
175 7006
********************************************
Gear Change RPM drop (change @6300) RPM drop (change @7000)
************************************************** ***********
1->2 -1711 (To 4589) -1901 (To 5099)
2->3 -1491 (To 4809) -1657 (To 5343)
3->4 -1416 (To 4884) -1574 (To 5426)
************************************************** ***********

[RJacobsen]

I'm not sure why the copy/paste turns out that way but the charts on the site are interesting to look at.

I was trying to decide between the 2 rear axles I have (4.09 or 3.54) for my 289 HIPO- 5 speed combo and came up with 200 mph at 6500 rpms with the 4.09 rear end, not that I think the engine will be able to do it but I'm going with the 4.09 now because I know I'll be short on torque and high on rpms.

[RJacobsen]

Tony, Looks like your good to 160 mph, Hang on :D

[Naumoff]

Rod,

I will want to put the big brakes up front before I attempt 160.:D

In the 1/4 mile I can run through the traps in third gear with my set up when I do a soft launch.

What is the redline on your smallblock? 9000? I guess a 4.09 wouldn't be bad.
I ran a 4.10 in my Galaxie.

[RJacobsen]

Tony, I'm not sure about the redline, I'm going to limit it to 7000 for now and see how it acts, that should be plenty to get into trouble with. I have a different cam now than what I used when the engine was in my Mustang but 7000 was not a problem before.

[Naumoff]

It will be interesting to see how you like them.

[Slither]

Tony, what tires are you running these day?

[YerDugliness]

Thanks for posting that, Rod.....I'm looking at a used turnkey this coming weekend and I've been a bit reluctant b/c it has a T5 with a 3.7 rear gear. The 3.35 first gear on the T5 would seem to make the first gear all but unusable for anything except parades, but the gentleman who owns and drives it says he uses it every time from a standing start. He claims 18 mpg with a 5.0 HO/T5 from a 1989 Mustang GT. Must have pretty tall tires on it, I know he has huge rear fenders and the steamrollers fill them all the way up.

Nice car, but, sadly, a 427 body and not a Unique.....still hoping for my 289 FIA someday! When that happens, I'll certainly :banana: !!

I'm sure this chart will be helpful.....I'd doubt that the speedometer gear is correct with those huge rear tires, so I'll measure the diameter of the tire (loaded/vertical diameter, correct??) and print off the chart, until I can get the gear changed out. This one is exactly the wrong color--red. Cops stop red cars just for fun, I figured that out long ago.

Dugly :cool:

[RJacobsen]

dugly, the site allows you to either put in the tire size by measurement or by the numbers on the tire.

[YerDugliness]

dugly, the site allows you to either put in the tire size by measurement or by the numbers on the tire.

I notice it also has a place to put in the wheel width.

Which do you think would be more accurate? I'll need to rely on this to avoid tickets until I can get the speedometer calibrated.

It has a 9" Ford posi unit, the tranny is the weakest link, so none of this: :3g:

Thanks!

Dugly ;)

[scott h]

in my experience an accurate speedo has no correlation to avoiding speeding tickets, it just verifies the cops statement as to how fast you were really going!

[RJacobsen]

I notice it also has a place to put in the wheel width.

Which do you think would be more accurate? I'll need to rely on this to avoid tickets until I can get the speedometer calibrated.

It has a 9" Ford posi unit, the tranny is the weakest link, so none of this: :3g:

Thanks!

Dugly ;)

I would just put in the tire size numbers as per the example

[Slither]

Nice car, but, sadly, a 427 body and not a Unique.....still hoping for my 289 FIA someday! When that happens, I'll certainly :banana: !!

Dugly :cool:


Hold out for the Unique 289 car:cool:[thumb]!

[YerDugliness]

Hold out for the Unique 289 car:cool:[thumb]!

Sure wish I could do so, but this kit I'm going to see is a real value.....a turn-key, with carb'ed 5.0 HO/T5 from a '89 Mustang GT. Recent upgrades include fuel cell foam in the gas tank, Flaming River steering rack/components and a rather involved ride height adjustment performed by Keith Craft in Texas.........already painted and striped, all it needs to be "pristine" is some new carpeting. All this for an asking price of $19.5K, essentially less than just a kit from Unique.

I'll eventually be a Unique owner, I will have my 289 FIA model and the Unique is way ahead of the ERA due to it's incredible value and greater availability. This 427 model is just an attractive distraction at the moment.

At this point I'm ready to be making a move of some kind and the used driver seems like quite the bargain and has a motivated seller. I'm going to see it Wednesday.


in my experience an accurate speedo has no correlation to avoiding speeding tickets, it just verifies the cops statement as to how fast you were really going!

ROTFLMAO, Scott!! Sadly, that's been my experience, too, and is what I'm hoping to avoid at this time [thumb] .

Dugly :cool:

[Slither]

Well... good luck[thumb], and don't let your anticipation get in the way of your better sense. If is isn't good, RUN, don't walk, away;)! Keep us posted.

[Naumoff]

Tony, what tires are you running these day?
Paul, I still have my Firestone Indy 500 and a set of Goodyear Billboards.

[Slither]

Paul, I still have my Firestone Indy 500 and a set of Goodyear Billboards.

Are you still liking the Firestones?

[Naumoff]

Paul, they are OK. The Billboards are awesome once they are heated up. The grip is very noticable. But I have been told by a couple of people that run the Avons that they are way better than the Billboards.
I will replace the Firestones with Avons.
They are pricy but my thoughts are we have a lot invested in the car why put cheap tires on them.

I haven't checked but have also heard that Firestone no longer make the Firehawks in 295 15s.

[TurnpikeBoy]

.....They are pricy but my thoughts are we have a lot invested in the car why put cheap tires on them......

You must work for the Guv'mint. ;)

[Naumoff]

You must work for the Guv'mint. ;)

The guv'mint would pay too much for cheap out dated tires. :)