Think I'm gonna swap over to 3.73's

[MB750]

Originally I was thinking my 3.27 gears would be ideal. Something more relaxed for cruising but still not too short around town. Now as I've put a few miles driving around town I'm getting annoyed at the 30ish mph cruise. It's either a too high 2nd or too low 3rd gear. Also, I'm at 1700 rpm at 60 in 5th!

Back in the day I had an 88 GT that originally had a 2.73 (and a 1500 rpm highway cruise) I had swapped out with a 3.73. 70 mph only shot up to 2100 rpm while every other gear just felt more lively yet also felt more right.

Fun fact: It still pulled 24 mpg highway if I set the cruise at 70.

[Higgybulin]

I am a fan of 3.73's
Higgy

[CraigS]

I'd grab one of the gear ratio/mph calculators and see if the 3.73 will cure your 30ish problem or not. One thing for sure is it will make 1st very short. Start at a light and shifting to 2nd before you cross the intersection short. OTOH, it makes for a very easy car to drive from the light as you can almost just let out the clutch and it will go.

[GoDadGo]

I'm running 3.73's with a 26.1" tall tire and I turn the following at 2,000 RPM:

2,000 RPM...........1st..........2nd...........3rd...... .....4th..........5th...........6th
MPH P/Gear.......15.54........23.13.......32.27........4 1.63......55.51.......83.27

At 6,000 RPM I'm right at 125-MPH in 4th but the RPM's drop to 4,500 RPM in 5th which is a .75 OD and 3,000 RPM in 6th which is a .50 OD ratio.

What is your 5th gear ratio and tire height?

[Jeff Kleiner]

What transmission? If a T5 which one; Mustang spec or T5-Z.

Jeff

[Dave Tabor]

https://www.blocklayer.com/rpm-gear

[MB750]

Well, here's the tag off it:

https://thefactoryfiveforum.com/attachment.php?attachmentid=208240&d=1735591008

And if I decoding that correctly based on a website called BritishV8.org, I've got a T5 WC from a V6 Mustang.

http://www.britishv8.org/Articles/Borg-Warner-T5-ID-Tags.htm

1352-238 Ford Mustang 3.8 V6 WC 3.35 1.93 1.29 1.00 0.72, and reverse is 3.15

According to that chart, based on my donor I should have a 1352-253 with these ratios: 3.35 1.99 1.33 1.00 0.68

There's only two possibilities for this... Either someone took the time to literally change out the tag, or most likely someone blew up the OG tranny and swapped out this one from a V6.

[MB750]

https://www.blocklayer.com/rpm-gear

That's pretty neat. Using my ratios, I'll be at 2650 RPM at 75 mph with my tire diameter. That's kinda high, no?

Honestly I hadn't gotten above 60 yet. I've just been putting around on the local neighborhood roads with occasional blast up to 60 when I pull out onto a 45 zone.

[rich grsc]

If you have under 300hp then 3:73 will be ideal.

[Jeff Kleiner]

Well if you have a V6 T-5 it won't be long until you'll be replacing it anyway ;) but I digress...with a 3.35:1 first gear when coupled to a 3.73 rear as Craig said you'll be pulling second gear before you get across an intersection because the overall is 12.49! Them are stump pullin' gears. When you do blow it up go with a T5-Z which has a 2.95 first resulting in a 11.06:1 first. That's still pretty short and snappy. Actually, after having built cars with a variety of combinations I feel that unless you're dealing with upwards of 450HP something with a 10.2-10.5 overall is ideal.

Jeff

[GoDadGo]

I agree with Sir Jeffski completely and here is why.
Shown below are my ratios for my ZF S6-40 which works well with 3.73's but I've got a 6th gear.
1st-2.68, 2nd-1.80, 3rd-1.29, 4th-1.0, 5th-0.75, 6th-0.50, Reverse-2.50
My first gear at 6,000 RPM equates to is 46.61 MPH and yours is even deeper.

[MB750]

Yea, y'all are right. This isn't a drag car. I do seem to remember having a very short 1st gear in my old 88 Mustang GT as well after I went to 3.73's.

Right now my first is 10.9 total, and I actually like it. I'm gonna leave it for now and maybe just get used to leaving it in a gear a bit longer.

[Redstang69]

I didn't read your build thread so not sure if you're IRS or 8.8 or 9", but FWIW, I'm running a 9" with 3.50 and Z spec T5. I really like the 1st -3rd feel. 1st and 2nd are really snappy, easy to take off and not too short. 5th is great for highway 60-70mph. The 4th/5th I struggle to find the right gear on 40-50mph roads. Running 4th results in slightly high rpms for cruising but 5th results in too low rpms. I'm running the Nitto 555 315 wide tire on 17" wheels. Overall I'm happy with it. I hadn't heard any mention of a 3.50 ratio, but that might not be an option for the rear end you're running.

[MB750]

I didn't read your build thread so not sure if you're IRS or 8.8 or 9", but FWIW, I'm running a 9" with 3.50 and Z spec T5. I really like the 1st -3rd feel. 1st and 2nd are really snappy, easy to take off and not too short. 5th is great for highway 60-70mph. The 4th/5th I struggle to find the right gear on 40-50mph roads. Running 4th results in slightly high rpms for cruising but 5th results in too low rpms. I'm running the Nitto 555 315 wide tire on 17" wheels. Overall I'm happy with it. I hadn't heard any mention of a 3.50 ratio, but that might not be an option for the rear end you're running.

I've got an 8.8 with 3.27's for now, and 25.5" tall tires.

That's one of my worries; trading a weird shift point down low for one up higher. That's why I'm gonna put on some miles before really judging the gears.

[OSU Cowboy]

I've been running a rather high compression 347 - without question the least street-friendly engine I've ever had in any car. 2nd gear at 25 mph; 3rd gear at 30 to 35 mph - can pretty much forget it as it will start bucking like a wild horse at a rodeo. It likes RPM. My solution in town - pick up a little speed and coast in neutral - repeat as needed.

It's backed by a T5 from Levy and 3.55's. Changing gears in the rear would only move the problem a little higher or a little lower. And to be sure ... coasting is much less expensive than changing engines - which might solve one problem with two or three others emerging.

Besides ... it's enjoyment-level on open road is worth a little in-town inconvenience when I'm not in town that often anyway.

[Ford & Jeep Fan]

Yea, y'all are right. This isn't a drag car. I do seem to remember having a very short 1st gear in my old 88 Mustang GT as well after I went to 3.73's.

Right now my first is 10.9 total, and I actually like it. I'm gonna leave it for now and maybe just get used to leaving it in a gear a bit longer.

I too had one of those 88GTs with the 2.73s. I switched it to 3.55 gear. I really loved it. If You used a set of Ford made OEM 3.27 gears and get a Ford made 3.55s

You should Not run into a lot readjusting (re-shimming ) to get the 3.55s set up.

[MB750]

I too had one of those 88GTs with the 2.73s. I switched it to 3.55 gear. I really loved it. If You used a set of Ford made OEM 3.27 gears and get a Ford made 3.55s

You should Not run into a lot readjusting (re-shimming ) to get the 3.55s set up.


The 3.27's in my axle are OEM as manufactured, I'm guessing. That's based on the actual measured ratio (spinning the tires and counting turns), and the little metal tag that was still under one of the cover bolts.

I put a few more miles on it yesterday and I'm getting more used to just not shifting so early and letting it rev out somewhat. Not screaming, but 2200 rpm instead of 1700. It's tolerable.

I'm getting the feeling that I need to make more accommodations to this Cobra than the other way around if I'm to fully enjoy this experience. The oldest vehicle I've ever had any long term experience with was a POS 1985 Cavalier. My first car, back in the mid 90's. At least I seem to have the starting sequence figured out so I'm not cranking for too long and pumping the throttle anymore.

[weendoggy]

The 3.27's in my axle are OEM as manufactured, I'm guessing. That's based on the actual measured ratio (spinning the tires and counting turns), and the little metal tag that was still under one of the cover bolts.

I put a few more miles on it yesterday and I'm getting more used to just not shifting so early and letting it rev out somewhat. Not screaming, but 2200 rpm instead of 1700. It's tolerable.

I'm getting the feeling that I need to make more accommodations to this Cobra than the other way around if I'm to fully enjoy this experience. The oldest vehicle I've ever had any long term experience with was a POS 1985 Cavalier. My first car, back in the mid 90's. At least I seem to have the starting sequence figured out so I'm not cranking for too long and pumping the throttle anymore.

Back in "the day" when the fuss was 3.27 or 3.55 it was a crap shoot, depending on how or what you wanted from the car. Now, think about the car weight at approx. 2300lbs in the same thought. I started with a mild 350HP SBF and 3.27 because those that went 3.55 were complaining of high RPM at cruising speed. Yes, they could burn the heck out of the rears on take-off but paid the price. I liked the 3.27 package and moved to a 430HP SBF and now run a 500HP SBF and it is a lot different than 25yrs ago. Still has grunt, but while others with 3.55's are spinning, I'm off down the road. Now, if it was soley a track car, I'd probably switch to 3.55 to get a better "feel" of the car. However, with the current setup I have, the low end torque outways any gear change. I have 26" tire dia. and a TKO500. It just boils down to your personal preference and what you want to achieve.

[Mike.Bray]

If You used a set of Ford made OEM 3.27 gears and get a Ford made 3.55s

You should Not run into a lot readjusting (re-shimming ) to get the 3.55s set up.

That's correct, when I changed my gears the new ones practically dropped right in.

https://www.imagecoast.com/images/MichaelBray1/4696232144454445619368222853332017181660805n1.jpg

[MB750]

That's correct, when I changed my gears the new ones practically dropped right in.

https://www.imagecoast.com/images/MichaelBray1/4696232144454445619368222853332017181660805n1.jpg



:eek: Mike, please tell me that's a staged pic, or a joke.

[rich grsc]

Excellent job Mike. Do you do transmissions too?

[Mike.Bray]

Excellent job Mike. Do you do transmissions too?

No Rich, just rear ends as that's where I excel.

[StangRacer]

No Rich, just rear ends as that's where I excel.

I am disappointed to hear that Mike ... I was going to see if you would be interested in rebuilding an engine for me. I like your "thinking outside box" to come up with solutions to minor issues!!!

[JCB52]

That's correct, when I changed my gears the new ones practically dropped right in.

https://www.imagecoast.com/images/MichaelBray1/4696232144454445619368222853332017181660805n1.jpg

That made me Actually lol…

[CW_MI]

After joining the forum for research on a build, I immediately though, why is everyone running such tall (?) gearing for a SBF set up. My experience though, is from an old Fox body, set up for drag racing. I ran a 28" tall tire with 4:10's. The car was set up for spray, or I would have had 4:56.
So, I figured, with a mild 347" and a TKX , with a 26" and some change tall tire, 3:73's would be perfect. That drag racing mind is taking over, and old school thinking. So, I might need to rethink this. I don't plan on doing too much highway driving, most of the time the car will be in the 45-50 mph range.

[rich grsc]

These weigh about 1200# less

[PNWTim]

3.73's will definitely make for spirited around town driving.

[Jeff Kleiner]

...so, I figured, with a mild 347" and a TKX , with a 26" and some change tall tire, 3:73's would be perfect...

Depends on which TKX. They're not all the same. Depending on how you plan to use it some will be more compatible with a 3.73 rear than others. So, are you thinking 3.27 first gear or 2.87? How about the fifth gear; .68, or .72 or .81?

Jeff

[GoDadGo]

Question #1
What RPM do you want to turn at 70 MPH?

Question #2
Do you plan to do a lot of Interstate cruising?

Question #3
Is cruising at or around 2,500 RPM okay at 70 MPH?
.75 OD + 3.73 Rear Gear + 26.1" Tire = 70 MPH

Good Luck Gear Picking!

[Ford & Jeep Fan]

Here is a good Gear calculator http://www.grimmjeeper.com/gears.html

[CW_MI]

Depends on which TKX. They're not all the same. Depending on how you plan to use it some will be more compatible with a 3.73 rear than others. So, are you thinking 3.27 first gear or 2.87? How about the fifth gear; .68, or .72 or .81?

Jeff

I did not know there were that many options. I just thought there were only two OD options.
These are great questions....none of which I have answers to. I will probably end up relying on someone that knows much more than I do to guide me in what would be best for me.