Opinions for rear gears with a T5

stangman67 · Nov 13, 2005

After driving my car all summer, Ive decided that 3.55 is not enough gear for the overdrive. It lugs the motor alot at cruising speeds. So, Im moving to a 9", and which: 3.70, 3.89, or 4.11 would be my most enjoyable choice. Thanks for the input!

69Rcode_Mach1 · Nov 13, 2005

Go with 3.89's they won't be over geared, and you won't worry about the difference in streetability between that and 3.73's because it won't be worth the money to drop down.

180 Out · Nov 13, 2005

I am curious to know what mph you call cruising speed. I have 3.55's and I'm putting in a T-5 so I have a personal interest, if you feel the engine's lugging at 80-85 mph.

iskwezm · Nov 14, 2005

I have 3.80's and i need more due to my cam that is too big and lugs in 5th gear,so im thinking 4.10's or lower

mrfomoco · Nov 14, 2005

I have 4.57's and love them....absolutely love them.

latamud · Nov 14, 2005

I'm running 3.50s and a T-5. I get 18 mpg on the highway. Cruising speed in 5th is 75mph at 2200rpm. On the other hand, my Cuda also has a Ford T-5 and 4.11's in a Ford 9" and cruising speed in 5th gear is 60 mph at about 2500rpm, no tach to confirm. I run the same size tires on both cars, 245/40zr17 and are about 25.7" tall.

ttoney · Nov 14, 2005

What is your first gear ratio? That matters. I noticed that the World class has a pretty steep 1st, as does TKO. Mine is 3.27 and I believe that too low will make 1st gear useless. That would suck also.

steel1212 · Nov 14, 2005

I had my t-5 rebuilt with the 2.93 first gear and 0.63 overdrive gear A.K.A. T-5Z. I have the 4.11s and cruise at around 2400-2500 at 70ish. My speedo doesn't work right now I'm just going by what the calculations have told me and what my buddy told me we where cruising at the last time I went to the strip.

Also go here: http://www.ringpinion.com/content/calculators/RPM.asp

stangman67 · Nov 14, 2005

I spin around 1800 to 2000 on the highway, but at 55-60 i run 1500. Its too low for my engine, so I want to make 5th more usable. Im leaning towards 4.11 for off the line acceleration, but I also dont want to go back to what it was with a c4 and 3.55 on the highway. Since most of my driving is around town, I think i want a strong pull from a stop.

steel1212 · Nov 14, 2005

The only highway my car sees is when I drive to the strip so thats why I went with the 4.11s. Everybody told me that was to much gear but I wouldn't have it any other way. If I come across a spare chunk with lower gears I might pick it up for some long hauls I have planned when the car is done but other than that its 4.11s all the way. Now if you have a turbo like some of the guys here are doing you'll want to go way the other way

latamud · Nov 14, 2005

Tire size makes a difference too.

red65 · Nov 15, 2005

I have 3:55 rear gears, but a higher overdrive ratio in my T-5. I don't remember the ratio exactly, but it's something like 0.8~:1. 80mph nets about 2700RPM, where the engine's perfectly happy. Maybe a different option for you than swapping rear gears?

5.0ina66 · Nov 15, 2005

Your definition of "crusing speed" matters also. I gather that CA people think 85mph is a normal crusing speed, which is not the case everywhere else in the world. In parts of MI, if you aint doing 80, you aint moving. (one of my friends reports having to run 90+ the week after he got his liscence, just to PASS) In the South, 80 is expected as well, but around here, 60-65 is normal.

I'm contemplating 3.89s with a T5, or something close, but I'm going to try to keep it about 2300rpm @ 60, so if I take some trips to the more insane parts of the country, I can set the cruise at 80 and have nice sane revs. I'm interested too, if someone could say what their car spins at 60 & 80, and what gears.
HTH
--kyle

Hack · Nov 15, 2005

I had a 5.0 with the factory 2.73s and I thought that was quite good for the street. edit: I should say this was with a stock, fuel injected 1989 5.0 motor. It was super easy to spin the back tires in first and second. At 75-80 in 5th gear, the magnaflows didn't drone bad. Gas mileage on a long highway trip was over 20. At 55 if you want to pass or accelerate you should not be in overdrive. It's great for cruising though, especially on the interstate.

I would go with 3.23 or so if I could pick anything. Otherwise first gear is useless. Now maybe if you're drag racing with slicks you want a different rear gear, but for the street I think 3.23 or so would be perfect.

70vert · Nov 15, 2005

Thanks, I assume TKO600 has similar ratios

You and I have the same rear gears, so I was wondering what would happen when I did the TKO conversion and left the rear alone for now. I've got the original tired 302, but I want to get everything else rock-solid before that gets replaced. It's good to hear you got such good mileage - with a carbed 302 I'm sure it will be worse but it's good to hear I could actually get some mpg. 2.73 can work, maybe I'll actually be able to use 1st.

Hack said:
I had a 5.0 with the factory 2.73s and I thought that was quite good for the street. edit: I should say this was with a stock, fuel injected 1989 5.0 motor. It was super easy to spin the back tires in first and second. At 75-80 in 5th gear, the magnaflows didn't drone bad. Gas mileage on a long highway trip was over 20. At 55 if you want to pass or accelerate you should not be in overdrive. It's great for cruising though, especially on the interstate.

I would go with 3.23 or so if I could pick anything. Otherwise first gear is useless. Now maybe if you're drag racing with slicks you want a different rear gear, but for the street I think 3.23 or so would be perfect.

Edbert · Nov 15, 2005

The Fox/SN95 guys are very fond of their 4.11s, and their cars are generally heavier than the early cars. I can see the 3.50s lugging at 60mph but at 80 they should be fine, really depends on your induction (valve sizes and cam profile) though. I put 3.89 behind my AOD (overdrive ratio is the same), seemed like a great compromise for street and strip to me.

65up2d8 · Nov 16, 2005

In researching something for another thread tonight, I stumbled upon the following on this topic, which seems to be quite logical to me: http://www.dbperformance.biz/askdb.htm#q1
Keep in mind, however, that our cars are somewhat lighter than the late models the article is speaking to, which would, of course, dictate a slightly higher gear for our classics.

Edbert · Nov 16, 2005

Quoted from the article above:

A 4.10 may sound extremely steep, but because the AOD's 1st gear is so high (numerically low) and 4th gear (overdrive) is steeper than the T-5 it's a very good choice for the driver interested in making their car perform better.

They are right about the steeper 1st gear of the AOD versus the T5, but the two OD gears are 0.66 and 0.67. Calculate that out and they are essentially the same, the RPM difference at 60MPH is so small that most tachs cannot even show it.

180 Out · Nov 16, 2005

Just to add the two cents that the 1st gear ratio of commonly available OE "world class" T-5's might leave you unhappy with anything higher than a 3.73, here are the gear ratios for some common "World Class" T-5s:

1352-202 79-93 Aftermarket 2.95 1.94 1.34 1.00 0.80
1352-169 86-89 Mustang 5.0 3.35 1.93 1.29 1.00 0.68
1352-199 90-91 Mustang 5.0 3.35 1.99 1.33 1.00 0.68
1352-208 92-93 Mustang 5.0 3.35 1.99 1.33 1.00 0.68
1352-219 94 Mustang 5.0 3.35 1.99 1.33 1.00 0.68
1352-246 94-95 Mustang 5.0 3.35 1.99 1.33 1.00 0.68

Source: http://www.fordmuscle.com/archives/2000/09/t5swap/index2.shtml

The "1352" number is stamped on a tag that's stuck under one of the tail housing bolts.

You'll notice that 4th gear in the T-5 is exactly the same as 4th gear in a toploader, or 3rd gear in a 3.03, a C-4, or a C-6. So if you're lugging at 55 mph in 5th, running in 4th gear will be no different than they way 100 million cars ran in the old days.

HistoricMustang · Nov 16, 2005

3.89's in mine.

But, it you are going to do much of the street stuff drop back to 3.55's........

HistoricMustang
www.historicmustang.com

Opinions for rear gears with a T5

stangman67

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