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Opinions please. Is it worth the money and time to

2K views 16 replies 15 participants last post by  CJM68GT390 
#1 ·
replace a 4-speed top loader transmission with a mid 90’s t-5? I am thinking about doing this in my 67. How difficult a swap is this? What other parts will I need? Thoughts.
 
#3 · (Edited)
Do you drive your Mustang a lot? If you do, then I do think it's worthwhile to install an overdrive.

If you don't drive your Mustang a lot, then no. It's not really worth it.

I spent a lot of money, time and effort installing a TKO-600 in my Mustang. I wondered if it was worthwhile. Last I week I drove the car to Steamboat Springs for the Mustang roundup; about 5 hours each way. Oh, good golly, it was so worth it! I have a 3.70 rear gear. In overdrive, I can breathe on the gas pedal and the car does 70 MPH. As long as I keep the RPMs at or above 2,000, the car will effortlessly cruise; even up steep inclines like I-70 through Vail Pass.

On the way to Steamboat, I stopped in Silverthorne, which is about half way, to gas up. The car took 9 gallons. I got to Steamboat and still had half a tank. Thus, I could have made the whole trip on one tank of gas (22 gallon tank). Yeah, I know. A lot of people say, "Who cares about MPG?". But again, if you drive your Mustang a lot, it does matter. It's no fun spending $50 or more to fill the tank, but it downright sucks when you have to do it constantly. An overdrive also significantly reduces wear on the engine.

Now, whether or not a T-5 is the best option may be debatable. If it's in your budget, a TKO would be better. You'd have a lot more room for future engine mods. Although, many people have put many miles on a T-5 with pretty potent engines. Your car, your choice.

FYI, if you're thinking you can find a good, mid-90s T-5 at a local salvage yard and bolt it in, think again. You might get lucky, but pretty much any used T-5 you find it going to be completely shot. If you can rebuild it yourself, cool. By the time you pay someone to rebuild it, you might as well buy a new T-5. You will need an adapter/spacer and a new trans cross member. You might have to shorten the drive shaft. You can use the factory, Z-bar clutch linkage. That's what I did and I'm perfectly happy with it. (I did install a rollerized clutch linkage.)

That's my take anyway.
 
#4 ·
Depends,

  1. What engine do you have, or plan to have, in the future?
  2. Do you do a lot of highway driving?
  3. What is your rear drive ratio?

I upgraded to a t5z (a stronger version of the the t5, but physically identical) and love it. With my mufflers and 3.89 gears, highway driving would be unbearable without the overdrive.

-Shannon
 
#6 ·
What gears in the rear axle? If it’s the typical 2.79 or 3.00 you’ll end up having to swap those for something lower because the engine probably won’t like lugging along at 1200 rpm in overdrive....
If you’ve got 3.55 or lower (higher numerically) then I think it’s a good idea.
The Ford toploader is one of the best transmissions out there, but I still swapped mine out for a 5 speed and it was one of the best mods I’ve done. I have 3.91 gears though, 3500+ rpm on the freeway to keep up with traffic got old after 20 years.......
 
#7 · (Edited)
The toploader's a 4 speed with reasonably close gears. That means you will essentially be able to choose between outstanding acceleration (think drag racing) or gear down for economy highway use, which will give up some of your off-the-line performance. If you can make tire smoke in 1st anyway, the amount of 'performance' being lost due to using highway gears is questionable. It is well-known for its ability to take hard use. If you want to bangshift and drive your car like you stole it, you'd be hard-pressed to find a better transmission.


The T5 comes in several flavors. Many of them have a very low first gear, and wider gear spacing. If you have an engine built for mild street, with a wide powerband, this is not a problem! If your engine is peakier, the bog you will get shifting between gears can be problematic. Most T5's will not stand up to full-throttle bangshifting behind a healthy engine, with sticky tires. You'll make horrible noises and spit parts out on the 1-2 shift, eventually. If you can limit yourself to more moderate use, letting off on the gas and using the clutch gently between shifts, it should last a long, long time. You also get the benefit of an overdrive gear, so you can have good acceleration off-the-line and still spin the engine at modest speeds for highway use. Probably the best version you will find for performance use is the T5 "Z".


Even a Toploader can be broken with enough abuse, but there's a reason that even Chevy guys know the name. If you've got one, don't give it up on a whim!
 
#11 ·
Like others have said, it all depends on what kind of driving you plan to do. If its just a weekend cruiser around town, stick with the 4 spd, if you plan to take it on long drives, the 5 spd is the way to go. I had a 4 spd toploader in my 69 Mach 1 for 27 years, did a couple 2-300 mile trips in it every year and it was fine. Decided to swap in a T5 just before heading to Charlotte (1400 mi round trip) for the 50th. Single best mod I have ever done. I have taken the car on several 1000-1500 mile trips and it performs flawlessly. Great gas mileage, much, much quieter, can cruise 75 turning 2100 rpms. I even added a modern radio because you can actually hear it now.

Its a very easy install since you already have all the pedals and linkage. Couple mods to the toploader bell, buy an adapter plate and maybe shorten the driveshaft (I just had a new one made for $200).
 
#12 ·
I drive the car a LOT. The T5Z with the better first gear is great through 1-4 around town. Shifts nicer than a top loader, is lighter, has better availability of parts etc. 5th gear on the freeway at 2100rpm and 75mph with 3.55's in the back is awesome on road trips.

Mine makes 400hp and so far is surviving behind it. The known issues are bent shift forks from slamming gears too hard and big launches at the drag strip with traction and a few other things of that nature. Behind a mild 289 or 302? Its hard to beat for the cost.

I may go to a TKO in the future if it does fail like certain people keep claiming it will.
 
#13 ·
The production T5 is not a bad transmission but it is a compromise transmission. It’s gear spacing is very wide intended to start off from a stop with tall gears and provide fuel economy over everything else in 5th. You have a BIG gap between 1&2 and 4&5. You have to watch your rear gear selection otherwise you bias 4 of the 5 gears to the axle ratio and out of those 4, not evenly spaced. I’ve driven 3.35 1st gear T5’s with 2.73, 3.08, 3.27 and 3.40 gears. My favorite was the 3.27’s. These used all 5 gears the best I thought. The 3.40’s would be my next choice.

On my 66 I have a wide ratio Toploader with 2.8’s. I actually like this set up very much, the 3.0’s that Ford used with the wide ratio Toploader I think would be very good set up. I like in a hilly area and I have no issues with the 2.8’s. Great gearing on the highway too. Tall enough for good cruising and low enough that I don’t have to downshift on every incline to keep pace. Other advantages you’ll keep the driveshaft speed down, cooler running rear axle, less friction and heat. Not to mention very good drive line angle.
 
#14 ·
The production T5 is not a bad transmission but it is a compromise transmission. It’s gear spacing is very wide intended to start off from a stop with tall gears and provide fuel economy over everything else in 5th. You have a BIG gap between 1&2 and 4&5. You have to watch your rear gear selection otherwise you bias 4 of the 5 gears to the axle ratio and out of those 4, not evenly spaced. I’ve driven 3.35 1st gear T5’s with 2.73, 3.08, 3.27 and 3.40 gears. My favorite was the 3.27’s. These used all 5 gears the best I thought. The 3.40’s would be my next choice.
Well, if you're talking about the 3.35 first I agree, most here are referring to the T5Z with a 2.95 first. It has a pretty good gear spread, similar to the other 5 speed options.
 
#17 ·
Ditto to what the others have said.
My ‘68 390 had a wide ratio top-loader with 3.50. I was going to replace the 3.50 with a 2.80 as the 390 has so much torque I could easily start in 2nd gear and driving at 70 mph with a big block turning 3,500 is not fun. But the top-loader was really busted-up with a mounting ear broken off and the front bearing retainer welded together! It needed a full rebuild and then some. So, I installed a TKO-600 and the first time I took it out on the highway I was stunned how quiet the car became.
 
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