T5 vs Toploader 4 speed???


May 11, 2016
hey fellas i’m going to swap my c4 for either a t5 or a 4 speed top loader but i’m stuck between the two. I’m currently running 3.55s and as soon as i hit 65 i’m at 3k rpms so highway gas mileage goes out the window and i don’t want to be cruising at 3-4k. What i’m asking is what is more worth my while I drive on the highway a good bit to shows and whatnot and i still want what’s best performance wise too. Also engine is a mildly built 351 windsor with about 420-430 to the wheels with plans for more power so the trans needs to be able to hold up too. Also putting a 9 inch rear with 4.11s in soon but don’t worry too much about that i have more ring and pinions if needed just looking for opinions
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Active Member
Aug 23, 2014
Agree you need the overdrive. If I wanted to run 65mph with 4.11 the toploader wouldn't be an option. Do you already have the 4.11s ?


New Member
Nov 27, 2006
I swapped out the T10 (4 speed) in my 66 for a T5z - best upgrade I could make! I have 3.55 rear end ratio too. I like to DRIVE my cars, not just to the local Cars & Coffee, but I like to take them on weekend trips with my wife. Having overdrive makes it sooooo much more enjoyable on a roadtrip of any kind. Some would say the final drive ratio of a T5z in first gear is too short with a 3.55 rear end, but I like it! I have crisp performance off the line, can "light em up" at will, and still enjoy cruising on the highway.

So the question becomes, how will YOU use your car, or what kind of driving will you do with it? If you do 99.9% of your driving on the street, stick with a street gear, like your current 3.55? With a T5, the 3.55 is probably as steep as you should go to maintain a street car feel. Others will disagree because they are willing to give up some of that street "feel" for an extra tenth or two at the track. It depends on what you want. See if you can find anyone local with similar setups to what you're considering and see if they'll take you for a ride, or even let you try it to see if you like it.

Here's a nifty RPM Calculator so you can see what your engine speed will be based on your transmission and rear end gear ratios.

As far as the T5 options go, you want the T5z. The latest version, the so-called “Z” box that was used in the ’93 Cobra, is equipped with the best of all the updated parts including hardened gears, shortened shifter throws, a bearing collar made of steel, and tapered output-shaft bearings.

Check out MDL for reference to gear ratios on any trans you're considering:

Here's a good article about overall gear ratios which you should read before committing to a 4:11 rear gear:

As for strength, the article above discusses that as well. The T5z is rated at 330 lb-ft of torque capacity, but I know of folks on another forum who have similar HP engines as yours and run the T5z on the track with no issues. The T5 should be able to handle your power level just fine. UNLESS you're merely banging gears and/or drag racing! And if showing off on the street, NEVER rev it up and side-step the clutch! That's just foolish and asking to break things.

One more thought... I'm guessing you want to go drag racing since you mentioned plans for a 9" rear end and 4.11 gears. If you're not drag racing and subjecting your car that that kind of abuse, there's no need for a 9" rear end (and all the extra weight it will add to your car). I was planning to upgrade mine from the 8" to a 9" and the good folks a Currie Entereprises (THE 9" experts!) talked me out of it. They assured me my 8" (they rebuilt the center section) was more than capable of handling 400 HP! An article here states the 8" rear end is is easily good to 300 HP, but talk to the real experts - they know their stuff!
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Advanced Member
Mar 5, 2019
I have a 9 inch 4.11 detroit locker and a T5 w/scatter shielded 289 in my 65. What a great setup, I love it. Of course not to many 'highway' miles in Hawaii.
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Sep 26, 2002
Just a quick note regarding my experience. I replaced my T-10 4-speed with a T5 and it really is fantastic for highway trips. The 5.0 is mild with only 315HP, so the T5 can handle that. I wouldn't push 400HP through a standard T5. As for gears, I am running an Eaton TruTrac with 3.25 gears in an 8". I would highly recommend going to 3.50 gears because you need to drive 80mph to get out of the dreaded 2200 rpm FlowMaster 40 system drone. It's much quieter on the highway at 2500 rpm. My 2 cents.
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