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69 Fastback 351W .030 over, mild cam, C4
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Discussion Starter · #1 ·
Just saw listing for several trannys including a couple top loaders. Considering doing a T5 in the future but wondering how much better is a T5 versus a top loader. Maybe if the price is right I just grab one of those?
 

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Define „better“. If you do a lot of highway driving the 5th gear is sweet. Make sure the tranny fits your rear gear, tire size, driving style and engine characteristics.


Sent from my iPhone using Tapatalk
 

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69 Fastback 351W .030 over, mild cam, C4
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Discussion Starter · #3 ·
Reliability for one thing. Driving style also. I currently have 270 open rear but may at some point change that too. Like to stomp it off the line frequently. Also like carving mountain roads in the area I live. Don’t do a lot of top end speed. Engine is 351W .030 over, mild cam.
 

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The differences....

The T5 has an overdrive 5th gear and a lower 1st gear. The 2nd through 4th ratios in the T5 are VERY close to the 2nd through 4th ratios in a wide-ratio TopLoader.

The TopLoader will take gobs of torque and could be found attached to engines like 427 SOHC, Boss429, 428 CobraJet, etc. The T5 without significant modifications, will blow up behind a 351.

If you don't regularly drive over 50 mph or don't mind the maybe 3-4 less highway miles per gallon then I can't see the benefit, other than a bit more ability for a low-power engine to burn rubber from a standing start.
 

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69 Fastback 351W .030 over, mild cam, C4
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Discussion Starter · #5 ·
Woodchuck-I do hit well over 50 frequently but not a lot of cruising above 50. So the top loader will handle my 351 better than a T5? Wasn’t expecting to hear that. I don’t know exactly what the motor is putting out but PO guessed maybe 350hp or so. I may have to give this some serious consideration.
 

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Keep in mind there are several ratios for both
a wide ratio TL is a 2.78 1st gear works well with gears up to 3.50
a close ratio TL is a 2.32 first gear needs at least a 3.50 gear or a 4.11 to have the same starting ratio as a wide with 3.5 but will spin more rpms at highway speeds

The t5 could be a 3.35 1st gear or a 2.95
the od ratio also changes with first gear

I bought the t5z with the 2.95 1st gear and changed the od gear from .63 to .80 with 3.25 gears.
What i wanted was the .72 od with 3.40 gears but the .72 is $350 The .80 was only $80 and i already had the 3.25 gears
I have a 289 that will spin past 6000 but doesn't like to cruise much below 2000.
So i have a starting ratio that works well and cruise at 2050 at 60 MPH


You need to evaluate what you have and how and where you drive
if you have more torque you can pull a higher gear
A 3.35 first gear with 3.5 rear gear you may be shifting before you cross the intersection.

ken
 

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69 Fastback 351W .030 over, mild cam, C4
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Discussion Starter · #8 ·
He has wide and close ratio available. Sounds like I would probably want the wide ratio with a 3.50 rear? Car currently has a C4. Does the cross member have to be changed?
 

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Go wide ratio. Remember tire size when selecting your axle ratio. Gear it for how you intend to drove and you'll be happy. I swapped over from C4 to wide ratio Toploader running the stock 2.80 for a while. Even with a very tired stock 71 302, there was no problem. I even live in a hilly area. Currently I have 3.55's and a different motor. I'm planning on going back to 3.00 limited slip. I have 215/60/15 tires which are about 25.2" in diameter. Once you get past 60 mph it starts to get busy. At 80 mph it's right around 4000 rpm. Depending on what size tire I'd suggest looking in the 3.00 to 3.50 gear depending on tire diameter and maybe staying closer to the 3.00 end since you have a bigger, torquer motor.

T5's are nice transmissions but the problem is they were designed as a compromise transmission. Designed to start off from a stop with tall gears then have a deep overdrive for fuel economy. You end up with a big jump in ratios between 1&2 and another big jump between 4&5. If you go too low or too tall in your rear axle ratio, you end up biasing 4 of the 5 gears to being useful and having a big gap between 2 gears and one gear really not too useful. I see lots of guys that have a production T5 with a 3.35 first gear say how well 5th works with 4.10 gears. They will tell you how short 1st gear is and how quickly they're shifting into 2nd. Or they will tell tou they start off in 2nd. Now here's something very interesting. When you work out the final drive of each gear in a T5 with 4.10 gears using 2nd to 5th gears, the final drive ratio in each of those 4 gears actually works out very close to that of a wide ratio Toploader 4 speed with 3.00 gears!

I've driven the 3.35 T5 with 2.73, 3.08, 3.27 and 3.40 gears. My favorite was the 3.27 followed by 3.40. The 3.27's were ideal as it worked really well with all 5 gears. If you have the Z T5, i think the 3.40 or 3.55 would work very well.
 

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69 Fastback 351W .030 over, mild cam, C4
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Discussion Starter · #10 ·
These numbers get very confusing to me. Math is not my strong suit either. If I want to get good acceleration off the line, smoke the tires some but not blow them completely off, get good acceleration through the gears and not have it screaming on the interstate, be able to carve up mountain roads, what gear do I want with a wide ratio top loader?
 

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Just remember that if you move to a T5 you will probably need a new driveshaft if using the old bellhousing and a spacer. One benefit of any T5 is it is a lot lighter than a toploader. Toploaders are about indestructible with a small block unless you step up to a stroker windsor.

I will give my feedback on gearling. I had a 4.63 ratio with a small block and a toploader. It was great for the quarter but it made it difficult to drive on the highway. When I broke my toploader (not due to power but age I'm sure) I went to a T5Z and the overdrive is great especially with the low rear gears. I can cruise at around 2000 rpms at 55 mph or about 2500 at 70 mph in 5th gear even with 4.56 gears. This is with about a 26.5 to 27 inch tall tire. Shorter tires would increase the rpm. The biggest problem with the T5Z is waiting for it to explode when I install a 347. If it had been available I would have installed the new TKX as it has the same attributes as the T5Z but with much greater torque capacity. Again Toploaders are virtually indestructible with a small block.

As far as shifting it's about the same. The toploaders shift very well with good linkage. I had a competition plus shifter from Hurst and it was great. The overdrive was the issue for me and I would never go back unless I built a much higher torque engine where I didn't need the low gears.

Just my .02 cents.
 

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I believe the tkx in a early mustang requires the welded in cross member under the tunnel to be removed and moved farther back to clear the transmission.

as far as the driveshaft with the t5z it does not need to be shortened just cut off the dust boot on the rear seal or replace the seal with one fot 65 mustang 3 speed same size seal without the dust boot.


ken
 

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I'm a least 350 HP on my 331 with a T5z and all I do is beat the piss out of it on an autocross course. @Woodchuck says that a T5 won't stand up behind a 351. A whole lotta different variations on the T5 over the years to make such a blanket statement because they were in everything Ford and GM over the years from 4 bangers to V8's improving as things went along. Given how I ended up using my car a Top loader would have been fine but I have no plans on replacing it unless it gives me a reason to. If it does blow up I'll replace it with a new TKX because rebuilt stuff tends to stink these days in my many experiences! https://www.tremec.com/menu.php?m=184
 

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1971 Mustang Mach 1 351 C 4 speed
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I'm a least 350 HP on my 331 with a T5z and all I do is beat the piss out of it on an autocross course. @Woodchuck says that a T5 won't stand up behind a 351. A whole lotta different variations on the T5 over the years to make such a blanket statement because they were in everything Ford and GM over the years from 4 bangers to V8's improving as things went along. Given how I ended up using my car a Top loader would have been fine but I have no plans on replacing it unless it gives me a reason to. If it does blow up I'll replace it with a new TKX because rebuilt stuff tends to stink these days in my many experiences! https://www.tremec.com/menu.php?m=184
I had a speed shop in the late 80's to the mid-90's when I sold it. The one thing I used to tell all my Mustang customers is to have at least $1500 in their bank account for when their T5 broke, so that they could get a Ford Motorsports "world class" T5, that they would also eventually break. Eventually we were able to buy the 2.95 "world class" cluster gear kits and repair a lot of them, but after they broke once, they never lasted as long again, consensus back then was that when they broke the cases would stretch and that would limit their durability when they were fixed, how true that is I have no idea. T5's are notoriously weak, the factory torque rating for an OEM T5 behind a mustang, not the 2.3L cylinder one, is 275 FT/LB. We all know that a stock 1987 5.0 made 300 FT/LB. I can still vividly remember one of my best customers who bought a brand new LX 5.0, he broke three T5's in less than 5,000 miles. The guy was an animal, but still. Dealer put in 2 new ones under warranty and told him that the next one would was on him. Selling T5's was an almost weekly thing at the shop.

I bought a Factory Five Cobra kit car about 8 years ago and completely redid the thing. It was a Gen 1 FF roadster so it was built with a donor 1988 5.0 Mustang in 1996. OEM 302 roller engine had 40K miles and the original T5 behind it. I put an X303 cam, Edelbrock aluminum heads with smaller CC's than stock to raise compression, Victor Jr. Intake, 650 DP Holley, MSD distributor, underdrive pullies, new ford motorsport clutch, and 3.73 gears. On it's best day this little 302 could have made 350hp. First time I took it out of the garage and power shifted into 3rd the T5 broke... Next day I was ordering a Ford Motorsport one...

Now, if you do not power shift your T5, you do not drag race your car, and you do not have an engine that makes much power they will last and have tons of advantages over a toploader. First gear being 3.35 or 2.95 is a big advantage, and so is the overdrive, plus less parasitic loses, and a lighter transmission to boot. The one thing that the T5 cannot touch the toploader on is brute strength, a toploader will take a ton of abuse, and keep on trucking, a T5 will not.
 

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I logged over 125,000 miles, mostly highway miles driving cross-country, with my top loader equipped 289 k code and my ‘66 GT-350. The rear end gearings were 3.50:1 in the K code and a 3.89:1 in the Shelby. Those were the factory delivered rear end gearings.

I never had any trouble or worries with the rpm or comfort. The FSB engines thrive on this type of all-day exercise. And so do I.

The top loader is hands down the strongest transmission Ford ever made ,btw, it was designed for the truck line.

if was wanting a different overall gear ratio, I would change the rear end before I’d give up a top loader.

Z
 

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The Toploader is the engineering base for current Nascar Tremtec transmissions and is strong as hell
The T5 is a better shifting trans that will hold about 50 lbs less torque is all
I have replaced so many shift forks and rails on T5's that I will not personally own one
That said I have owned several and will still work on them if provoked
Tons of special tools and real bitchy to overhaul a T5
No special tools and fairly easy to overhaul a Toploader
 

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You will have to look hard to find a T5 actually killed by raw engine power, the threat are the wannabe race drivers. That's why you find people saying a T5 are a weak crap transmission, because they have broken several behind a stock 302", while others are racing them behind fairly powerful engines without problems. A T5 won't handle the abuse from violent shifting like a toploader. FordMuscle dragraced with an early weak T5 in a car on slicks without killing the T5, despite they put enough power to the ground to twist the 28 splines axles in the rear end.
 

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Please understand the tags and what they do or do not mean.

A tag can be moved from one case to another, so interior and exterior inspection is critical.

I have a small block, wide ratio top loader that sports a Boss 9 tag. Somewhere, somehow, a small block guts wound up in the case with a big block tag.

For the T5, a metric boatload of them were used behind 4 cylinder cars and trucks. THAT is not the trans you want behind some beefed up V8 Mustang.

To use a T5 behind a regular V8, it requires either the T5 bell housing or the original bell housing drilled and an adapter plate installed, along with the special trans mount. Also, do you run original Z bar type linkage or clutch cable.

How much is like saying how high.

I bought a bunch of T5 stuff from a place that bellied up. T5 cases, part trans, complete but toast transmissions were stacked everywhere. Complete but bad T5's were $10 to $20 each, grab a stack of them. For some of them, the front bearing retainer was the only valuable part on them, the rest was scrap metal.
 
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