I seem to remember that the best T5 could handle just shy of 300ft-lbs. Do I have that right? Is there some master T5 out there I'm missing, or do you need to go to a tr3550 or something else to get away with over 300? I'd be looking to bolt it to a SBF bolt pattern, and pay Challenge prices.
I belive that would be the World Class T5 that came in some Mustangs. Should already be SBF pattern.
I clicked on this post expecting this:
Ford Motorsport T5z is the only one rated over 300, and it is still only 330ftlbs.
An aftermarket countershaft support is probably the best bang for the buck to help a T5 live longer at Challenge prices.
A lot depends on the intended purpose of the car. Daily driver, autocross, road course, or sticky tires and a hard launch at the strip?
https://www.gforcetransmissions.com/tran_gt-5.asp
Not challenge priced, but can handle more than that.
They SAY 300ish... but they're are lots and lots of cars out there with more. I'd assume some are more of a ticking time bomb than others, and how you treat it (dragstrip launches, etc,) will have an effect on it, but it won't instantly explode with considerably more HP/torque.
In reply to Floating Doc (Forum Supporter) :
I'm not really a drag strip guy, DD and autocross would probably be it. Maybe get into some HPDE? That would be after the Challenge, though and at that point I wouldn't mind upgrading if need be
The torque ratings are based on first gear strength and a transmission that won't need undue warranty claims in 100,000 miles of life, correct?
I had the "Cobra" version in my 1993 Cobra Mustang. I believe that trans was rated at 325 fl/lbs. I road raced it and I did end up breaking 3rd gear but then I was beating on it all of the time. I raced it from 1995-2006 when I sold it.
From what I know from my more recent experience is that the T5 will live as long as your are kind to it. I've seen T5's not last a day in a Lemons race car that's driven by 4-5 different drivers of various shifting skills. I've seen a Lemons team install a G-Force gear set in their T5 and have that break too!
What I've found is you do not use the trans as a brake! That is make smooth down shifts and use the cars brakes to slow down and not the trans/engine.
I've rebuilt 6-8 of these trans and they work great behind a 4 or 6 cyl. engine and they will live behind a small V8 if not abused.
1st gear is generally the hardest gear on any trans, because of the multiplication involved. So if you don't plan to hammer it in first that is already upping the safety factor. But with a t5 you also have to be careful of the 3-4-5 shifts because of weak synchros. Yes, all this stuff can be improved. And if you buy a cheap core and rebuilt it with good parts, i'd be interested in watching.
However, I'm not a fan of the t5. if you have to baby your car everywhere and be constantly worried about the trans, whats the point?
If I do another SBF car on a challenge budget, I'll probably go for an auto.
There are a lot of T5-equipped Fox body Mustangs making a lot more than 300 lb-ft, but Ford decided the T5 wasn't strong enough to live in the Supercoupe (early ones made 315 lb-ft).
I imagine a lot of it depends on the usage, as stated above, along with vehicle weight, etc. Supercoupes are a lot heavier than a Fox Mustang.
Torkel said:I clicked on this post expecting this:
How about both?
I suspect it has a lot to do with the weight of the vehicle being pushed around. 5.0/T-5 in a Miata should be fine for a long long time. In a 3/4 ton truck pulling a trailer? Probably not so long.
In the 1800 lb Zoomboni? I expect it to last forever.
No clue how much weight will be in front of this trans, one of those body swap abominations that GRM loves so much
matthewmcl (Forum Supporter) said:The torque ratings are based on first gear strength and a transmission that won't need undue warranty claims in 100,000 miles of life, correct?
Yes, and sort of.
Yes it is based on first gear strength, but the taller first gears come by courtesy of a taller transfer gear, which puts a lot less stress on the countershaft. So in a way the first gear thing is partially a cause and partially an effect.
And people were breaking T5s with stock Mustangs at the drag strip if they had traction, so that torque rating does come with an asterisk. (Third gear was more likely to fail, anyway, because that end of the mainshaft isn't supported by anything but a little needle bearing in the input shaft)
I've road raced with weak gearboxes and never had a bit of problem. Just don't dump the clutch on hot sticky tires unless it's off the track on grass or something. Give a 1/10th of a second so the gear can get fully in place before throwing full power to it.
You can have a lot of fun and do pretty well just by being a little bit careful. Remember the race can't be won at the starting line but sure can be lost.
Old Muncie gearboxes used to try to spred the case apart. It got worse as the case front would wear and the gears had a head start. Then even the vaunted M22 Rock crusher would spred it's case and start spitting out gears.
If you have no mechanical sympathy and can't feel a gearbox going, buy the expensive racing gearboxes with dog ring gears and tough cases.
Street gearboxes with their slow shifting syncros need a deft touch to survive. But any clod can Ruin one.
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