Tranny first gear combined with rear gear help

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mshred

mshred

The Green Manalishi
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hey guys,

i just picked up a t5 out of a 90 mustang to use in my 71 scamp. The beauty of the overdrive will be awesome since this will be primarily a street car, but my question concerns performance. The car will have a 340 and the rear is an 8-3/4 suregrip that will be set up with 3.91 gears that i got at a great deal. The first gear ratio of the T5 is 3.35, and im wondering now if im going to have traction problems and be blowing up in smoke every time i step on it off the light...I have a buddy with a mustang II that has a 302, 4.64 gears and the same T5 as me and he says he has no traction problems of that sort, and i see lots of guys with mustangs running 4.30's with their t5's...what do you guys think? I am I okay with 3.91? should i go to a higher numerical ratio or a lower one? If i could go higher i would love it since id have a ton of giddyup and that overdrive to cruise at low rpms....lets hear what you guys have to say on this as im all ears8)
 
Well, your 340 will probably make more power than their 302's, and if you have good rubber in the back I'd be more concerned with hurting the transmission from the torque. I've heard the T5's can't handle too much compared to, say, the TKO's. Just make sure you have good rubber and a good suspension setup and you should be fine.
 
the car is minitubbed and will be running 350/50/15 et drag radials...I know my car makes more power than a stock 302, but my buds mustang II is faster than my car....I know everyone says T5's cant handle power and such, but they can as proven by the 5.0 mustang crowd (many of whom have stock t5's living behind 500hp)...The more traction i get the more parts i will break, but we'll just have to see what happens...im more concerned about what i asked in my original question on the combination of the gearing in the tranny and the rear
 
also suspension is just going to be pinion snubber with either heavy duty leaf springs or maybe some super stocks (if i have the cash)...dont know if that would make much of a difference on whether the car gets traction or not and whether or not ill be spinning tires or hooking and going hard
 
is there a basic formula to calculate what size first gear will be with first gear ratio and rear end ratio?
 
If you're asking what I think you're asking about the gear ratios...you just multiply them.

A 3.08 first gear & a 3.91 rear axle gear combine to make 12.04. Is that what you're asking?
 
yes thats what im asking...but what im also asking is would the final number from multiplying those two numbers give me traction and performance problems? so i would multiply 3.35 and 3.91...i come up with 13.09....sounds kinda like a big number...i just want to know if that number is going to give me problems
 
I'm gonna say it won't be an issue with those gigantic meats. Put it in and give it a shot, if it turns out to be an uncontrollable sidewinder (which I highly doubt) then just swap out the rear gears.
 
well since i havent been gettin to much input on this, im just going to hope for the best now and like you said see how it goes
 
The 3.91's Will Probably Work Out Ok But 4.10 Or 4.30's Would Be Better For Quicker Et's--definitely Use Ss Springs--better[longer ]shocks[rear] Or Adjustable Shocks, Adjustable Pinion Snubber, And Looser Or Adjustable Shocks On Front Wouldnt Hurt Either, Car Will Launch Better/straighter With Frame Rail Connectors[preferably Welded In] Have Worry About Tranny Holding Up Over Time, 340 Will Have More Torque Than 302 Hence The Future Problem, But Hell, Give It A Shot And Blow The Sheot Out Of Them Frauds[foorrdds]
 
It depends on chassis.

The T-5 was available with 3.35 and 2.92 first gear in the Mustang.

On the street, I always found the 3.35 to be a bit of a granny gear. With any rear cog to speak of, you would be shifting to second at 5mph or so.

However, it is worth ET at the track.

The OD with a stock T-5 is only a .68 ratio, so I'd stick with the 3.91s. It'll make highway driving more pleasant, and you won't give up too much at the track.

As far as stock T-5s holding up behind 500hp. Well, maybe. In my experience, the only stock T-5 that would have a chance of doing that for very long would be a World Class, which yours isn't, and one of those would take it, but not for very long. There are aftermarket gearsets (G-Force and others) that will hold that kind of horsepower for years though, and a T-5 shifts way better than a TKO.

the most important thing for making a tranny live is getting a good clutch. You don't want (or need) some hard hitting ridiculous thing, especially with a drag radial tire. Mcleod makes several good units these days.

Also important is some good synthetic fluid with anti-clash additives like Royal Purple Synchromax or Red Line ML.

These guys: www.promotionpowertrain.com built me a lot of nice stuff when I was racing Mustangs, and they know their way around a T-5.

They usually have some good rebuilt stuff for reasonable pricing also. You could get a world class unit with the highly awesome .59 OD ratio for pretty cheap (you have to ask for the good OD). In a Mustang, I ran that ratio with a 4.30 gear and at 70 mph, I wasn't even hitting 2500 RPM with a 26" tall tire.

Good Luck

Steve
 
hey guys thanks for the advice,

first off my tranny is a world class, its the higher rater one besides the z spec rated at 300ft/lbs...its from a 90 mustang and its made by borg warner, not ford...a new clutch kit will definatly be in the works for it...my car wont have 500hp right now so when it goes it goes, but i dont expect it to happen soon...when it does i plan on upgrading with the g force stuff or something more econmical from astro performance...my car has a snubber, will have stiffer springs, and it will have subframe connectors as well...what do you mean when you say granny gear? is that good or bad thing? sometimes i wonder if i should go with a 4.56 gear now, as i could still cruise at around 2500 with 28 inch tall tire i plan on running
 
mshred said:
hey guys thanks for the advice,

first off my tranny is a world class, its the higher rater one besides the z spec rated at 300ft/lbs...its from a 90 mustang and its made by borg warner, not ford...a new clutch kit will definatly be in the works for it...my car wont have 500hp right now so when it goes it goes, but i dont expect it to happen soon...when it does i plan on upgrading with the g force stuff or something more econmical from astro performance...my car has a snubber, will have stiffer springs, and it will have subframe connectors as well...what do you mean when you say granny gear? is that good or bad thing? sometimes i wonder if i should go with a 4.56 gear now, as i could still cruise at around 2500 with 28 inch tall tire i plan on running
Click to expand...

A granny gear is like the first gear in a diesel truck. Lots of RPMs, no mph.

All of the T-5s were made by Borg Warner, until they were made by Tremec.

How high does your 340 spin? 4.56 is a lot of gear, unless you're able to make power to 6500 or so.
 
Hey LXguy,

i knew they were made by borg until tremec took over, just stating it for rbguy who thought it was ford stuff...my 340 will probably spin to about 6000 or so give or take a little...I wouldnt be changing the gear anytime soon since i just bought these 3.91's but sometime in the future i could forsee maybe even going up to 4.30's. Would a granny gear be good or bad for the track? i mean it obviously sounds like i wont be in first gear too long? or is it the other way around? Im down for whatever will make me go faster, since with that 5th gear overdrive i can still get good mileage....if granny gearing is good for speed, then i like it =)
 
What you should do is put in a gear that lets you go through the traps at say around 5500-6000 RPM in 4th gear. And use 5th gear to get to and from the track.
 
Hanlon and D&D transmissions sell stuff for the t-5 as well. Theres a g-force gearset for the t-5 thats still synchronized and can supposedly take 600hp and 500ft lbs (if you use their mainshaft as well)of torque without all the extra weight of the tremec tko 500/600(they dont like to shift if your really zinging) When I was into foxbodies I had a 347 and a t-5 w/3.73s and I blew the tranny a cpl times in the 3yrs I had that engine in the car (t-5z) with alot of passes on sticky tires (low 12s,high11s w/ 1.6 60fts) Get a good shifter for it like a steeda tri axe or a pro 5.0 shifter. I have a friend with a gt ragtop mustang street car runs 10.0s with the tremec tko600 and he had it faceplated in 2nd and third to make it shift right for him when racing, isnt really a mod for a regularly driven street car but it works.
Good luck.
Marvin
 
hey guys,

thanks for the advice...havent calculated what gear or rpm i will be going through the traps yet....does make sense to want to be in fourth though since shifting to 5th overdrive gives a prety big drop in rpm's...In regards to the TKO, i hear about too many problems with those trannys to want one right now...id rather build a g force t5 if mine breaks on me (mind you the g force stuff costs almost as much as a tko)...im just going to have to see what happens with the t5 reliability wise....im going to just stick with the 3.91's for now and see how that goes...i still have 3.23's to use if i want to go with a lower numerical ratio
 
You'll like the g-force upgrade, it shifts well too. I've never owned one but got to make a few passes in a stang that had the g-force guts in the t-5, shifted really nice.
Marvin
 
cool....now just gotta wait for the tranny to blow up and save up 1,500 bucks to repair it lol
 
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