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Old 06-17-2008, 04:01 PM
Walther
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Default T5 Tranny's

I failed to mention that my T-5 consumed 3rd gear during the last session of the drivers school as well. I have no idea how many miles were on it, and it just plain "gave-up". It was "clunking" going into 2nd on Saturday and I thought perhaps I was not pushing the clutch in all the way on down shifts, but... The Engine pulled like a freight train through all the gears, and I had the Carb dialed in, so I was able to finish the session using only 2nd and 4th. ANYWAY....

I am looking at a G-Force T5, @ $2800.00. They offer it in the "legal" gears and rated at 600 ftlbs. Their road race tranny comes with dog eared(?) synchros and such. My next (and cheaper) option is a Tremec.

I considered the T10, but I need the overdrive. At Homestead, I was redlined at 6500 on both straight aways (calculator says 140 mph). Daytona and Sebring are even faster, so I am told.

Is a highly modified T5 legal, provided it has the prescribed gear ratios?
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Old 06-17-2008, 04:23 PM
fairlane_68
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FWIW, I'd go for the Tremec, for reliability. Don't you drive a Camaro? Do the T-5's for the GM's have the same 3rd gear grenade syndrome as the Mustang T-5's? Summit's newest catalog has the Tremec listed for just under $2K, with the right gears.


Just my opinion.
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  #3  
Old 06-17-2008, 04:27 PM
jimwheeler jimwheeler is offline
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Dog rings are expressly forbidden. I might add that the fifth gear on the T5 is a POS. It is an add-on that hangs out the back and really cannot take the torque for very long.
wheel

Last edited by jimwheeler; 06-17-2008 at 04:32 PM.
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  #4  
Old 06-17-2008, 04:27 PM
PRO SYSTEMS
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Default T5

Walther,

Our T-5 is absolutely stock we bought new a year and a half ago from a Ford dealer in the crate.

I don't know how long they last (we were told to carry a spare), so we have our used T5 that came with the car as a spare and our new one is still running fine.

"Easy on the clutch" for engagement is probably the key with these transmissions.

Brad looked at it a few months ago and it looks like brand new inside (not a single chip or mark on any gears). I think I've only missed 3 shifts in the whole year and a half I've been racing. These trannys are so obvious when they are in gear.

So they can last, I think you just have to be sympathetic with them.

We tried to run ours using the overdrive and it did not like that at all.

You could tell it was getting hot as shifting it was slightly harder after 20 minutes of running.

So I think you should stay away from using overdrive and gear it for "4th gear use".

Just our experience.

Patrick James
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  #5  
Old 06-17-2008, 04:48 PM
Ted Johnson Ted Johnson is offline
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This debate always comes back.. Its always been some have no issues with the t5 and some break them every outing. You probably want to read "How to keep your t5 alive" at the top of the technical section if you havent already. In our experience (Wheelers') we went to a t10 transmission and never looked back. If I personally had to run a t5 as we did in years past, I would never have bought my own AS car. I have seen the repair bills Jim incurred for several years.

I think G-Force stands behind their product when you purchase everything from them. Reinforced case and all. But for the price I can have a magnesium case and tail section t-10 thats lighter ? I have to change rear gears, but its the only way to go IMO.
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Old 06-17-2008, 05:00 PM
King Matt
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There are a couple of tricks that can help a T5 live, at least in a lower HP application. I've been using transmissions prepped by Liberty in Michigan. They anneal the gearset to draw down the hardness of the gears, which they say helps prevent chipping teeth and cracking gears from the "ratcheting" effect caused by sticky tires. They also replace the stamped sheetmetal synchro struts with billet aluminum ones that don't get all mangled and hang up the synchro sliders. Everyone has a favorite trans fluid too. I use GM Syncromesh (actually the Pennzoil version, which is the same thing for half the price).

As mentioned, the biggest factor is being gentle with a T5. Missed shifts and wheel hop under braking will kill them no matter how well built they are.

I would use a T10 long before a Tremec. Tremecs shift like ass and weigh a ton.
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Old 06-17-2008, 05:06 PM
jimwheeler jimwheeler is offline
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The gears in the Tremec seem to be too heavy for the kind of racing we do. Like Ted says, we use the T-10 and just change the rear gears. Once you get the Tremec gears spinning, they take a while to slow down for the next shift. At least that's they way it was described to me.
Matt also got it right about how fragile the T-5 is, if you miss a shift, wheel hop, or bounce over a curb at speed, they break. You might get away with it for awhile, but not forever.
Go with the T-10, in my opinion.
wheel

Last edited by jimwheeler; 06-17-2008 at 05:34 PM.
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Old 06-17-2008, 05:41 PM
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jkopp jkopp is offline
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I used the same completely stock T5 four 4 years. It was never out of the car for that time until the RO's last year. I too snagged a new T5 for a spare because of all the doom and gloom about them. I got a great deal on one off eBay right after I bought my car. It went in after the 4 year unit got stuck in 4th at the RO's. I am pretty smooth on it. I think that's why the T5 has worked for me so far. Haven't taken it apart yet to see what's wrong but my guess is shift fork or synchro. Luckily, they are easy to rebuild.
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Old 06-17-2008, 06:55 PM
Walther
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I got the gearbox used, cracked it open when I got it, and all "looked" ok. Despite two spins and a one brake lock-up, I don't remember any eventful incidents all weekend. The third link failure was my poor bracket design.

My only issue with a T10 (as stated) is that my engine, while making a lot of power, does so with a relatively narrow powerband. (3500 to 6800) I opted for a 3.73 rear to use the power. IMO- the car rockets off the corners (until it breaks the gear ) with this set up. But if I am red lined in 4th at Homestead, I can imagine the back stretch at Sebring and the Tri-Oval at Daytona will have me against the rev-limiter with a 1:1 final gear like a T10. I am afraid the car will fall flat on it's face if I change the rear gear.

Scott S. is gonna loan me his World Class T5, which is basically brand new. Now, if I break his loaner, I need to replace it AND STILL get one for myself.

Patrick, I learned years ago that clutch disc compounds are a lot like brake pad compounds, some more agressive than others. This doesn't necessarily have anything to do directly with the clamping force of the pressure plate, although they are related and must work in harmony to get the desired effect. Mine is a very moderate compound with a Cobra pressure plate. Your right, I could have been a little too "enthusiastic" with the shift knob and the left pedal, but I don't think so. I have been thinking about it a lot since you mentioned it. I know an aluminum drive shaft will help as well, but I still have the god-awful heavy stock piece.

G Force has several versions of thier T5. The $2800.00 one I mentioned was their top-of-the-line version, which I just learned is illegal. I know I could put in a T10 and never worry about it again, but then I have to change the final drive gear and probably switch camshafts. More decisions!!

I am trying to do in a relatively short time what you gentlemen have spent years of R&D, trail and error. Based on how the car performed, I knew I made the right decisions right up until the transmission broke
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  #10  
Old 06-17-2008, 07:45 PM
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Walther,

We use a 3.55 gear these days.

At Sebring the 3.73 is faster by over a second a lap from the 3.55, but you are really spinning at the end of the main straight. That where you'll get a lot of wear and tear (extended rpms).

With the 3.55, its easier on the engine and driveline and Second gear is more convenient to use on the short part of the course.

Sure, the 3.73 is faster, but it's an awkward gear (shifts come up in the wrong area...too short or too long) on the short part of the course and took the fun out of driving the car.

But here's where gears will really work for you: According to our computer when we overlay the chunk of the short course we use when we are racing on the Long course and overlay it on a run from this past weekend (short course GPS map). We ran faster on the short course with our old engine combination that would only pull to 6400 (with box stock unported gt40p heads) and 4.30 gears then with our new engine combination (that makes 600 rpm more power) and the milder 3.55 gears. We were faster than our current record with a much less powerful engine package.

But if you think about it...a 4.30 gear is a 20 percent improvement in power over a 3.55 gear...but that tranny will get hot.

So gears are important...they make you go fast, BUT they wear out parts fast via High driveshaft and transmission speeds. They also make your engine run hot (we ran 198-205 all weekend with the 3.55's)

We run the 3.55's, slower, but more practical for what we are doing.

We have a set of 3.73 -3.90-4.10 (New in box) and one set of lightened 4.30 gears for sale that each have only minor race time on them.

Patrick James
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