I'm about to drag my iroc vert out of mothballs and get her up (hopefully) in time for summer. When I put her away, the T5 was developing a habit of jumping out of 5th, a condition which I'm sure hasn't gotten better while in storage. Rebuilding the trans is the plan.

I see that G-force is selling a 600hp capable T-5 Kit for about $1000. Options add more, but it still comes up under $2000.

This looks pretty good to me if it means I can quit worrying about breaking the trans.

Anybody believe the 600hp hype, or have any experience with this kit, or have any fact based opinion on it?

 

I would prefer if they gave a torque rating on it. An engine making 600 hp at 8000 rpm doesn't make a ton of trans breaking torque.

 

Right. They're very careful about the words used in the claim, but they suggest that it'll live in a 3300 lb car with 600hp and drag radials at the track. That's way more than I'll ever put on it with BFG comp2s on the street or when autox-ing.

 

Unless that kit comes with a new case that's been reinforced somehow against stretching like the stock case does , no , I can not believe 600 HP .

 

It doesnt....friend had one and broke it at that power level or slightly less. Drag races alot and it couldnt handle it. Street car may be fine

 

They do sell a new stronger case but I am not sure if this kit comes with it.

 

I didn't see any mention of they're super case on the website. I know they used to claim that most of the problems with the T5 was the flexible case. Maybe that's because they were selling upgraded cases at the time. Now they're selling gears, so it's a gear problem.?...

 

Straight cut gears will aid the case flex issues but the case is still the main problem
Hanlon used to have a billet case, but I still would not trust it too much

 

Jegs listing says the gearset can handle 500lbs torque. I wonder if that means that the trans would take 500#, or that the gears, set up in some sort of hardened steel fixture can take 500#. Yes, I'm skeptical. I'm going to call.

 

https://www.astroperformance.com/

Doesn't show a GM kit on the website but they have one. I would go this route before a G force

 

I have no interest in a "600 hp" T5 when a properly stock built V8 version (assuming someone who can drive) will suit a 350.

I would be interested in flex thresholds of a stock case with fixed front bearing openings vs. a G-force case or Hanlon's billet case. I have a V8 third gen 1988-1992 case and the openings are about +0.0015" "longer" than they are "wide." Machine work to correct something so small vs. buying a new G-force case is a good question!

I get skeptical of gearset upgrades. If the mainshaft pilot bearing setup (loose rollers in the maindrive in most T5s) isn't holding the mainshaft very well, it could explain the 3rd gear reputation. That doesn't mean the gear is at fault. It also doesn't mean a new gearset is going to fix anything. I would like to see how a tapered roller mainshaft pilot bearing setup stands a "missed" 3rd gear shift.

 

Jmd, have you ran or broken a G force or astro t5 or are you just repeating the same bullshit about t5's that everyone else repeats?
Funny how people who have never ran one tend to offer an opion

 

subd

 

Even with the gears and case you'll still break them if you have 600 hp and drive it hard. This was a capri svo turbo 2.3 making 500 whp and running 10.6-11.0's with 1.4 60 foots on slicks

Top pic is the first time it broke and bottom was another breakage last season. He keeps 2 transmissions on hand so has a spare to keep driving

For the money get a built t56

 

The G-force gears are 600hp capable in the same way that stock T5 gears are 500hp capable...people have gotten that much thru them at the track.

The clutch is the key component that can make that happen. Coupled with the right clutch, anyone here with a typical sbc can get similar results, regardless of weight/tire/hook.

 

you mean a clutch that starts slipping early and let's go at say 400lbft?

 

A clutch with a yield point around 600 ft/lbs would be a good match to the G-force gears and stock T5 case. Basically if you use the clutch to smooth out torque spikes, you will be able to get more average power thru a transmission before exceeding it's failure point.

I’m using general numbers here, hopefully to make this concept easier to understand….
…Lets say a generic 450ft/lb@4500 engine is tested for how fast it can accelerate WOT with the clutch pushed in, no load applied. Acceleration rate is found to be 8500rpm/second thru the heart of it’s torque band. At this rate, the engine gains roughly 2000rpm in .235 seconds.
…Now the car is launched 5500 WOT and .235 seconds later, the engine loses 2000rpm before the clutch begins to lock up. If it took 450ft/lbs to accelerate the engine’s inertia 2000rpm in .235 seconds, it also took 450ft/lbs to remove 2000rpm from that launch rpm in the same .235 second time period. Where did this additional 450ft/lbs of inertia energy discharged over .235 seconds go? Into the transmission’s input shaft along side the engine’s WOT 450ft/lbs. That’s a total of 900ft/lbs for a brief .235 second time period, then torque drops below 450ft/lbs as the engine starts gaining rpm and some of it’s 450ft/lb output is siphoned off as energy being recharged as inertia back into the rotating assembly.

From there you can play with the rate of the rpm loss and how that effects the intensity of the torque spike that the input shaft will see. To remove 2000rpm from the rotating assembly over twice the period of time requires ½ the torque, so doubling the duration of clutch slippage to .47 seconds will cut that torque spike in ½ to 225ft/lbs. In this instance, the input shaft will see 675ft/lbs for .47 seconds before dropping below 450ftllbs.

As you know real life power application isn’t binary like my example, but I hope this helps illustrate where I’m coming from.

 

Yeah, I get it, its tedious when you operate near the limit.
I just want to be able to beat on my 200hp 305/T5 camaro with stock clutch and comp2s on dry pavement without doing a bunch of math or worrying about the trans giving me problems. Seems like that should be pretty easy, but maybe not so much with oem style equipment.
I told g force and astro the same thing via email, and neither has responded so far.

 

The shop that rebuilt my T5 asked some very careful questions, and concluded since I wasn't really interested in hammering the car hard on a regular basis, nor racing, my T5 would likely live many years without issue behind my L98. It was worth the drive to Atlanta to take the transmission to him when my son destroyed the reverse slider gear, and the cluster gear accidently.

 

It just isn't that simple at all to place a meaningful rating on a transmission, as the engine torque is only part of the equation. G-force chose to go the 600hp capable route as there is indisputable evidence that their gearsets have survived passes that required 600hp to achieve. Can anyone get 600hp thru their gearsets? Your mileage may vary, as the wrong clutch can turn a wimpy engine into a violent monster at the input shaft.

 

I have upgraded customer's transmissions with G Force parts. I have removed broken G Force parts and replaced with OEM parts too. So I'm a repeat customer.

(One of the) T5 in my garage is an example of one with some case stretch. It was behind a 408. It didn't fail the gearset; it came out for other shifting issues. Sometimes neato parts don't address the true issue of failure. A G-force mainshaft won't help when wheel-hop shatters a C5 T56. Their gears don't help with a lubrication issue at the headset gears in a T56. Those are examples I've fixed.

You might find the context of my third paragraph interesting in light of the third gear a couple posts below yours. I hope you understand why.

 

Oh no... not screen door closers in the linkage again....

There's acoupla issues with "handle the power". OK fine, the mfr says "it'll handle 600 HP". Great. Just exactly what does that mean?

Does it mean:

If you apply 600.000001 HP, the matter will meet the anti-matter and annihilate the entire known universe in a supermassive black hole? (probably not, we can only hope)

If you apply 600 HP to 100 identical ones, 95 of em won't scatter into shrapnel the first time, and 5% will still not be shrapnel after 10 times? (hmmmm.......)

If you apply 600 HP to YOURS, it won't grenade? (doubtful)

If your motor is capable of 600 HP but you (a) keep your foot off the gas so that it never puts out more than 350 HP, or (b) put a screen door closer in your clutch linkage so that the other 250 HP dissipates into heat and burnt clutches, that it will survive ONCE? twice? ten times? ??? (or does that depend on where you slide the little slidey thing on the screen door closer piston?)

Does it mean that if you can PROVE your motor's peak HP is less than 600, that the 100% replacement no-questions-asked lifetime warranty including 2-way freight and installation will be honored on the spot in case of ANY failure? (now we're in fantasy land)

Or what?

Just EXACTLY what are they saying here?

Tell us THAT, and I'll tell YOU whether to laugh, cry, run away, or sue. Or buy it. I'll only charge you $1000 for the privilege.

Yeah right.

I PERSONALLY knew someone who was out skydiving one day, and their parachute did not deploy at the moment of truth. Yet, they survived. Does that mean that EVERYONE should skydive without a parachute? That I should go get on the skydiving boards and tell everybody to leave their parachutes at home? That's what you just said. Don't deny it.

Don't futz around with a T-5. By the time you give those g00bs your money and install their stuff, you've ALREADY got more $$$ in it than you would just going to the junkyard and getting a transmission that can ACTUALLY handle V8 power levels. If you're not racing in a sanctioned class of formal racing where the T-5 is required but unlimited modifications to it are allowed as long as it retains some form of identifiable T-5 features such as the 88mm gear spacing, then that stuff is NOT FOR YOU.

 

, there's your problem right there...when your T5 case has 88mm spacing, you really should check it for cracks!

 

Even with the occasional typo , I'd go with Sofa's info before I'd believe one single word from your keyboard .

And why is that , you may ask ?

Simple . Because Sofa is here for nothing more than his love of these cars . His knowledge base regarding them spans the entire 34 or 35 years of their existence . And he likes to dispel BS in a humorously sarcastic way that cuts right to the heart of the matter , like his "screen door closer" description of varying the rate of clutch engagement .

Now along comes you , in a thread discussing power levels sustainable in a standard shift gearbox and were it not for the link to a "clutch tamer" product in your sig line I'd think that maybe your just here for the discussion also . But nope , there is that link trying to sell me something , something directly related to the subject at hand , and so of course with this serving of spam at the bottom of your every post your motive for being here seems abundantly obvious , you wanna sell me something . And as such , EVERY word from your keyboard is now suspect due to the suspicion that your "advice" could more properly be called "advertising" . Sorry , not looking to buy any clutch tamers today . Not very likely to tomorrow , either , and quite honestly , I resent you bringing the ugly suspicion of sales motivated tainted "advice" into this thread .

 

I've heard / seen too many GForce gears / T5's break...
I went with Astro A5... Thicker gears than stock & GForce...
Less cut angle to them, so less case flex... An upgraded GForce case (thicker) is about $300. You can upgrade the main shaft too & Astro rates them @ 600 tq... I did a lot of research and saw many reviews of people beating on them, running 10 second 1/4's and I think I only found about 2 bad reviews of all the good stuff... I'm happy with mine & Pro 5.0 shifter / McCleod clutch... Not much power over stock 91 TPI, but for future upgrades...

Rafael

 

If you look closer at my posts, you will notice that they are all guiding you in the direction of choosing a clutch matched to your T5's potential, as choosing a clutch with too much capacity is a proven quick path to T5 failure.

If I were trying to sell you a ClutchTamer I would be telling you that choosing a clutch with too much capacity is a great idea, as one of the ClutchTamer's basic purposes is converting simple destructive excess clutch capacity into much less violent reserve capacity.

 

SKUUUUUUUZZZZZZE me... shoulda typed 77 instead of 88...

Obviously I don't know what I'm talking about. I'm a total blithering idiot.

Sorry, gotta go to the hardware store and pick up acoupla screen door closers now.

Oh wait... I just remembered.... I don't HAVE TO, because I have a transmission that DOESN'T NEED THAT CRAP. It can actually handle V8 power NATIVELY.

I think instead of futzing around with a clutch and trying to make it the "fuse" in a manner of speaking, I'll just be content with changing to a transmission that CAN HANDLE THE POWER IN THE FIRST PLACE. Then I can buy ANY CLUTCH I WANT because I don't have to alternate-ethnic-engineer ANYTHING around the transmission to CRUTCH some weeeeeenie inadequate gas-mileage 4-cyl piece toward a better chance of avoiding self-destruction. "Survival" is NO LONGER an issue.

 

I do appreciate your explaining that your not trying to sell something here , but if so , why then the advertisement in the sig line ?

Like Sofa said , why should the clutch bear the brunt of the gearbox's inability to handle the power presented to it ? Rather than some "soft engagement" scheme wouldn't the prudent course of action to be to just go and get a gearbox that CAN handle the power level without loosing anything in the excessive slip of delayed clutch engagement ?

 

If a car is under 600hp it's going to be quicker with a 600hp capable T5 and the right clutch, than it will be with a T56 and the wrong clutch. Even with the right clutch the T56 is still going to be slower, it's just heavier and has more internal drag.

Your turn.

 

Who was it that once said, "it's better to be thought a fool than to open your mouth and remove all doubt"? Now I no longer have any doubt.

 

Sorry but you appear to have misread my motive for asking , this is not a "competition" , , , I'm asking you to validate your viewpoint that there is some benefit to delayed clutch engagement to save a "weak" gearbox VS getting a gearbox that will handle the anticipated power level coupled to a quicker engaging clutch ?

Yes , I do believe your "clutchtamer" IS tainting your view here , and hearing the method behind where you think this makes sense is what I was after .

Still , I can't believe a properly set up T56 could be all that much slower than a T5 whose clutch is deliberately holding back some of the available power so as to not grenade itself . Except for possibly marketing a soft engagement device , I just can't see the actual science behind your assertion . I'll take the T56's slightly less than optimal gearing to your T5's excessively slipping clutch any day and that was the REAL basis of what I wanted to get to the bottom of .

 

Is his logic really wrong here?

I've often considered taking my T56 out and putting a T5 in since my main competitive endeavor in my car is autocross... That's an easy, cheap 75 lbs to pull out of the car.

Granted, I have a T56, I totally buy the T5's are for four bangers argument. I already bought into it. But for a car that is ONLY used for autocross, I almost see the T5 as ideal... For road racing Im not sure... as I hear it's the 3 gear gears flexing apart that generally cause all the trouble.

 

A clutch is not an on-off switch, nor should it be. Every third gen with T5 had a sprung hub clutch and material that slips to an extent. Every clutch pack or band in your 700-R4, every TCC with or without PWM in a 4L60(E) has a designed application slow-down by design or sizing or you wouldn't be running an aluminum cased transmission.

Controlling with a damping device (or restricted hydraulic line) is just one way to provide for repeatable launch results. If you want ultimate consistency for bracket racing, great. Not something I want; if you're going to be a good driver, learn how to slip and apply the clutch.

Back on track,
I'd like to see longevity tests of a T5 with tapered mainshaft pilot bearing, and rear support bearing on the countershaft. And frankly, a material for the case section at the headset gearset bearings that won't slowly spread over 150,000mi. As far as I know, Astro uses the tapered mainshaft pilot bearing, the G-force case is normal aluminum die-casting, and the rear support bearing wouldn't be that bad to add, with lubrication being the main challenge.

Infernal, I've considered the same, inasmuch as I don't benefit from the T56 at the current time.

 

Sorry, the "your turn" was for Sofa, i should have included his quote. If Sofa were racing somewhere competitively, he would quickly find value in choosing the right clutch.

Here's the validation-

First, you must accept that there are two components to the energy your transmission's input shaft sees...
...The first is easy to understand, it's simply the torque that the engine is producing at that instant. If your engine's torque peak is 450ft/lbs @ 4500rpm, that's all the torque that the engine itself is capable of producing at any moment.
...The second component is inertia energy. Remember the crankshaft/flywheel/pressure plate are all connected, and effectively form a single flywheel. A flywheel is basically an energy storing device much like a battery, you must "charge" energy into it to increase it's speed, on the flipside you will recover a "discharge" of that stored energy as rotating speed is reduced. For the typical engine, this additional inertia energy can easily exceed 450ft/lbs, that's beyond the torque the engine is producing.

If an engine is producing maximum torque, it's operating at WOT.
...if that engine is maintaining a steady rpm WOT, it's net output is equal to it's maximum torque output.
...if that engine is losing rpm @ WOT, some inertia energy is being "discharged" from it's rotating assembly along side the torque it's producing, so the transmission's input shaft actually sees more torque than the engine is capable of producing.
...if that same engine is gaining WOT rpm, the transmission's input shaft is seeing less torque than the engine is producing, as a portion of the engine's energy is being "charged" into it's rotating assembly as it gains rpm.
This is the reason why varying a dyno's rate of acceleration can drastically effect the data it produces. If you were to increase an engine dyno's rate of acceleration to around 8500rpm/sec, the dyno would show almost no hp being produced, as nearly all of the engine's power production is being "charged" into it's rotating assy with little left over to do work.

A properly matched clutch does not hold back any of the engine's WOT power from the transmission's input shaft. What a properly matched clutch actually controls is the rate at which the rotating assembly loses rpm, and by doing that it is controlling the rate of inertia energy discharge from the rotating assembly. If a clutch with way too much clamp pressure locks up quickly, the engine loses rpm at a faster rate and the resulting inertia energy discharge acting on the transmission's input shaft is going to be much more intense. If clutch clamp pressure is reduced, it's going to take longer for that clutch to pull engine rpm down, and the inertia energy added to the engine's power will be spread over a longer period of time. Basically if you take a 450ft/lb discharge of inertia energy over .15 seconds, spreading that same energy discharge over twice the time period will cut that 450ft/lbs in half, effectively reducing that additional inertia energy torque spike from 450ft/lbs to 225ft/lbs. If we reduce clutch clamp pressure to the extreme, enough that it is no longer capable of holding the torque that the engine is producing, the engine is going to gain rpm while the clutch is slipping, and the clutch just goes up in smoke.

How is it possible that the heat of a slipping clutch is not engine power being wasted?..the heat/energy being absorbed by the slipping clutch is actually energy being released from the rotating assembly as it loses rpm. Remember, if the clutch is slipping but the engine is not gaining rpm, so every bit of the energy the engine is producing at that moment is acting on the transmission's input shaft. The engine's power is being met with an equal and opposite reaction at the input shaft, so there is no change in engine speed. If the engine were gaining rpm as the clutch is slipping then yes, some engine power is being released as heat/friction.

Another thing that's not so obvious, is that reducing the inertia energy torque spike makes it possible that you no longer have to overbuild the rest of the drivetrain as much to accommodate that spike. Now you can get away with lighter transmission, smaller u-joints, lighter driveshaft, smaller tires, you can now use more efficient radials and gain a few mph.

The ClutchTamer exploits the same physics as matching a clutch to the engine's power, but instead of relying on finding the right combination of lining and clamp pressure to properly manipulate a clutch's engagement speed, the ClutchTamer allows choosing a clutch with too much capacity and then forcing that clutch to slip for a few additional fractions of a second. Matching the clutch not only makes the car quicker, it also reduces the those destructive inertia induced torque spikes. I've got info to support that too, but i'm concerned that posting too much at one time will make this too hard to digest.

 

I should add that it's not typically the engine's torque that's responsible for stretching the cases and mis-aligning shafts, that comes when you add the additional torque from an inertia energy discharge. Remember that inertia discharge can easily add another 450ft/lbs, pretty easy to see how a 450ft/lb producing engine can put a total of 900ft/lbs to the input shaft for a fraction of a second.