Safe Horsepower Limit on stock 5 speed?

[Bugeye01WRX]

Hey guys

 

Sorry for all the posts recently.

 

I am getting ready to have my 2001 WRX tuned.

 

What is upper safe limit on the 5 speeds? I am keeping the stock TD04 and doing DP, Fuel Pump and STI TMIC, but decided to keep TD04 rather than put on a VF30 like I originally planned as I did not want to end up pushing too much power that would cause tranny to blow.

 

I have seen that I should get around 230 - 240whp with a stage 2 tune on a TD04? Does that sound about right?

 

And what sort of horsepower level would be considered the "safe limit," for the 5 speed tranny?

 

Cheers

[boon]

Yeah that's a realistic power level for a TD04.

 

Safe limit on the box will come down to how you drive it, but there are plenty of GC-era STIs running 5 speeds with around that 280whp mark without issues.

 

If you launch the car and drive it hard, you'll break boxes with factory power. It's not like they hit exactly 293.2hp and all the teeth fall off the gears.

[Bugeye01WRX]

13 minutes ago, boon said:

Yeah that's a realistic power level for a TD04.

 

Safe limit on the box will come down to how you drive it, but there are plenty of GC-era STIs running 5 speeds with around that 280whp mark without issues.

 

If you launch the car and drive it hard, you'll break boxes with factory power. It's not like they hit exactly 293.2hp and all the teeth fall off the gears.

 

So would it be better to put in say a VF30 or TD05-16g and STI pink injectors? That is the only extra thing I would need to add to get a good chunk more power? Or is sticking with the stock TD04 still gonna be great?

 

Ah I see yeah I don't launch car and I treat the box like it is glass so am trying to look after it.

[Loren]

My 5 speed took 3 years of brutal driving with over 400 whp before it broke... after fixing it... it only took 3 events to break again. It's just luck of the drawn sometimes.

 

 

[boon]

The TD05 is a 40 year old small truck turbo that should have been retired a long time ago.

 

A VF30 would go great, if you can find one and a set of pinks plus an STI intercooler you would get close to stock STI power levels.

[Timmah]

 

Go see my post.

 

Not sure why my photo isn't showing

 

 

No issues with my gearbox either.

[dmacnz]

I blow my first 5 speed with only around 200kw after 1 month 
next one blew in about 6 months. (Early ty752)

Got a later ty754 and ran 280kw and lasted till today! However they are a time bomb. 

[Loren]

I blew another yesterday, the third in 12 months... it only lasted 3 events. dogbox is on the way but not in time for the 7 events i have entered for the rest of the year, so will need to try another $500 piece of s***.

Edited October 4, 2020 by Loren

[Gripless]

What is failing in all these gearboxes?

Do you have short shifters fitted?

[dmacnz]

Breaking teeth normally due to the case flexing. 

[Loren]

18 hours ago, Gripless said:

What is failing in all these gearboxes?

Do you have short shifters fitted?

 

Teeth... 2nd gear twice... now third gear. No short shifter.

Edited October 5, 2020 by Loren

[Dairusire]

I'd definitely be putting a VF30 and STi Pink injectors in there. If you're not a savage they normally last quite long. 

 

Some are better than others but it's luck of the draw.

[Gripless]

So why not get the gears made in stronger material. It’s actually not that bad of a price last time I got some made. 

[Loren]

So why not get the gears made in stronger material. It’s actually not that bad of a price last time I got some made. 

As said above, I am waiting for a new gearset... I ordered it 2 months ago when the box before this one broke and was hoping this "temporary" box would last until it arrived. It's still a month away

Sent from my SM-G930F using Tapatalk

[Gripless]

I got that but not dog box ones. Just OEM style but better material. 
last gears I got cut the metal they used was the same as the 900hp hill climb cars and not straight cut. The cutting and time was the cost. 
 

 

[Loren]

51 minutes ago, Gripless said:

I got that but not dog box ones. Just OEM style but better material. 
last gears I got cut the metal they used was the same as the 900hp hill climb cars and not straight cut. The cutting and time was the cost. 
 

 

 

If i had known that that was an option I might have done that.

 

[dmacnz]

Look into blast plates. They attach to the side of the box to stop the case flexing. Normally the reason most 5 speed break. Even with good gear sets. 

[Loren]

4 hours ago, dmacnz said:

Look into blast plates. They attach to the side of the box to stop the case flexing. Normally the reason most 5 speed break. Even with good gear sets. 

 

I have seen them... look like snake oil. Straight cut gears don't cause the case to flex... so is the ultimate solution really. No big fat assed 6-speed is ever going in my car.

[dmacnz]

I’ve worked on a 5 speed dog box from a turbo eg33 large turbo car. Case flexing still screwed 2 straight gears. 
gearbox now was blast plates! 

[Loren]

If I'm still having trouble with teeth breaking after spending $$$ on a dogbox... I'll be putting a match to it and taking up golf.

[Dairusire]

48 minutes ago, Loren said:

If I'm still having trouble with teeth breaking after spending $$$ on a dogbox... I'll be putting a match to it and taking up golf.

 I mean, for the few hundred that blast plates cost, vs the cost/risk of breaking teeth of a dog gearset, I'd choose the blast plates. 

[Loren]

2 hours ago, Dairusire said:

 I mean, for the few hundred that blast plates cost, vs the cost/risk of breaking teeth of a dog gearset, I'd choose the blast plates. 

 

maybe, but think of how many things you could add to your car that *might* work. Blast plates weigh a tonne as well... so not something I would do on the off chance.

 

I've looked into a bit... just by doing internet searches... the guys that made them originally admit they didn't do any RnD... they were just desperate and tried something out that seemed to work at the time.

 

I will ask Al @ macbilt if he has any experience with them.

Edited October 7, 2020 by Loren

[Gripless]

Case flex was a Nissan GTiR problem. 
I thought you ate selector forks and bearing as well with flex. No amount of bracing fixed them. It slowed it but the flex would still kill them. 
 

Anyway I just took the offending gear and box to hear cutting services (Mt Wellington in Auckland) and they worked out the new gears. They remade so the same and some in new ratios as 5th was to tall. 
worked with stock synchros and all. There wa s the option of dog engagement but then that’s often cheap from older rally cars teams. 


 

[RedSVX95]

Hi All,

 

My stock auto on my 1995 SVX is having TCU and torque control/converter issues and looking at swapping out with a 5 or 6 speed manual. SVX is rated at 230hp so would a stock WRX 5 or 6 speed be ok? Any thoughts?

 

Cheers!

 

John 

[madmike]

On 11/10/2020 at 3:55 PM, RedSVX95 said:

Hi All,

 

My stock auto on my 1995 SVX is having TCU and torque control/converter issues and looking at swapping out with a 5 or 6 speed manual. SVX is rated at 230hp so would a stock WRX 5 or 6 speed be ok? Any thoughts?

 

Cheers!

 

John 

The torque would be the biggest killer for you.. 

It's really an unknown as to it lasting or not..