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Old 30-09-2019, 21:51   #1
Ett2 evo5
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What power can a stock 5gsr gear box take

Looking in to having a fast road engine built for my 5 just wondering what the stock gearboxes are good for thanks
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Old 01-10-2019, 00:53   #2
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Theoretically, over 1000whp.
Drag cars essentially utilize OEM spec gearboxes most often, although some utilize "faceplated" (having synchros shaved off to speed up shifts) gears, and dog-boxes including H and sequential.
In general truly impressive gearbox.
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Old 01-10-2019, 09:23   #3
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Isn't it the OE casing that is generally regarded as the weak point because it flexes under high torque loads?
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Old 01-10-2019, 12:13   #4
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Quote:
Originally Posted by Ett2 evo5 View Post
Looking in to having a fast road engine built for my 5 just wondering what the stock gearboxes are good for thanks
That's it, that's the only option for road use. You wouldn't put a 6 speed in A well re-built 5 speed is the best piece of mind, and also for the road-the GSR ratios are the best option.
What power output you looking for, certainly for road use wouldn't go over 450/500 max as its a pointless waste of expense.
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Old 01-10-2019, 17:28   #5
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That is a tricky one to answer as you do not know the health of the components that make up the gearbox, even if you have owned the car and treated it well from new (which I am guessing is not the case). I learnt quite a bit from Clive (Transmission Dynamics) whilst he built my drivetrain and there are many contributing factors that can weaken and/or damage parts, short and long term. That alone makes this an impossible question to answer with a decent degree of accuracy, without a full inspection (even then without X-raying/examining parts etc. you are still only able to make considered, but not gospel appraisals).

The question 'how much can a brand new gearbox with no manufacturing faults, built to close tolerances handle' would be easier to answer but you would still need to strip, inspect, examine and combine with many real world tests to get closer to the answer.

As an example, my car was running 605bhp and 560lbft and there were no noticeable issues with the gearbox whilst driving. The box was partially Ďbuiltí (not to a great standard it turned out - not built by Clive) with a few useful modifications/treatments. On paper, this was a great box; not the best, but far better/stronger than the original. Upon inspection, some of the parts were found to be incorrect and/or incorrectly positioned and many parts were out of tolerance due to wear. This then caused additional stresses to parts, which in turn continued to wear, but on an exponential scale (the wear exacerbated the wear).
The timing could not have been better as this could have reached total failure if use continued, importantly, likely not due to a single event, but a list of influences including time, power and type of use.

I decided to have my gearbox rebuilt (along with transfer box and rear diff), to the highest level that Clive offered, as I wanted to up my turbo size and increase power a fair bit. I was doing this for peace of mind and to build in safety margin (as the manufacturer did with the standard power original) not because my box was well worn (as I had no idea). I now have a box that, if serviced and used correctly, should more than handle the power that I plan to run.
Without going through the motions of strip, inspect, examine, replace parts for stronger and/or newer parts, treat, rebuild to custom/tight tolerances, I would not be able to say this with anywhere near as much confidence, in fact, iíd go as far as saying Iíd be shooting in the dark.

A pragmatic way of looking at at your question: Consider that the 5 speed was designed (and warrantied with car) to safely operate with a 300/300 (ish) car. There will of course have been a fairly large degree of tolerance built in to this (thus the warranty). Whilst the warranty doesn't last as long as the life of the car, the gearbox has been designed to last for the life of the car, so maybe 150 to 200k miles min? SoÖ. Could you put 700lbft through an good/healthy box once, with gentle application of power and the box not break? Maybe; some reports would suggest that this is possible. Could you run 700lbft for 50k miles with several track days and launches mixed in, without failure? Almost certainly not. So there are several factors that must be considered.

To answer your question directly, you will need to make your own mind up, considering the following:
- The lower the power, the less stress on key components.
- Previous service intervals and oil used.
- Milage of gear box (original to vehicle?).
- Use that car has had throughout itís life (track, abuse etc.?)
- What do you plan to do with the car?

All of the above will help you to make an informed decision, but unfortunately will not get you to your answer.
If you can get it inspected, that is going to give you a much better idea. Clive W would be able to strip, inspect and advise better than anyone on this forum.



On a side note, and to add a little balance to the 'what is too much power for the road?' debate, I had 600/560 and wanted more. Mine is a pure road car, no crazy cams, no silly power bands or peaky turbos, just a faster version of the original car. Did I need more power? Certainly not! The thing was wild!!! Did I want more power? Absolutely, yes! Why? because I wanted to accelerate faster.

Believe me (living in the sticks with lots of small lanes), you can put 600bhp down everywhere. Granted, [the following is a practical way to work out 'what is too much?'] *the duration of time that you have your foot to the floor is shorter (to achieve a given speed), but the frequency of foot to the floor remains the same (per driver).* Your top speed does not have to increase with power, but your acceleration can, if you want to press the pedal to the floor (remember, you do not have to if you dont want to or the environment/conditions do not allow).
If you like being pushed into your seat by the acceleration of your car, more power and/or less weight is the only answer Iím afraid!

Hope this essay helped in some way
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Old 02-10-2019, 17:22   #6
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Cupid Stunt,
Nice of you to try to contribute and help the member.
Quiet honestly, if you can accept constructive criticism: its huge story with no conclusion.

Fact is simple, there are tons of drag Evos running 8s and 9s, and track Evos winning TAs, using OEM gearbox essentially.
We are speaking of 5 speed, its not an Evo 8/9 MR here in question.

We could philosophically examine each and every component and hypothetically bring 100+ experiences and so forth. No need.

OEM is great, and once in a while it needs a fresh-en up, to stock is good enough until next time in 100K miles.

CliveW is genius and he can and will make it that much better, but most of the fellas in the world abusing Evo 5 speeds have not met Clive and are doing fine.
I met Clive, and I am grateful for it.
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Old 07-10-2019, 22:53   #7
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Old 07-10-2019, 22:58   #8
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Quote:
Originally Posted by Blood Speed View Post
That's it, that's the only option for road use. You wouldn't put a 6 speed in A well re-built 5 speed is the best piece of mind, and also for the road-the GSR ratios are the best option.
What power output you looking for, certainly for road use wouldn't go over 450/500 max as its a pointless waste of expense.
6 speed is an option now that I have spent a huge amount of time developing it, with the fitment of Albins billet gears, in conjunction with lots of tweaks and modifications to iron out all the inherent design faults.

I have customers running from 650bhp full weight road cars to a 750bhp Time Attack car with my 'built' 6 speed.
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Old 15-11-2019, 17:08   #9
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Quote:
Originally Posted by Clivew View Post
6 speed is an option now that I have spent a huge amount of time developing it, with the fitment of Albins billet gears, in conjunction with lots of tweaks and modifications to iron out all the inherent design faults.

I have customers running from 650bhp full weight road cars to a 750bhp Time Attack car with my 'built' 6 speed.
Only just remembered this thread

Should have car back from Mark soon, will keep you posted!

Great news that you have now got involved with the 6 speed, sounds as though you've sussed it... Great results!
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