FAO: people running big power 1*2s, JC5 gearbox strength?

[jack_davey]

Hi all, I'm soon going to converting my 182 to a 2.0 turbo, using an F4Rt from the megane/laguna coupe. I'm a bit concerned about the gearbox being up to the job.

Has anyone else running turbo conversions or throtttle bodies etc had any problems?

I suppose the clio cup race cars take a fair amount of abuse and they were putting out something like 200bhp at the flywheel as far as i know.

My gearbox feels great as it is, very smooth and quiet, I was thinking of replacing the bearings and oil seals maybe just as a precaution.

Any thoughts?

 

[Ali]

meg engine....Good luck!

 

[Fred@BTM]

you do know the JC5 doesn't bolt upto the F4RT block?

 

[jack_davey]

yeah I do, I'm modifying the block to suit.
I'm just about to complete a degree in engineering and done a fair bit of machining etc, if it doesnt work it hasnt cost me a lot to find out.

I'm not sure if the JC5 will handle the power though, I dont intend going mental with it, the F4RT should provide enough power in standard trim.

 

[Ali]

There's some JC5's running over 250-300brake so providing you don't bang it through the gears or launch it, it'll be fine.

 

[jack_davey]

Yeah that's what I thought, I suppose there's a fair amount of people running throttle bodies etc giving them a fair amount of welly and they seem ok.

I had considered using a 197 gearbox, but I dont know if that fits in the mk2 and pairs with the driveshafts etc, and I think it uses a hydraulic clutch?

 

[Fred@BTM]

the megane box does fit you know?

 

[jack_davey]

really? why dont more people do this conversion?

To what extent does it fit? Would I need to fabricate mounts? Do the driveshafts fit ok?

Just realised my comment about the clio cup race cars is totally irrelevant as they use the sadev 6 speed sequential box

 

[Fred@BTM]

you will have to fabricate box mounts and use custom driveshafts, plus convert to hydraulic clutch

but it does fit in the bay! JUST

 

[Fred@BTM]

 

[jack_davey]

yeah there's the issue, custom driveshafts etc and converting the clutch operating mechanism might be a tad on the expensive side!

Isnt the gear linkage completely different too?

I dont plan to spend massive money, this was intended to be a cheap conversion. Seeing as 182s have plummeted in value, I opted for this rather than buying something quicker, plus its always nice to have something original!

 

[KungFuSpaghetti]

box will be fine, I have 250bhp running through mine and it's absolutely fine, then again I dont change gear quickly which seems to be the route cause of so many failures.

 

[Fred@BTM]

well you'd just use the gear linkage off a megane RS

hydraulic clutch won't be that bad (V6 pedal box bolts straight in)

driveshafts and box mounting will be the ball ache, i gave up in the end

 

[fad]

This sounds good

 

[Icarus]

box will be fine, I have 250bhp running through mine and it's absolutely fine, then again I dont change gear quickly which seems to be the route cause of so many failures.

Power means nothing as far as the gearbox, clutch, driveshafts etc. are concerned. Torque is what actualy limits (breaks) them. You could quite happily put 1000bhp through a JC5 as long as it was accompanied by less than 200ftlbs or so (although realisticaly input shaft RPM would come into play at that point).

To the OP - limit the torque to circa 200ftlbs and it should be fairly okay.

Cheers
M

 

[KungFuSpaghetti]

Power means nothing as far as the gearbox, clutch, driveshafts etc. are concerned. Torque is what actualy limits (breaks) them. You could quite happily put 1000bhp through a JC5 as long as it was accompanied by less than 200ftlbs or so (although realisticaly input shaft RPM would come into play at that point).

To the OP - limit the torque to circa 200ftlbs and it should be fairly okay.

Cheers
M

Well yes this is true, you can go further by saying it's not just the headline torque figure either, but how and where it's delivered and over how wide a rev range. Either way, these boxes are garbage, I've had enough failures for varying reasons to come to that conclusion and had to change the way I drive accordingly. Certainly never had this kind of trouble with Ford boxes, which is saying something! lol

 

[jack_davey]

yeah sure I appreciate its the torque that actually breaks it.

Thanks to Icarus and Fred for your help so far, are the megane drive shafts just too long? Could you not get them machined down and resplined?

 

[Icarus]

Well yes this is true, you can go further by saying it's not just the headline torque figure either, but how and where it's delivered and over how wide a rev range. Either way, these boxes are garbage, I've had enough failures for varying reasons to come to that conclusion and had to change the way I drive accordingly. Certainly never had this kind of trouble with Ford boxes, which is saying something! lol

It pretty much is the headline figure...... hence why 99% of gearbox manufacturers specify a max constant torque figure and for the most part no one specifies a transient figure. Okay you can get into situations with open diffs and wheel spin that can cause much higher loadings but for the most part any torque output under the constant loading figure will result in a reliable box.

Nothing wrong with the JC5 box to be honest, it's a boggo road box. Treat it like a gearbox in a race car though and it's only going to go one way... as will any synchro box.

How come you've changed your username BTW

Cheers
M

 

[Icarus]

yeah sure I appreciate its the torque that actually breaks it.

Thanks to Icarus and Fred for your help so far, are the megane drive shafts just too long? Could you not get them machined down and resplined?

Yes there are a few places that'll do it now, including Reproprop. It's a fairly simple job to be honest.

No reason you can't reduce the torque output of a 225 spec lump without reducing power though.

Cheers
M

 

[jack_davey]

Anyone know what the maximum constant torque that the JC5 can take is?

What are peoples thoughts so far then? Fit the JC5 or use the six speed (unsure what its called) from the megane?

 

[Icarus]

177 ftlbs sticks in my head for some reason, I'll have a look and see what I can find.

I'd be tempted to drill the block and use a JC5 for packaging and weight reasons with a suitable cal in the engine control to ensure good power but a reasonable level of torque.

Cheers
M

 

[KungFuSpaghetti]

It pretty much is the headline figure...... hence why 99% of gearbox manufacturers specify a max constant torque figure and for the most part no one specifies a transient figure. Okay you can get into situations with open diffs and wheel spin that can cause much higher loadings but for the most part any torque output under the constant loading figure will result in a reliable box.

Nothing wrong with the JC5 box to be honest, it's a boggo road box. Treat it like a gearbox in a race car though and it's only going to go one way... as will any synchro box.

How come you've changed your username BTW

Cheers
M

I've killed 5 JC's over the years in vairous situations so am just going by my real world experience of JC5's, which so far hasn't been good. Ironically all of them were killed with less power than I have now, with this current one lasting the longest. Like you say, treat it like a race car and it will die, but that applies to standard power just as much, again, never had a problem with Fords. I dont really concern myself with the theory side of it all, only how it's affected me in reality, that is my unfortunate experience of JC5's thus far.

 

[jack_davey]

177ftlbs? F*ck if it is that low, I might say forget it! Because the whole reason I wanted to do it was to get some better low down torque!

 

[jack_davey]

Fred, you seem to know what you're talking about and you've had a crack at this before...

Do you think it's possible?

Did you manage to get the ECU to work with the clios instrument panel etc?

Thanks,
Jack

 

[Fred@BTM]

na, all i did was trial fit the F4RT and megane box in the bay to see if it would go

anything can be done, i reckon the way to go would be Mitsubishi evo engine

 

[Icarus]

177ftlbs? F*ck if it is that low, I might say forget it! Because the whole reason I wanted to do it was to get some better low down torque!

Well theres no reason why you couldn't have 177ftlbs from 2000RPM to the rev limiter. Assuming thats at 7K it'd give you a peak power output of around 230bhp i.e. standard R26 power.

Cheers
M

 

[Brett]

There are a fair few 1*2 Turbo's running JC5's. Ryan K runs one but if you look in his thread he was looking at other options too. You could go down the route of if it breaks i'll just fit another box if you are able to fit it yourself etc.

 

[Gaz_]

172/182 Turbo = Money pit.

End of thread tbh

 

[Icarus]

172/182 Turbo = Money pit.

End of thread tbh

Not if its built and calibrated properly!!

Cheers
M

 

[jack_davey]

Well I've got the engine already, i can see it being a money pit spending circa £6k on k-tec's conversion. I've just gotta get it running and driving the wheels.

I'm thinking use the JC5 and perhaps use uprated bearings etc! I just need the help of Icarus by the sounds of it! lol

 

[Icarus]

I think you'd be okay with a standard good condition box to be honest. If anything you're likely to have a diff failure if you really batter it with sticky tyres on/ Obviously the wear rates will be much higher with the greater torque loading but I'd still expect 25K or so from a fresh box before it needed rebuilding if used relatively hard.

You can shot peen, cryo treat, DLC, web, weld and polish bits of box to your hearts content but unless you need it to be 100% bomb proof for a known distance (i.e. in a race car) then for the most part it's easier and much cheaper to accept you'll get decent distance from it but it'll break at some point. They aren't hard to change on the Clio either ;-)

I'd pay attention to box lubrication though, specificaly oil temps. Get a thermocouple of there to give you an idea of box/oil temp and fit a gearbox oil cooler if required. Chances are it'll live a lot, lot longer that way!

Cheers
M

 

[Mark One]

although what Icarus is saying is bang on the money as it always is.....
Have a little rethink.
If you really want to run 250lbft, then go ahead and run it through a JC5 and keep a spare in the garage. If your the kind of person that wants to fit a megane F4R, then you shouldnt have trouble doing a gearbox in a day.
Plus tbqfh, drive it nicely and it'll hold plenty more than ~177lbft for a good while.
Rules are no fun, and engineering is done with factors of saftey. Try it and see.

My personal take on it is: If you need it to be cheap, run a JC5. If you've got a little more to spend, run a meggy 6spd (the mount looks pretty straight forward and the shafts can be done by shortening 225 shafts). If you've got a little more go for a VAG 20vT and box, or an EVO engine and box.

edit: pretty much what icarus has gone and said above lol!

 

[ashy_gtt]

mine runs 240bhp and 230lb/ft and i've had no problems to date. Guess it depends how you drive aswell but I don't think you can say the limit is 177lb/ft when it clearly isn't.

We've fitted a 225 engine into a R5gtt with a JB3 box and again had no trouble (touch wood).



Although if the F4Rt lump can be fitted with the 6 speed box I would go that route.

 

[Mark One]

someone please correct me if im wrong but 400-£500 rings a bell for shafts made up from OEM parts.

 

[Icarus]

mine runs 240bhp and 230lb/ft and i've had no problems to date. Guess it depends how you drive aswell but I don't think you can say the limit is 177lb/ft when it clearly isn't.

We've fitted a 225 engine into a R5gtt with a JB3 box and again had no trouble (touch wood).



Although if the F4Rt lump can be fitted with the 6 speed box I would go that route.

How long have you put 230ftlbs through the box for though? And I mean in terms of constant loading. I'm guessing you've not done 12 hours at constant point of peak torque.

A constant load limit is just that. Usualy on none cooled FWD transaxles the failure mode is gearbox oil temperature related, once at a certain temperature the lubricating properties of the oil degrades, which causes more friction, which causes more heat, which degrades the oil further until the box fails.

Worth noting as well that the 230ftlbs is a transient figure i.e. you achieve it and as the revs climb this figure drops off. How much torque are you making at the point of peak power?

The ND0 box is fairly weighty so I'd want to use the JC5 if at all possible, 6th is very long on the Meg ratios and wouldn't be much use in a Clio.

Cheers
M

 

[jack_davey]

Ashy, if you dont mind me asking mate how long have you been running it?

Icarus, why is it the diffs go first? is it the shear force of trying to turn both wheels against their will (if they are very grippy tyres)?

I'd really like it to be as reliable as possible really, so if its a case of spending a couple hundred quid to make the gearbox a bit stronger, I'd prefer that to breaking down to only spend the money on a replacement gearbox!

 

[ashy_gtt]

Its been running on that box for about 2 years give or take. In that time I've done a few track days and a handfull of runs up the strip. In terms of miles I've no idea tbh. But as its a weekend toy everytime I take it out it gets a hard time :evil:

The proof of the puddings in the eating

 

[Icarus]

Diff failure tends to be when you unload and reload the diff rapidly i.e. during wheelspin. If you manage to spin up a very grippy tyre then the load through the box when it grips again is what causes the damage.

The usual failure mode of JC5's is crunchy gear selection. I tend to think that for the most part this has something to do with the fairly weak selector forks and the typical owner of a 172/182 wanting to get the next cog in ASAP on several occasions. Theres been the odd JC5 have some internal components make a bid for freedom through the casing but then again this too could be due to a shift fork failure as if you do manage to engage two gears at once it usualy results in fairly epic and amusing explosive box failure ;-)

Cheers
M

 

[jack_davey]

well the car is going to be used on the road, with the occasional track day.
However I'm not the sort of person to spin the wheels up at every given opportunity, and I'm very gentle when changing gear.

Any upgrades you can suggest? or maybe just frequent transmission oil changes?

 

[Alex_X93]

The diff in my old r5 punched hole through the box casing not funny.