6 Speed Gearbox

[Alan_M]

There is a lot of love going on for my 306HDi, but one thing I hate is the buzz at motorway speeds. A lot of my miles is commuting a junction up the M4, and at a reasonable 70mph, it is far too buzzy for my liking. A 6 speed box would be a great addition to the car.

Having a read about different threads, there are a couple options. The GTi6 box has a reputation, and is far too short for a diseasal. The other is the newer ML/ME boxes. A chap over on Drivers has built a 306 S16 using one of these boxes, ME I think and an ML bellhousing (from an ML boxed XU - 406 2ltr turbo I believe).

Now, I understand there is a fair amount of work like shafts, hydraulic clutch and cable shift but these don't faze me one little bit if I get a taller final gear. But, I'm curious as to how much the subframe has to be chopped for the bigger ML/ME diff.

Anyone have any info?

[bashbarnard]

Its a lot of hassle. Everyone likes the hdi box cause the xud one revs high as hell!! Id recommend soundproofing the car a bit.more really easy to do lower cost. Leas mods. And there is a thread on here already about with people having great success. In fact im doing mine soon

[Poodle]

Do it, please! And write a guide as you go, for all the mugs that feel like taking a punt themselves.

[Paul_13]

What revs you doing at 70mph?

[zx_volcane]

Do it, please! And write a guide as you go, for all the mugs that feel like taking a punt themselves.

It's going to be a ballache to sort out, but I for one would love a modern 6 speed hdi box on my car.

[toseland]

i dont think its so much fitting hte box to the engine.. that is simply a case of a plate and adaptor bearings..


the real issue will come specifically when you try to connect the gear lever up, also with the driveshafts..

[Ruan]

the real issue will come specifically when you try to connect the gear lever up, also with the driveshafts..

Box will fit to engine no problem at all - it's essentially the same block used.

Gear lever is easy enough as it's cable shift, shove it where you like...

Driveshafts are an issue, but cups are easy to find, just gotta get them the right length - which AFAIK is a custom job.

Clutch will have to be hydraulic, but there are methods of doing this.

Fitting box into engine bay is a big problem, the diff is vastly bigger, mounts don't line up etc....

[toseland]

i was assuming a diffrernt brand box, other than pug

[Poodle]

It's going to be a ballache to sort out, but I for one would love a modern 6 speed hdi box on my car.

Yeah, snap, the 306 does feel like it's missing a gear at the top end. Think of the mpgzzz!!

[Eeyore]

id love to see this if anyone can do it!

[Toms306]

Agreed, always wanted an extra gear in the HDi!

[powerandtorque]

Another possible option is the Xsara HDi 110 gearbox which, I believe, has longer ratios. Possibly the rare 206 HDi Eco too?

What exhausts are people running if they're finding a HDi "buzzy" at motorway speeds though? It's only doing ~2400rpm at that speed so it's hardly short geared, and I've always found them a quiet cruiser with a standard exhaust fitted.

[Eeyore]

I have also found the hdi quiet at speed. Never been a problem for me!

[welshpug]

that's a good shout Anthony, appears they run a 3.55 FD instead of a 3.68, they both run the particularly long 0.65 fifth.


one problem with the ML6C is that it comes from vehicles running larger wheels, therefore wont have very long final drives or 6th gears, C4 for example used a 3.94 final drive, though 6th is a 0.53.

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LOL

correction, my gear calculator says 7k rpm on a C4 box in top on 195 55 15 is 225 mph

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70 mph cruising would go from 2401 rpm to 2316 on the 110 hdi BE4 box, and 2175 on the ML6C.

one thing to consider however, is the efficiency of the HDI engine, no point dropping it to 2175 if its not making boost as it'll never hold the speed.

[Ruan]

To be fair, my v50 with the Ford MMT6 box is doing just under 2k at 70mph - i'd guess at around 1930rpm... Depending on turbo and torque delivery, you could easily make an 8v HDi cruise there.

6th is 0.564 with a 3.234 final drive on the 5,6,R layshaft.

[zx_volcane]

Problem with the hdi box as it is, is the ratios.

5th is fine for cruising, but getting there is not pleasant.

Ideally want something like the gti-6 box, 5 lovely equal ratios, then a long 6th for cruising.

[welshpug]

not that IS long Ruan!

and if I'm right with the tyre size (205 55 16 or equivalent) then 70 mph is 1725 rpm :o


gti6 box does not have a "long cruising gear" gaps between the gears are fairly equal, 6th is less than 200 rpm lower than my Xsara gearbox.

[Toms306]

Personally I don't like the HDi 'box at all! 1st is far too short and pointless. 5th isn't long enough and is noisy at speed. Only decent gear ratio is 3rd lol! Well, it is until the synchro starts to fail.

I'd be interested to see a 6spd on a HDi tbh, it's been talked about several times but no-one ever attempts it!

[powerandtorque]

To be fair, my v50 with the Ford MMT6 box is doing just under 2k at 70mph - i'd guess at around 1930rpm... Depending on turbo and torque delivery, you could easily make an 8v HDi cruise there.

It would cruise at 70mph fine, but throw in a bit of traffic bunching that you get on a busy motorway (or worse, get caught behind some trucks elephant racing) and an 8v HDi will drop off boost with that gearing - roughly 1600rpm at 60mph

Guess then you've the question of whether the noise and possible economy benefits of a taller top gear would be worth needing to drop down more often on congested motorway traffic. Wouldn't bother some people, but that would very quickly bug me on my daily commute where traffic is constantly fluctuating between 50 and 70+ mph.

[Toms306]

While you're fitting a 6spd 'box it'd be rude not to fit a VNT at the same time.

VNT and a long 6th would make for epic MPG.

[zx_volcane]

gti6 box does not have a "long cruising gear" gaps between the gears are fairly equal, 6th is less than 200 rpm lower than my Xsara gearbox.

yah exactly, so something like the gti-6 box up to 5th gear + a long cruising 6th gear would be ideal

70mph with the xud + the gti-6 box was silly rpms on the motorway and mpg was adversely affected

[Piggy]

Is there no way to change the final drive on a GTi box?

[toseland]

Is there no way to change the final drive on a GTi box?

you should always be able to change the gears./


it just depends how much you are willing to spend..


i could have a 5:1 reduction in the final drive of the low ratio on the transfer box on the vitara, but its nearly £400 for the gearset alone.

[Ruan]

The problem is that the internal gearing in the GTi6 is quite short, therefore the final drive is already LONGER than that of a HDi, so without insane customisation of the diff housings and custom CWP, you're barking up the wrong tree...

The GTi6 box is useless for conversion, it's not that strong, I had one in my car and turned the gearbox oil silver unicorn blood in roughly 2 months.

In regards to the MMT6, I don't think it's THAT long, 1720rpm I doubt is correct at 70mph... Unless my speedo is very out! I'd say it's between 18-1900rpm at 70mph - I'd suspect that's figures pulled from something else that's Ford/PSA. And especially in regards to power, yeah sure, up long hills I have to change down, it is a very torquey engine (252lb.ft at 2000rpm) - but the MMT6 is just a perfect transmission in terms of ratios, lovely short 1st, 2nd, 3rd, but gets longer into 4th and 5th and a very long 6th... Whether you could fit one to a 306 I doubt, the diff is absolutely gigantic as it has a different diff on each layshaft as I understand.

I've never driven a ML6 so couldn't comment on what the ratios are like, but if I had the option of fitting one, I'd be trying for an MMT6. No driveshafts will fit mind, completely custom job!

[welshpug]

whats this talk of layshafts? isnt that a rwd thing?

I dont know ford boxes mind, all I know are be, ma, sadev fwd

all they have is input and output shafts.

[Ruan]

I'll be honest, I'm no transmission expert, I'm just going off how I see it in my head...

The MMT6 appears to have two final drives, depending on what ratio is selected so gears 1-4 have an fd of 4.566 and 5,6,R have 3.234... Same idea as a Double clutch design as I understand it... These gearboxes use two 'layshafts' with different FDs...

[Ruan]

I don't think any PSA boxes are like that...

[Piggy]

Ruddy heck thats a simple yet complex idea all at the same time.

All that work to fit one to a 306....may aswell just fit a DGT box!!!

[darrenjlobb]

Gearboxs are a real PITA, in some ways we have it great, but others not so..

The boxs themselves are all super strong (well apart from gti6 / tu boxs), as in, ive never had issues shredding the diesel boxs from power, like the tdi boys do constantly,and they are great to rag / abuse with great synchro / ragging ability.

The let down is just the annoying as frig offset gear ratios, theres always annoying steps that just ruin the drive IMO, which is very frustrating when you have build a chronic motor / its let down by the box. The only box that avoids this, is the gti6 box, which imo, is an epic drive, and has fantastic ratios, and with a slightly longer drive would be perfect for the ultimate rag car. However these boxs are fairly weak, and tend to give up alot, and although I never broke one, based on Toms exerpiance, I think if i had done any serious ammount of miles I likely would have..that said id still be in two minds weather to try it again and see for myself...

I bought an ML for my DT, but it never got fitted in the end, still sat there, also a pair of matching shafts for the joints, and slave / master cylinders for the clutch. But I think id like to drive one of these cars before i even thought about going to the effort of fitting one, as I never have, and frankly have no idea if the ratios are acaully any better? Or at least equal?

[silverzx]

If it makes you feel any better my punto does:

100mph 3000rpm
90mph 2700rpm
80mph 2400rpm
70mph 2250rpm
60mph 1800rpm