6 speed LSD Mk1 gearbox build

[PW@Woodsport]

Thanks Tim, that's great, i'll get it added this weekend

[kaiowas]

Hi Paul,

I'm considering having a go at some of this over the winter. I'm having the kind of traction issues that will definitely be helped by a Torsen LSD and the lower gearing of the 6 speed conversion will be an added bonus.

Mine won't be as posh as yours, I'll probably avoid rebuilding the 6 speed which should keep costs and labour under control.

Can I just check whether it makes any difference whether you source the LSD from a 5spd or 6spd mk3 box and whether you use the 140 or 190hp Celica box (My initial research suggests they may have different ratios in them)?

[PW@Woodsport]

Hi, you can use the Lsd out of a 5 or 6 speed, doesn't matter. I would go for the 190 version for strength reasons, the gearing is pretty similar to be honest. You can use the mk3 6th gear pair to extend 6th even further if you like.

[gon]

Hi mate.
Make sure you get the 6 speed box from a Celica and not from a Corolla, the Corolla has the same ratios but the gear linkage is facing the wrong way.

In my view the ratios of the 190bhp engine (VVTLI) are better for performance reasons while the 140bhp engine (VVTI) might be better for fuel economy.

In my view the best of both worlds is to get a 6 speed mr2 mk3 gearbox and a Celica VVTLI gearbox.

This way you can get the LSD and 6th gear from the mr2 mk3 box and the rest from the Celica VVTLI.

The longer 6th gear from the mr2 mk3 box will give you fuel economy on the motorway, and the first 5 gears of the celica VVTLI together with the final drive from the VVTLI will give you a short ratio box with a long(er) 6th gear.

Celica VVTLI gear ratios
3.166
2.050
1.481
1.166
0.916
0.815
Final Drive is 4.529

Mr2 MK3 gear Ratios (5 speed box has same ratios but without the 6th speed)
3.166
1.904
1.310
0.969
0.815
0.725 (this one should give you a good motorway gear)

Final Drive is 3.941 (LSD)


I have made my conversion by using only a Celica VVTLI donor gearbox + the original mr2 mk1 box.

I have used all the ratios and final drive from the VVTLI.
I would prefer to have used a longer 6th gear but I could not justify the investment on another donor gearbox just for longer 6th gear as I did not want an LSD.

Out of interest if one does not want an LSD one can swap the planetary/spider gears from the celica open diff with the ones from the mr2 mk1 box and this way allowing the use of the original mr2 mk1 driveshafts.

If you use the mk3 LSD I believe original mr2 mk1 driveshafts will not fit.

Hope this helps

PS: I have to thank Paul for giving me this information in the first place and also for helping me with my conversion via email.

[kaiowas]

Cheers guys, this is for the sprint car so gearing wise my focus is on acceleration. With the standard mk1 box it's rare that I get above 4th in competition (usually need 5th towards the end of the runway at Woodbridge). If I can keep 6th long enough for it to be tolerable on a 70mph cruise (even that's all relative in a car with no sound deadening or heater) that'll be sufficient.

I've already sourced a 5 speed mk3 box for £100 which is a good start and I've got a spare worn out mk1b box to donate its bell housing, just a celica box and driveshafts to get now.

[gon]

you can cruise with the 0.815 6th and 4.529 Final Drive but 70MPH is about 3.5 or 4K RPM....

I have driven it to work like that for about 1 month (60 miles a day)

[Mk1Chris]

I cant 100% remember, but I think you need to make sure the mk3 box isnt from a jap import as they didnt all have lsd iirc.

[kaiowas]

Cheers Chris, I'm aware if that one and have been assured that the box I've found is from a uk car

[Jaspa]

I cant 100% remember, but I think you need to make sure the mk3 box isnt from a jap import as they didnt all have lsd iirc.

The jap mk3 gear box has different ratios too btw.

Roadster
1st 3.166
2nd 1.904
3rd 1.310
4th 0.969
5th 0.815
final drive 3.941 (with LSD)

MRS
1st & 2nd same
3rd 1.392
4th 1.031
5th same
final drive 4.312

(taken from http://www.mr2roc.org/misc/userpics/mar ... ratios.xls)

[bwrc]

Hi Paul,

I'm considering having a go at some of this over the winter. I'm having the kind of traction issues that will definitely be helped by a Torsen LSD and the lower gearing of the 6 speed conversion will be an added bonus.

Mine won't be as posh as yours, I'll probably avoid rebuilding the 6 speed which should keep costs and labour under control.

Can I just check whether it makes any difference whether you source the LSD from a 5spd or 6spd mk3 box and whether you use the 140 or 190hp Celica box (My initial research suggests they may have different ratios in them)?

I would suggest contacting aw11rally as he uses a 6 speed gearbox from a lotus exige in his rally car with a highly modified 1600cc engine. He has recently rebuilt the box with a custom final drive from Elite and had a thread with the details

http://www.imoc.co.uk/forums/viewtopic. ... &start=240

[PW@Woodsport]

Why? All of the info needed to do this is already in this thread?

[bwrc]

Because aw11rally has found that the standard 6 speed gear set is not ideal for a competition car used on twisty rally stages hence the custom final drive. Kaiowas wants to use a 6 speed box in a sprint car and as sprints take place on short twisty tracks he may encounter the the same problem.

There are a number of suppliers that offer custom gear sets and final drive options notably Jubba racing and Hanger 11 for the c64 gearbox because this is an issue that the lotus exige racing teams have had to overcome.

[PW@Woodsport]

Oh right, we do offer custom competition gear sets as an option in our Mk1 6 speed packages too, along with Quaife LSDs too, i've worked closely with Dave King at Quaife on this. Each transmission i build is tailor made to the customers requirements.

If anyone wants to know more about the Mk1 6 speed then just ask me, i'm the guy that invented it, we're currently the only Mr2 specialist worldwide to offer a Mk2 6 speed option too

[aw11rally]

Paul Woods is the man to ask.

We did our conversion before most, and in a rush with little knowledge and a lot of trial and error. Since then Mr Woods seems to have perfected the task of mating a C60/64 to the 4a-ge.

We couldn't have got ours working reliably without the valuable help and advice from Woodsport.

From experience the quaife diff works amazingly, very progressive and predictable, just what is needed in an MR2. Standard ratios are good for road use but far too long for competition.

We found the Elite final drive the most cost effective. Worked out at about £800 including fitting and a full rebuild / service (excluding bearings, synchros etc).

[stenky]

Guys, just make sure you get the C60/C64 gearbox if you want the 4.529 final drive. C63 appear to be quite common in UK celicas and that's the one I believe have (the one in Paul's photo-tutorial on page 1). Those are the less short/impressive transmissions.
I have counted 69 teeth on the diff crown gear and no way can you get 4.529 with 69 teeth on the diff, but you can get 4.312. So it appears not being the C60 nor C64. It could be C63 or C65 but those are according to the wisdom of interwebs mk3 only.

edit: nah, phucket. after re-reading the page 1, I am still confused about the final drives of the C series.....

[kaiowas]

More progress today, removed the LSD from my mk3 box and my Celica box has arrived.

[kaiowas]

First setback today. Managed to dig out my old mk1 boxes from the back of the garage, turns out they're both single hump. (I thought I had 1 of each type)

Now I've either got to remove the gearbox from the car (which I was planning to keep as a spare) before I can continue or source another box/bellhousing

[PW@Woodsport]

I can send you just a Mk1b bellhousing if you get stuck

[kaiowas]

Cheers Paul, that might be the best option otherwise I'll just procrastinate rather than getting on with what was supposed to be a nice garage based project. Don't suppose you've still got the driveshafts from that mk2 you were breaking have you as I still need some of those as well yet?

[PW@Woodsport]

Sorry i needed the shafts myself.

I can dig out a Mk1b BH for free for you though to help you along