ajamesc

Anyone know what one to use for as near to a 3.6? Or anyone using the 3.9 ratio type and if so how has it affected your top end?
Also any pics as some of the ones on eBay have some odd looking mounts.
I'm going to remove my 7.5 gripper diff and fit one

Caddyshack

I am in hampshire and have a 3.9 which was rebuilt by bara and set up for the Cossie, I have the mk fitting kit which you will need.

I haven't tried mine yet as the gearbox gave up, my car is up on Ramps now ready or the diff to go on as soon as my tranny jack and new billet diff hanger turn up.

Mark at mk can supply the kit and tell you which diff you need. I think the gearbox drop gears may need to be changed for the 3.9 diff but best check with bara on that, he is the man to rebuild and I wonder if he has an alternative or same fitting kit.


You can come and see my diff and kit if you want?

ajamesc

Mines a rear wheeler. Was more thinking of just getting a used one from a beaker then rebuilding it my self. I'm going to get my beam modded to 6 degree by him so I'll send it off to be modded so not sure if I'll need the hole fitting kit?

smiley

Alright pal im sure the 3.9 is more suited to the 4x4 and the 3.7 the rwd
Im also having one bara sourced mine give him a call he.ll answer all your q.s he advised me to have drop gears and an uprated vcd. Good for 600 bhp i hear and hope lol going for oppliger bigtooth but std ratio from bara

Caddyshack

I am sure you will need a fitting kit for the diff as they are VERY different to the Cossie, 3.7 is the way to go on 2wd. I THINK the 2wd needs a few mm machined off the mk adapter...ask mk. If you are fitting it then bear in mind you may need a little "fabrication" to make it fit, a little nip here and tuck there....they don't come with any instructions.

Bara set up the ramp angles etc to make the diff work for me, It is all well beyond my limited skills.

ajamesc

Im hoping to send my beam off to him have it modded to 6 degree and made ready for a supra diff then set back with what ever fitting bits I may need for the prop and drive shafts. I'll may give bora a ring to find out what serial number diff I need but not sure if there give info like that out if I'm buying off them

Caddyshack

I may be talking bollox but am sure the beam will still nead the kit too. If you are buying from mk then let them give the advice but it was bara that mentioned the drop gears to me. I got my diff from mk and bara rebuilt it, tested it, painted it and set it up.

ajamesc

Yeah I'll give mk a call when my beam is out. Mean while I'll look out for a diff stripping painting and re building it is some thing I'll do my self at work

smiley

Caddys bang on you do need the kit im having a 6 degree off mark and asked him if it was suitable with the supra diff kit and is also mk diff mount

LHD220Turbo

iTrader: (4)

cant andy robinson fabricate your beam & fit up the diff for you?

ajamesc

i have asked him about this in the past and he said he has the soft wear to design something but that would work out expensive. I've no idea how a 6 degree beam needs to be done to tell him how or in what way to mount things for it to work as it needs too. Plus he would need too make up a kit to mount the diff and mate it too my prop and drive shafts. Most likely be cheaper and simpler to get mk to do it. Also it needs to be done before the engine is running as my new exhaust system will be made round the new diff and modded beam so really need bits I can just buy

LHD220Turbo

iTrader: (4)

thats a shame; there is a thread on here somewhere about the exact modifications you have to do

but to be fair MK do a brilliant job from what i've seen

ajamesc

yeah his work looks spot on! I'll also fit adjusterball lower arms on the front then when it's all running I'll get Andy to corner weight it and set up the suspension

Sonic Boom

iTrader: (11)

I've got one of MK's rear beam it's spot on the fabrication is excellent I also have his Supra diff conversion too.

I'm running a 3.9 CWP (Rebuilt by Bara with a Weir Stage 1 kit in) in mine it's so much better I topped it out at 165 mph at Bruntingthorpe earlier in the year can't see why you'd need to go faster than that anyway unless you're doing top speed runs.

Over the winter I'm changing to a 4.3 CWP it'll suit Hilllcimbing even more I am running 255/40/17 888's on the rear thou.

By the way there are no ramp angles to set in a Supra Diff you can only adjust pre load mines set at 100 ft/lb break way which I find ideal.

You can off course fit a Gripper unit to the internals of the Supra but they aren't cheap.

Rich

smiley

Good info rich have you uprated box? What power are you running mate?

Caddyshack

Sorry, I meant pre-load...I think?

Do you run std ratios in the box? I thought you were close ratio too?

Sonic Boom

iTrader: (11)

I still run a T5 with a John Reed close ratio gearset all super finished and fitted by Bara.

Oh and I'm running 631 bhp

Rich

smiley

Sweet

ajamesc

How much are people paying to have these diffs done at bara with the vc setting adjusted?
I picked up a 3.7 one for 150 just need a fitting kit and 6 degree beam now but that will come once my new engine is in. But needs doing before I have my exhaust system made

Sonic Boom

iTrader: (11)

It's Ł400 mate as long as you don't need bearings.

Rich

scoooby slayer

iTrader: (4)

I cant help at all tbh but I do know the diff in my old mk4 supra was only the small case one and I threw loads of power at that (800 hp) with r888s and it lapped it up, the complete opposite to a cossie 7.5" planet gears gone poop turd lol


ive got 4 old cossie diffs somewhere, I did 4 launches in my last saph and blew 4 diffs lmfao
planet gears everytime

ajamesc

After pulling the back cover off my supra diff I can't see why the c.w.p is so much stronger lol it don't look much bigger! But it works I'm not too sure what to do now a straight re build I can do myself and the bearings and seal are only about 70 quid! But I've no idea how to up rate it's locking rate and I'm not sure how well it works in standard form

turbotrev

Out of interest why are you removing your gripper diff to replace with a supra one mate?
I thought the grippers were meant to be pretty good??

Cheer Paul

ajamesc

The gripper diff is a very good and strong diff but the c.w.p is not. It's got a hewland engineering one in it at the moment but I'm always worried I'll brake it. I broke the standard one flooring it coming off a roundabout already on the move in 2nd. The supra one is so much stronger and my new engine should have a lot more power and torque from low down. Also I'm changing my beam so thought I may as well as I can still get good money for the gripper

ajamesc

Well ordered a fitting kit from mk today as he had 1 on the shelf so should get that next week. 450 for a re build from bara with the up rated spring from weir

Sonic Boom

iTrader: (11)

Can't go wrong with the Supra Diff with Weir kit in mate I've given it absolute death and it keeps on going.

Rich

turbotrev

Ahh gotcha mate, yeah you've proper destroyed that cwp eh!!!
What what was you running when it stripped that out of interest?

Cheers Paul

ajamesc

an m.a.d 500bhp set up on a gt30

BRAMMER

iTrader: (23)

Just double check what you have is what you actually bought as i thought i bought a 3.7 but in fact turned out to be a 3.9 which suits me but some it may not.

3.25 = 39/12 = MA70 Group A (Special race class)
3.727 = 41/11 = MA70 3.0 GT turbo
3.909 = 43/11 = GA70 M/T, most MA70
4.100 = 41/10 = JZA70 M/T and some A/T, some N/A MA70
4.300 = 43/10 = GA70 A/T, also some MA70
4.556 = 41/09 = GA70 GT

ajamesc

It has 41 crown wheel teeth that means it's a 3.7 so I'm told and its a limited slip

Sonic Boom

iTrader: (11)

Depends how many pinion teeth it has too thou.

Rich

ajamesc

You had me worried there drove to work and double checked! ive 41 cw teeth and 11 pinion ones so a 3.7

Sonic Boom

iTrader: (11)

I've got a cheeky little 4.3 to go in my 3 Door over winter.

Rich

ajamesc

how much do you think that will affect your top end or dose that not worry you

Sonic Boom

iTrader: (11)

According to my calculation it'll bring it down to 149mph @ 7500rpm in 5th.
But for Hillclimbing purposes nothing over 120mph is really necessary in a Saloon Car.
Might be blipping the limiter in 5th down the back straight at Donington thou

But it's hillclimbing that counts

Rich

ajamesc

I did think about a 3.9 as my mate has a saff with a supra 3.9 and an elite box. The 3.9 did make a big difference but I'm thinking with the power im going for and twin scroll I should be good with out changing the gearing. And I'd like to do a top speed run in it

Mark V8

iTrader: (2)

You could always use a T56 with a 4.3 diff
Click the link below
T56 with 4.3 diff

Rod-Tarry

Its not the ratio but the gap between 5th/6th that is wrong on the T56.
Think of falling off a cliff & hitting your head on the bottom you maybe alright with a V8 but not a YB.
For all Power levels there is an optimum diff ratio between having grip & not having the Power to pull it. For Andy with RWD & 600+bhp it will be a 3.7 as grip with a 3.9/4.3 will be compromised in the lower gears. You don't go fast spinning your wheels even if that looks fast.

Mark V8

iTrader: (2)

With a 4.3 diff the revs drop around 1700 from 5th to 6th, is that too much with a YB ?

I'm only using a T56 for the overdrive and don't really care about top speed too much...

ajamesc

Has anyone fitted this kit them selfs? The top mount that sits on the two housing studs. Do you need to swap the short stud for a long stud and fit a spacer then trim a little off the cooling fins?