Board logo

Suitability of auto box
mike4444244 - 29/12/06 at 09:26 PM

Hi
I'm fitting a 3.5 rover v8 in my locost and have an sd1 5 speed manual box for it, however the car is for my dad and he would prefer an automatic. Questions are... will a borg warner 65 be ok or will i lose loads of top speed cos its only a 3 speed box and has a final drive of 1:1? are there any more suitable auto donors? if the BW65 is the only box available whats the lowest ratio sierra/other ford diff available?
Thanks
Mike

stevec - 29/12/06 at 09:35 PM

I had a V8 SD1 auto it used to cruise at a ton and more all day, and you can boot them in 1 and then manually go 2 and then 3 great fun.
Steve.

mike4444244 - 29/12/06 at 09:40 PM

hi
sd1s had a diff ratio of 3.08:1 or 2.85:1 though... any ford diffs that low, i thought they were all 3.6-8ish:1, bearing in mind that a rover v8 wont rev that high, but will shove out a skip full of torque , if i go auto had i best source a really low ratio diff?
mike

gazza285 - 29/12/06 at 09:57 PM

High ratio, not low. Some Capris had a 3.09 (the 2.8i, and the 3.0S), and Sierras had a 3.14 (don't know which ones though).

MikeRJ - 29/12/06 at 10:25 PM

No, numericaly he would require a low ratio final drive, i.e. 3:1 is a lower ratio than 4:1.

gazza285 - 29/12/06 at 11:28 PM

Apologies for brain fade.

macnab - 29/12/06 at 11:39 PM

wow I'm suprised you can fit the autobox in the tunnel their usually very large.

stevec - 30/12/06 at 12:14 AM

BW65 is quite slim and compact if my memory serves me.Probably not much difference in wieght with the 5spd manual.
Steve.

macnab - 30/12/06 at 12:31 AM

I'll have to bare that in mind, I like auto's aways quicker off at the lights. I have the top half of a rover V8 3.5 + carbs and manifold and was going to buy a rebuilt block and maybe squeaze it into the locost, once i've got it on the road that is...

mark chandler - 30/12/06 at 12:43 AM

I raced landrovers, the ZF 4 speed with lock up in top is the way to go without a doubt.

I tried BW65/66, chysler torqueflite, ZF easily tops on speed of change, gear spacing infact in every respect (much quicker than manual changing)

You will need to throw away the transfer box, these gearboxes live in premium cars so BMW's et al so getting a tail shaft should be easy enough or if you are lucky source one from a V8 sherpa type ambulance.

NB/ I believe they used to race some SDi rovers with the ZF auto box, its that good and strong !

On the other side you can get the auto'ness' taken out of the older 3 speed boxes so you can use like a manual.

Regards Mark

Simon - 30/12/06 at 12:51 AM

Mike,

I had an old SD1 V8 auto in the mid eighties and from what I can remember with the gearing, if you held it in 1st, it would do about 65. Reverse gear ratio is between 1st and 2nd, so you can do about 80 backwards

I have an auto box (don't know which!) at work - I won't be up there till Sun at earliest, but if you like, I'll try and get the dims.

I reckon it'll make for a very relaxed car!

ATB

Simon

mike4444244 - 30/12/06 at 06:18 PM

Hi Guys,
err yeah it will/should fit its a standard book width chassis, it has an extra wide tunnel to cope with the fat a*se end of the v8 though which makes for interesting sized footwells.... hey theres another good reason to go auto
I didnt think of using a zf from a landy, i bet i could get a tail end off one of the endless e class merc basket cases that my dad accumulates!
Thanks guys, oh BTW i dismantled the diff i got ages ago and its a 3.91:1 so no use to me now... any ideas as to a suitable donor, someone said capri? will the driveshafts fit sierra ones?
Ta
Mike

Simon - 30/12/06 at 11:32 PM

quote:
Originally posted by mike4444244
....... i dismantled the diff i got ages ago and its a 3.91:1 so no use to me now... any ideas as to a suitable donor, someone said capri? will the driveshafts fit sierra ones?
Ta
Mike


No, the Crapi (and Cortina/Escort for that matter) has a live axle rather than IRS like Sierra.

The ratios for the Sierra are very wide, the lowest being 3.14 (and those that have them know how rare they are, and charge accordingly). Then the ratios are something along the lines of 3.38, 3.62 and the 3.9 you have. There are also some LSD in the mix. Do a search on here, and you'll find links to very comprehensive Sierra diff ratio listings.

I used Sierra IRS in mine, but I'm in the process of changing that to Jag. Yeah, there is a weight penalty of about 30kgs, but the ratio I've got is 2.88, with LSD, and will cope with about 400bhp

ATB

Simon

akumabito - 31/12/06 at 12:34 AM

quote:
I used Sierra IRS in mine, but I'm in the process of changing that to Jag. Yeah, there is a weight penalty of about 30kgs, but the ratio I've got is 2.88, with LSD, and will cope with about 400bhp


Seems to me that with the power/torque of a v8, a bit of extra weight on the rear wheels would be a good thing, no?

mike4444244 - 31/12/06 at 05:09 PM

Hi
having decided to go down the zf route, is it easier to get a rangy bellhousing and torque converter and bolt it to the front of a bmw box or get the back of a bmx box and bolt it to the back of a rangy box? Also top gear ratio in a zf box is 0.728:1, what diff ratio would you guys recommend (i'm running 14" escort alloys with i presume standard size tyres). I'd like a balance between good acceleration and top speed? i'm thinking of changing the 3.91 diff for maybe a 3.4ish limited slip? any comments?
Thanks for all the help so far!
Mike

Simon - 31/12/06 at 07:40 PM

quote:
Originally posted by akumabito

Seems to me that with the power/torque of a v8, a bit of extra weight on the rear wheels would be a good thing, no?


I don't think it'll present a problem, especially as I hoping to double the bhp at the same time

ATB

Simon