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Gazzab
20-05-10, 09:25 PM
Hi just testing to what type of advert my title brings up....Hi Hi :D
The question is what is the most usable diff I can use in my granny based sumo? I have the doner diff from a 2lt GL auto and first gear (tremec tr3990) is not used as it seems too low. Not sure of the ratio of this diff tho. Engine 350 sbc about 316 bhp, I would like a more usable 1st gear any ideas? Also is it worth going lsd? Just for good measure I like to keep a Breast of things !!!:D

Gary

Purple AK
20-05-10, 09:31 PM
Hi just testing to what type of advert my title brings up....Hi Hi :D
The question is what is the most usable diff I can use in my granny based sumo? I have the doner diff from a 2lt GL auto and first gear (tremec tr3990) is not used as it seems too low. Not sure of the ratio of this diff tho. Engine 350 sbc about 316 bhp, I would like a more usable 1st gear any ideas? Also is it worth going lsd? Just for good measure I like to keep a Breast of things !!!:D

Gary
British American for me :???: :-D

Gazzab
20-05-10, 09:39 PM
British American for me :???: :-D

Thanks Chris

Do you mean as a supplier of ford diffs? info etc

Gary

GaryV35
28-05-10, 01:00 PM
I would look for 3.36 diff. I got mine from a scorpio diesel. The rear diff cover was different as well as the output flanges but swapped these from the 3.92 (I think it was) that came with 2lt Granada donor car. I've now got a useable 1st gear and much lower revs when cruising

nuf_said
28-05-10, 06:31 PM
Hi just testing to what type of advert my title brings up....Hi Hi :D
!!!:D

Gary

I feel like a Big Tit.........

An advert for Mazda MX 5 came up on mine..

Nuf Said

Gazzab
28-05-10, 09:06 PM
I would look for 3.36 diff. I got mine from a scorpio diesel. The rear diff cover was different as well as the output flanges but swapped these from the 3.92 (I think it was) that came with 2lt Granada donor car. I've now got a useable 1st gear and much lower revs when cruising

Thanks for your input Gary was hoping to get a limited slip jobbie not sure if the scorpio has that option on a diesel but a useable 1st gear would be good and lower the cruising revs also.

And Nuf Said about my tittttttle!!!!!!!!!!!!!

Gary :-D

Sidecarbod
28-05-10, 09:38 PM
The problem with messing about with the diff ratio in order to get a decent length first gear is that you could end up messing up the other ratios, especially top gear. If the top gear ends up being too tall the car won't rev out in top. This may or may not be important to you.

I have tried 3 different ratios in my sumo. The first diff was an open 3.62. With a crappy 3.5 engine it would not rev out in top, I could thrash the nuts off it in fourth, shift into top and all that would happen is the revs would drop but the speed remained the same. The engine made about 180 BHP.

I then bunged in my 4.6 lump which makes about 285 BHP, the car was now undergeared, it would rev out in top very easily, the problem was that at cruising speed the revs were quite high when they did not need to be. The wheels also spun like mad in second gear so I bunged in a 3.64 LSD. The ratio was virtually the same, both rear wheels now spin at the same time rather than just one. First gear is now useless I never use it.

I then fitted an open 3.38 diff, this has dropped the revs by about 400 RPM at 80 MPH, the car should hit 145 MPH if the motor can pull the taller gearing. I've only got the thing to rev to 5K with this setup so far, the last 500 RPM is worth about 15 MPH. It might pull this or it might not. First gear is still useless! I am fitting a 75 BHP NOS fit so the bugger will rev to 5500 or even 6000 when I hit the button. :p

I think that I will keep the 3.38 diff and convert it to an LSD using the bits from my LSD diff. You also need to be careful when buying diffs because there are two sizes of flanges as well as two case sizes. There are ways round these problems though.

I would go for an LSD, my is not fitted at the moment and I don't trust the back end that much, its "loose" :confused:

Really to work all of this out you need to know the ratio's of your gearbox so that you can compare at least first and fifth to my box for example.

Noel has a 3.64 diff with a tremec, his first gear is usable, I won't want to be anywhere near the thing if it revs out in top!

My first gear is 3.321:1 my fifth gear is 0.77:1 or 0.79:1 (Depending on which website I look at!).

HTH,

Pete