Looking for 4.09 or 4.27 diff gears to Ford 7.5" rear end
Discussion
Hi,
Why does it feel low on power? Should in not be the other way around? Higher gearing more acceleration?
My idea is that I have very limited use of speed in access of 100mph but I have plenty of use for fast acceleration. :-)
With my setup the calculator commes upp with the following for 5th gear (0.82:1):
Wheels 225 x 40 x18
Gearbox: Ford Type 9 with standard gearing
1 2 3 4 5
3,36 1,81 1,26 1 0,82
3.64:1 Original
1000 RPM 25 mph
3000 RPM 75mph
4.09:1
1000 RPM 22.3 mph
3000 RPM 66.8 mph
4.27:1
1000 RPM 21.3 mph
3000 RPM 63.9 mph
Is that too high gearing?
Kind regards
//Rob
Why does it feel low on power? Should in not be the other way around? Higher gearing more acceleration?
My idea is that I have very limited use of speed in access of 100mph but I have plenty of use for fast acceleration. :-)
With my setup the calculator commes upp with the following for 5th gear (0.82:1):
Wheels 225 x 40 x18
Gearbox: Ford Type 9 with standard gearing
1 2 3 4 5
3,36 1,81 1,26 1 0,82
3.64:1 Original
1000 RPM 25 mph
3000 RPM 75mph
4.09:1
1000 RPM 22.3 mph
3000 RPM 66.8 mph
4.27:1
1000 RPM 21.3 mph
3000 RPM 63.9 mph
Is that too high gearing?
Kind regards
//Rob
Hi,
The Power band starts at 2500 and gets going from 3000 RPM with my cam. The Engine is built to run to 7500RPM but is limted to 6500RPM to be safe.
I use for just having fun on a nice day and the occational trackday.
Non of the track we can use for "club events" ar tall enough to reach over 120mph so the fastes will be at the end of the finish straight or on the highway. The latter being limited to 75mph at the most.
There will be some noise on higway use but I can live with that.
That should work?
Kind regards
//rob
The Power band starts at 2500 and gets going from 3000 RPM with my cam. The Engine is built to run to 7500RPM but is limted to 6500RPM to be safe.
I use for just having fun on a nice day and the occational trackday.
Non of the track we can use for "club events" ar tall enough to reach over 120mph so the fastes will be at the end of the finish straight or on the highway. The latter being limited to 75mph at the most.
There will be some noise on higway use but I can live with that.
That should work?
Kind regards
//rob
sebackman said:
I use for just having fun on a nice day and the occational trackday.
I was imagining you wanting to optimise this for performance in the 0 - 100 mph range with no other constraints. But if you plan to use this for touring and cruising, you might find this very low gearing gets uncomfortable when you're pootling along at 60 - 70 mph. If it's not too late, you might want to figure out what revs you expect to be cruising at with the new diff ratio and try driving 20 - 30 miles at similar revs - it'll probably mean dropping down a gear or two. Are you going to be comfortable with that as your top gear?Edited by GreenV8S on Saturday 27th May 18:05
Dear all,
I have now done about 5-600km’s with the new 4.27 diff and I must say that it is the best and cheapest performance upgrade I have done to date.
She runs 63-64mph at 3000 rpm’s which is fine for highway and gives really nice acceleration trough the gears. It is so much more fun to be in power band with without always drop to first or second gear. Well worth it and highly recommended unless you do long stints of mostly high speed highway.
Top speed should be about 120mph and is more than enough on the track straights over here.
I had a 3.64 RS500 diff with a uprated LSD installed before. Now I bought a 1997 Scorpio (frog eye/face lift) diff from a 2.0 autobox car with 4.27 gearing and moved over the LSD unit. The Scorpio diff had done about 100.000km’s but was in very good shape. I guess the smallish 2.0 engine and the autobox is pretty light on the diff.
On word of cation is that the newer diff housing are wider than the std Sierra diff. Interior, mounting and flanges are the same but some of the outside reinforcements on the case needs to be taken down to fit within the Sierra diff cradle in the TVR. Please see picture.
Kind regards
//Rob
I have now done about 5-600km’s with the new 4.27 diff and I must say that it is the best and cheapest performance upgrade I have done to date.
She runs 63-64mph at 3000 rpm’s which is fine for highway and gives really nice acceleration trough the gears. It is so much more fun to be in power band with without always drop to first or second gear. Well worth it and highly recommended unless you do long stints of mostly high speed highway.
Top speed should be about 120mph and is more than enough on the track straights over here.
I had a 3.64 RS500 diff with a uprated LSD installed before. Now I bought a 1997 Scorpio (frog eye/face lift) diff from a 2.0 autobox car with 4.27 gearing and moved over the LSD unit. The Scorpio diff had done about 100.000km’s but was in very good shape. I guess the smallish 2.0 engine and the autobox is pretty light on the diff.
On word of cation is that the newer diff housing are wider than the std Sierra diff. Interior, mounting and flanges are the same but some of the outside reinforcements on the case needs to be taken down to fit within the Sierra diff cradle in the TVR. Please see picture.
Kind regards
//Rob
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