Vixen diff ratios
Discussion
My Vixen is still running the 3.89:1 Triumph differential that it had when it was new and had 89 Bhp. But now it is running ~125 BHp I feel it would benefit from gearing it down a bit.
I want to keep the differential casing/mounting "original" i.e. Maintaining the existing chassis mounts so this means my options are either 3.63:1 or 3.27:1. Does anyone have any experience of running a modified Vixen with either of these final drive options?
I want to keep the differential casing/mounting "original" i.e. Maintaining the existing chassis mounts so this means my options are either 3.63:1 or 3.27:1. Does anyone have any experience of running a modified Vixen with either of these final drive options?
Depends where the 125bhp is in the rev range..... On the basis it's the original 1600 Kent, then you don't want to go to a 3.27 as engine will rev much less....
especially with 15 inch rims....probably spend most of its time 'off the cam' . 3.63 might be better, depending where you drive.
As a side example, when I built my Marlin (kit car) with a tuned Triumph 2500 lump, the 3.27 was perfect, as it's a long stroke engine and car is fairly light, so
was a good choice. In a 2500 Vixen with 15 inch rims the overall gearing with the TR6 3.45:1 would be about the same as my Marlin for 3.27 with 13 inch rims.
I reckon this would be a bit 'tall' for a 1600 Kent engine.
You can calc engine RPM versus road speed quite easily - I can tell you how.... ask if you want to know.
OTOH, you might consider a T9 5 speeder, it's a straight fit to the engine, I think it's the same length as the 4 speed box, not sure, but it should be pretty easy, perhaps have to shorten the propshaft though. But not if you want to stay original, obviously.
especially with 15 inch rims....probably spend most of its time 'off the cam' . 3.63 might be better, depending where you drive.
As a side example, when I built my Marlin (kit car) with a tuned Triumph 2500 lump, the 3.27 was perfect, as it's a long stroke engine and car is fairly light, so
was a good choice. In a 2500 Vixen with 15 inch rims the overall gearing with the TR6 3.45:1 would be about the same as my Marlin for 3.27 with 13 inch rims.
I reckon this would be a bit 'tall' for a 1600 Kent engine.
You can calc engine RPM versus road speed quite easily - I can tell you how.... ask if you want to know.
OTOH, you might consider a T9 5 speeder, it's a straight fit to the engine, I think it's the same length as the 4 speed box, not sure, but it should be pretty easy, perhaps have to shorten the propshaft though. But not if you want to stay original, obviously.
Edited by RCK974X on Wednesday 27th September 02:15
The horsepower isn't so much of a factor if the engine cannot develop torque to pull the engine with higher ratio and / or you cannot physically rev the engine higher with a higher RPM Limit
I have had a 3.64 and 3.92 with 5 speed in dads Zetec Vixen and in my opinion the 3.92 could actually do with being a bit lower to suit the engine (136hp at the wheels) With the 3.64 fitted the engine would be strong in 1st, 2nd from a standstill but would tail off in 3rd and struggle to make revs at all in 4th. 5th was very overdriven and in the real world you would be constantly dropping to 4th from 5th even on slight slopes. The 3.92 is much better and for more performance with the BGH Geartech box (long 1st gear) the car would be even better with something like a 4:1 ratio.
In my opinion with a 4 sp you should leave well alone. If you want more relaxed cruising then install a 5sp, preferably with long 1st because the std 5sp has a very very low 1st gear.
As it stands the 3.92 is the best diff for the 2.0 engine with approx 160hp (flywheel)
I am sure others can work out what the max theoretical speed would be with a 225/60/15 rear wheel, 7500 rev limit and 1:1 4th gear then a .88 overdriven 5th
N.
I have had a 3.64 and 3.92 with 5 speed in dads Zetec Vixen and in my opinion the 3.92 could actually do with being a bit lower to suit the engine (136hp at the wheels) With the 3.64 fitted the engine would be strong in 1st, 2nd from a standstill but would tail off in 3rd and struggle to make revs at all in 4th. 5th was very overdriven and in the real world you would be constantly dropping to 4th from 5th even on slight slopes. The 3.92 is much better and for more performance with the BGH Geartech box (long 1st gear) the car would be even better with something like a 4:1 ratio.
In my opinion with a 4 sp you should leave well alone. If you want more relaxed cruising then install a 5sp, preferably with long 1st because the std 5sp has a very very low 1st gear.
As it stands the 3.92 is the best diff for the 2.0 engine with approx 160hp (flywheel)
I am sure others can work out what the max theoretical speed would be with a 225/60/15 rear wheel, 7500 rev limit and 1:1 4th gear then a .88 overdriven 5th
N.
Edited by Dollyman1850 on Wednesday 27th September 19:18
I always wondered why my Vixen seamed sluggish even allowing for the current standard build engine. Then I had to have the differential rebuilt last year due to oil seal problems. The guy that rebuilt it pointed out that it was a 3.63 and not the expected 3.89. A previous owner has also advised that the car ran a modified engine at one time and would max out the speedometer with ease. From memory, it pulls 3000 rpm at 70 mph.
So 3.63 with a sensibly modified engine and standard 4 speed were in my thoughts as the way to go for a decent road spec. Understand that the 3.63 is quite rare, particularly with the HD spec used by TVR. Somebody on here will know what the HD bit is; something to do with the bearing supports maybe?
Steve
So 3.63 with a sensibly modified engine and standard 4 speed were in my thoughts as the way to go for a decent road spec. Understand that the 3.63 is quite rare, particularly with the HD spec used by TVR. Somebody on here will know what the HD bit is; something to do with the bearing supports maybe?
Steve
Edited by vicankim on Wednesday 27th September 20:52
I think you can still get a 3.6.Gassing Station | TVR Classics | Top of Page | What's New | My Stuff