Reconditioned diffs

[Patrick]

Hi all

New member here so apologies if this question has been done to death elsewhere.

I want to replace my 3.9:1 diff with a higher ratio, (3.63:1 would do I think) to better match the 2 litre Pinto engine in my Roadster. Other than Rimmers can anybody reccommend other sources of recon Marina/Dolomite diffs around?

Nothing against Rimmers, I just want to compare prices before buying.

[neilryland]

Re: Reconditioned diffs

Why not have a rummage round the breakers 1st, there's still a few to be found.

Would definately agree about 3.63:1, been running one of those for about the last 20 years on my 1500 Hybrid.

Put 4.11:1 on for a while when I overhauled the current one, revved the nuts off it at 60+, took it back off again after a week and threw it away. I do keep a 3.89:1 and a couple of half shafts as spares though.

[paul]

Re: Reconditioned diffs

Hi Patrick and Neil,
I am surprised that you are recommending a 3.63 diff. My Cabrio (Millie) has a Pinto with a 3.62 diff. I have always thought that a 3.9 would be better as it compensates for the bigger wheels.

These are my calculations taken from a spreadsheet. I daresay it will be reformatted to be gobbledegook by the append mechanism.

For the engine speed in rpm the speed in mph is shown for fourth and fifth gear. The gear ratios for forth and fifth are 1:1 and 0.82:1 respectively.

Millie as she is 3.62 diff 195/65 R15 Wheels and tyres
RPM 1000 2000 3000 4000 5000
Gear 4th 1 19.2 38.5 57.7 76.9 96.2
Gear 5th 0.82 23.5 46.9 70.4 93.8 117.3

Millie with 3.9:1 Diff
Gear 4th 1 17.9 35.7 53.6 71.4 89.3
Gear 5th 0.82 21.8 43.5 65.3 87.1 108.9

Sierra donor 3.62 diff 185/70 R13 Wheels and tyres (195/60 R14 are virtually the same)
Gear 4th 1 17.8 35.5 53.3 71.1 88.8
Gear 5th 0.82 21.7 43.3 65.0 86.7 108.4

[b_caswell]

Re: Reconditioned diffs

Most roadsters use 13 in wheels with 70 profile tyre. My hybrid with a nackered 2ltr 6 cyl pulls a 3.27 diff and still cruises at 3grand at about 60mph.Has your car got the 5th gear. As far as other suppliers of diffs, the Dolomite up to the 1850 use the same unit so get a copy of Triumph World Mag from Smiths and thumb through the adverts.You will be lucky if you get an exchange price for a different ratio unit.Rimmers are usually the dearest.

[daniels917]

Re: Reconditioned diffs

Hi Patrick, my roadster has the 2l pinto, and i think a 3.63 diff, running 13 inch rims and 185/70 tyres, it goes like stink, I'm thinking of bigger wheels to rasie the ratio higher as i cant change gear fast enough! if you want to see what it is like give me a shout, i'm only just north of Spalding.

[Patrick]

Re: Reconditioned diffs

Thanks all for some good advice

I am running 14" wheels with 195/60 tyres. I want the car to be more of a tourer than a sprinter hence the search for a higher ratio set up. I do have the 5 speed box but it sound as if the engine could easily still pull 3.27:1.

Ben - Thanks for your advice, I'll do that, is it the case for most exchange units that the ratios have to be the same?

[b_caswell]

Re: Reconditioned diffs

Well yes its the crown wheel and pinnion set that is the tradeable part, But some suppliers may offer a discount for the return of your old unit(if your lucky). Best of luck

[Patrick]

Re: Reconditioned diffs

Hi all

Diff and axle are all now off the car so I am going to renew the spring shackle bushes while I am about it. Good job I checked the diff as the pinion gear is misssing some teeth (just like the owner) so it needs replacing anyway though the crownwheel looks ok.

What would you all reccommend ratio wise then, 3.63 or 3.27 as I would like to get around 22 mph per 1000 revs. Paul do you mind consulting your spreadsheet again as it was a bit tricky to decipher in the forum

[neilryland]

Re: Reconditioned diffs

Personally I'd go for a 3.27:1 as you want around 22mph per 1000 rpm. I'd put that ratio in my roadster if I could get hold of one, I'm more into cruising around nowadays rather than tear***ing around.

With my setup, 185/70 X 13 wheels and 4speed O/D box I get around 22mph per 1k rpm.