Low ratio differential

[V_Mad]

I am looking at an option of putting a 3.7:1 diff in my rear axle. Someone suggested using a Hunter axle, which seems a good idea, and I have located one already from a Hunter Eestate car. But on Googling the axle ratio, I found that the 3.7 axle only seems to appear on the Hunter GT, whereas the other Hunters seem to have a 3.89 axle, so I think its not going to be so easy to find a 3.7 one. Am I correct or are their other cars, for example the Arrow range Rapier/Alpine with the 3.7 ?

 

[RootesRacer]

Look into automatics, I would think all the later arrows with automatic would use a 3.70.

 

[Series3Scott]

Chris - a number of us, including myself, have purchased and installed the brand new 3.70 gearsets from Rootes Post Vintage Spares in the Netherlands. Works great and highly recommended for fast cruising on the motorways (especially with an overdrive).

 

[V6 JOSE]

Hi Chris,

If you put the 3.79 gear set into your Alpine, you will be killing some of the performance. The best gear set for the conversion would be a set pf 4.22's. These lower gears would increase acceleration, yet with the overdrive transmission you have, would cruise great on the motorway. The little 2.8 is happiest when it is above 3.000 rpm.

Jose

I am looking at an option of putting a 3.7:1 diff in my rear axle. Someone suggested using a Hunter axle, which seems a good idea, and I have located one already from a Hunter Eestate car. But on Googling the axle ratio, I found that the 3.7 axle only seems to appear on the Hunter GT, whereas the other Hunters seem to have a 3.89 axle, so I think its not going to be so easy to find a 3.7 one. Am I correct or are their other cars, for example the Arrow range Rapier/Alpine with the 3.7 ?

 

[Jim E]

The MPG went up when I replaced the 3.89 with a 4.22 and it went up a good bit. This is while on the freeway, with the 3.89 gear and OD the car was just way out of the power band at 70 MPH.

 

[Bill Blue]

The MPG went up when I replaced the 3.89 with a 4.22 and it went up a good bit. This is while on the freeway, with the 3.89 gear and OD the car was just way out of the power band at 70 MPH.

Probably due more to the camshaft configuration than anything else.

Bill

 

[V_Mad]

My engine is a stock Granada engine, peak torque comes at 3000 rpm, so its easy to keep the engine revs in that region. I want to get the gearing so that max speed is reached in 4th without over revving, and just use 5th as an overdrive. and I also want first gear to be a bit longer. So a 3.7 axle will help me with all of that.

Its interesting to compare axle ratios from the 2.8 V6 donor cars as they are all higher geared than 3.89, the Capri being the highest at 3.09, and thats no slouch.

 

[V_Mad]

Look into automatics, I would think all the later arrows with automatic would use a 3.70.

Thanks I will look out for that, but I suspect an auto in the UK will be nearly as common as rocking horse sh*t.

 

[husky drvr]

Thanks I will look out for that, but I suspect an auto in the UK will be nearly as common as rocking horse sh*t.

Chris,

Even for a family car?

Interesting.