Standard diff ratio for 1976 1600?

[kriemhild]

Well, I know eff all, but I'm learning 

My mechanic reckons I need to find a standard diff for my Avenger to have it run happily at 100 km/h without it screaming. He reckons that the diff I have on it now- 4:1 or something he said- I forget exactly- is not standard and I need a 3.9:1 diff for the driving I'm doing (Canterbury roads, dead flat, lots of driving on the motorways).

Is this 3.9:1 diff -or whatever it is- bog standard and relatively easy to find?

Cheers guys!

[JoKer]

I think Auto's had the best crusier ratio out, my Haynes is at hm will check the list if i rememebr (somethign like 3.7 even

[oldschool]

Nah, autos used the same diff as manuals and they rev higher because of the torque converter slip.
If you're doing lots of cruising fit a Chrysler 3.7 diff, don't bother with a Hillman 3.89 as she'll still be revving high on standard wheels and tyres.

[kriemhild]

I live out in the wops, but drive in Earthquake City daily as well. See nary a hill as it's the Great Canterbury Pancake that I'm navigating here. Do any of you fellows know how hard it is to find either a 3.7 or a 3.89 diff?

[avenga]

3.89 should be pretty easy to find. any Hillman 1600 should have one in there.

For a 3.7 you would have to find a Chrysler.

Try this auction.

http://www.trademe.co.nz/motors/car-parts-accessories/chrysler/other/auction-537716733.htm

By the looks of it, it is a Chrysler Avenger 1600 GLS. That would have a 3.7 unless somebody swapped it. It is in Dunedin so not too far.

[kriemhild]

hey cheers guys. I'm getting to think that a 3.89 and a 3.7 can't be TOO dissimilar- well of course they are, but either has to  be an improvement on the pain-in-the-arse 4.1 or whatever it is now... whatever I can get relatively close to home would be good as I shudder to think about the freighting costs for a diff and rear axle assembly. I can always take a road trip to Dunedin : D thanks again for the info as I had no idea what was out there.

[avenga]

Here are what all the different differential work out to on the road, note not all were available in NZ.

4.37:1, 4,000RPM@100KPH
4.11:1, 3,846RPM@100KPH
3.89:1, 3,704RPM@100KPH
3.70:1, 3,571RPM@100KPH
3.54:1, 3,333RPM@100KPH

I use a 3.70:1 with a 5 speed so I am down around 2,800RPM@100KPH