Avenger Diff ratios to give better top speed?

[JoKer]

my spare diff is 3.89, check build thread for cool 200kph + run

[avenga]

I saw that. Man your new engine is quick. 0-200KPH in only a few seconds.

You should switch to a 4.11 for rally use, gives you better acceleration but kills top end a bit.

I could pull 200KPH down the back straight of Pukekohe flat out in top with my 4.11:1 diff.

[oldschool]

Yes I thought the speed was a bit high for the RPM, as the manual says the 3.70:1 does 28 km/h per 1000 rpm = 3571 rpm @ 100 km/h on standard 155/80-13 tyres, which is 3474 RPM on my 165/80-13 tyres.
My tacho is probably accurate, so my speedo is probably reading 10 to 15% high, like Scarletts....lol

[avenga]

Yup, as I said. the tyre swap drops the engine revs by around 100RPM so 3474RPM@100KPH sounds right.

I was getting around 3,500RPM@100KPH on my 185/70/R13 tyres which is a 5.5mm increase in tyre diameter. 165/80/R13 are a 8mm increase so 3474RPM@100KPH would be spot on.

But the 3,000RPM@100KPH you said before is way too low for any tyre/diff combo you could get away with. They only way to get that low is a gearbox or diff conversion.

[oldschool]

Yeah, I know when we went to Palmy, Scarlett was reading 56 km/h when those speed displays on the side of the road said I was doing 50 km/h, so that's 12% fast, even with the 175/80-13 tyres! If the GLS is similar, it will read about 15% fast with the 165/80-12 tyres, so a real speed of 86 km/h @ 3000 RPM...lol
We'll have to check it with your GPS speedo.

[avenga]

Yeah 3000RPM@86KPH is about right.

I will just find the cigarette lighter power adapter for my GPS speedo and we can take it for a test run. Once you know what the revs are at a certain speed then you can just use the rev counter to tell how fast you are going. I used to do that before I got my GPS speedo, I knew 3,500RPM was about 100KPH so on the motorway I would just make sure I stuck to under 3,500RPM

[azza1600]

Intersting guys, but my GL is no way doing 3500rpm at 100k, mine is doing 3200 and that is what it was doing when a copa did me for doing 100 in a 80..and I did see his dash mounted display....and by the way them road side speed displays are full of shit...didnt you see target lol

[avenga]

Yours is a late model so it would probably have a 3.70:1 diff. What size tyres are you running? I could do the math to work out what the revs should be at 100KPH.

I agree those road side signs are crap. My gps speedo is really accurate and I find those road side signs are all over the show. If they even pick up my car at all.

[oldschool]

I just put a couple of Sierra 14" x 5.5J wheels and 175/80-14 Kingstar H714 (Hankook) tyres on the back of Logan's car to improve the gearing, as Avengers rev like crazy on the highway...lol
An Avenger 1600 (3.89 diff) with standard 155/80-13 tyres does 3550 rpm at 100 km/h
With the 175/80-14 tyres that drops down to 3250 rpm, a big improvement!
Even better for a 1300 or Wagon with the 4.11 diff, revs drop from 3750 to 3400.
Speedo should still be okay as they read fast anyway.
The front is running standard 13" rims with 165/80-13 tyres.
Has a nice raked (Starsky and Hutch) look with the 13" on the front and 14" on the rear.

I have more 14" Sierra rims for $40 each if anyone one wants them?

[avenga]

Awesome. Love the cop rim look.

It would look pretty cool raked. I do that on most my cars. My charger is 245/60/R14 vs 215/60/R14 and my '75 Avenger will be 225/50/R15 vs 205/50/R15.

[oldschool]

Yeah, the cops have no chance of catching Logan now...haha
An easy mod as the Sierra offset is the same +40, so the tyres tuck under the guards nicely.
175/80-14 is normally a commercial 8 ply tyre - too stiff for a car.
The 4 ply Kingstars are excellent, cost $93 each fitted and balanced.

[JoKer]

Just done Diff swap from late Model Chrylser Avenger Sedan, no motor or dash so no idea what size it was

musta been 3.89:1 / same as what I had as the 100kph speed : revs are the same

then I saw this on Instagram




www.instagram.com/p/BJmZq35jEpt/

something about a Dana 30 in an Avenger diff in Brazil

now that's something to look into I reckon

appears to be a LSD? or locker?

[oldschool]

The chassis tag will tell you if the Chrysler was a 1300 (3.89 diff) or a 1600 (3.7 diff)
The 3rd and 4th figures are 1M for a 1300 and 7M for a 1600.
The 2nd figure is the year..
M=1977/78
N=1978/79
P=1979/80
Q=1980/81