Hello guys! I'm trying to find out what type of ratio the rear end of my car has. I can't find the type numbers anywhere on the tubes. I've counted the number of tooth (or cogs, don't know how Americans call them), on the pinion wheel there are 14, on the ring gear wheel 43. What ratio is this?? It's not a posi by the way. This is for a 12 bolt rear end El Camino with TH400.

By the way, a while ago I've posted a topic that I can't get the carrier out of the housing. Seems the bearings are stuck. Even with a prybar under the carrier bolts I still can't get it out!! PLEASE HELP :-(

43/14 = 3.07

Oh I'm embarrassed that it's that simple!! Thanks Sandy!

On the highway the car makes quite a lot of revs (don't now exact, I don’t have a tach) when driving about 100 KMH (60 MPH).

In general, is 3.07 a 'short' ratio??? What ratio would be more suitable for me?? I only do street driving and cruizin', no drag strip stuff. But a bit more speed on the highway without to much revving would be nice :-)

The 3.07 gear would be considered as a "highway" ratio.

Something like 3.73 would be considered a good street performance ratio giving good accleration from a start.

If you want to reduce your engine rpms especially for highway and are not too concerned about takeoff performance then a ratio in the 2.7 range would be good.

You may want to consider an auto overdrive tranny.

As far as getting the ring gear carrier out, I would persist with the bar, just be careful not too damage the differential cover seal surface. Try to lever ie pull straight out and not at an angle.

Not to make you sound dumb, but you do have the axles removed don't you? The differential will not come out with the axles installed. It has happened before. To remove the differential the bearing caps must be removed and the axles must be removed. The differential sould come out after that. I haven't seen a stock differential with the original bearings that was hard to remove. Most of them will fall out because of bearing wear.

yeah and its scary how easy those axles come out, doesn't make ya feel safe when ya take turns. in case you didn't remove them all u have to is remove the spider gears, push in on the wheels, and the clips fall out, and the axles slide right out.

hmm, yeah a 3.07 is the highest ratio you wanna run with your needs. Thats what i have in my 68 chevelle. i have the same tranny and the same rear-end, and i do 2600 rpms at 65mph. If you really want mileage just go with a 2.54 , that will help you out in the mileage depot

Thanks guys. No the axles are out thank god I'm not that stupid hahaha! Also the spider gears are out but the carrier won't come. I'll just try some more with the pry bar.
Seems that I've made a mistake counting. The pinion has 13 teeth so that makes a ratio of about 3.31 is that possible?
Is the difference between 3.31 and 3.07 big?

Just a simple ratio of 3.31 to 3.07 which is about 7.8 percent.

Gerard,i changed fro 3:07 to 3:31 in my 12bolt 69 ss 396 with 4spd and it really woke that thing up for such a small ratio change. It also helped to reduce excessive the shifting from 3rd to 4th back to 3rd then to 4th aqain in slow 35-40mph traffic.

But it seems like from what you stated about having high revs @ 60mph that you want to gear it to turn less rpms at higher speeds in the NETHERLANDS so i would opt for a 3:07 or 273 gear ratio. Anything less than 2:73 like 2:54 ratio will really degrade your lower speed perf if you care about that.

With a 26.5 inch tall tire on my car with 4spd i turned the following rpms @ 60mph with 3:07 & 3:31 ratios and an apporx est for 2:73 ratio.

3:07 -2400 rpms

3:31-2600 rpms (yes i changed to correct speedo gear in trany for 3:31 ratio)

2:73- estimate of approx 2100-2150 rpms.

What are your speed limits (MPH) in the Netherlands and what speeds are you going to be crusing at the majority of the time?

Scott

Hi Scott. The problem is I don't know the exact RPM @ 60 MPH but it feels (sounds) like the engine is revving quite high. Speedlimits depend on type of freeway but mostly max 75 MPH. When cruising about 70 MPH would be nice with not to much rpm.

If you say a small step like switching from 3.31 to 3.07 makes a big difference, I think that would be the best. Switching to 2.73 will be to big I think??? Because I also want to compete at the traffic lights with those punks in Honda Civic's ;-)

What top speeds do your cars have and @ what RPM? I'm talking about normal street cars with about 350-400 HP
Thanks

Have you thought about installing an overdrive transmission? That would give you the best of both.

Do you have a GM original equipment cooling fan ?

Is it possible the fan is failing to "free wheel". These fans can make your engine sound like an airplane even at lower speeds if not functioning properly.