Diesel Swaps into 50s/60s Classics

[oil pan 4]

Depending on the pump the mechanical ones were governed up to 4400 and the electronic DB4 pumps were around 3600.

I have ran into the mechanical governer a few time on my mechanically injected 6.5, since I hand built the engine and had its internals ballanced by a mechine shop I know it can take it.

[lacolocho]

I was saying with a 6.2 you probably want a higher rearend than what would come in a typical 60's era car just because you would waste a lot of gas if your rpms are too high, it probably wouldn't hurt anything and you can even tune the 6.2 to deal with high RPMs fairly well but there is not point to have the gears needed for pulling stumps when the 6.2 in a car can get better fuel economy in the 1600-2200rpm range.

I'm sorry, but this sounds backwards to me.
I thought that a lower-geared differential would bring the rpms down and get better mpg's when just cruising, whereas a higher-geared differential is better for towing, etc.
You seem to be saying the opposite?

[Frank Lee]

It is easy to mix up; "higher" rear ends have lower numerical ratios i.e. a 2.5:1 rear end is a higher rear end than a 4.11:1 rear end. They are called higher because they give higher speeds per input rpm.

[lacolocho]

It is easy to mix up; "higher" rear ends have lower numerical ratios i.e. a 2.5:1 rear end is a higher rear end than a 4.11:1 rear end. They are called higher because they give higher speeds per input rpm.

Gotcha, thanks.
It still seems pretty strange to me that a 60s sedan would have lower rear end than an 80s suburban.

[oil pan 4]

My 2wd sub and its factory 3.08 gears are kind of rare.

In the 90s when every one wanted more pulling and towing power a lot of the 4x4 turbo 6.5L trucks had 3.73 and 4.10 gears, its pretty common for the turbo 4x4 to be down 10mpg from what I get.

[rmay635703]

Originally Posted by lacolocho

Gotcha, thanks.
It still seems pretty strange to me that a 60s sedan would have lower rear end than an 80s suburban.

May seem strange but it can be true, you need to know exactly what car, motor, rearend etc you are dealing with before you can compare apples to oranges.

Like oil pan said his truck (and all (3) of the suburbans I've had over the years) all have had 3.08's stock, mine currently has 2.8's just because that is what was cheap at the junkyard the day.

Suburbans typically have 3.08s-4.56's depending on what paticular one you are grabbing from.

It is worth noting that in the "antique" days a rather large range of gears were possible, anything from 2.5's-5.xx's, I have even seen 6,7,& 8s on some trucklike vehicles.

Back then most manufacturers were more interested in haveing the car cruise in a nice torque band, this meant that you might be buzzing down the road in 3rd gear at 3500rpms on the highway.

This obviously wasn't always true but it wasn't uncommon either. There were some manufacturers that geared for economy but many also did not.

Cheers
Ryan

[oil pan 4]

Originally Posted by rmay635703

mine currently has 2.8's just because that is what was cheap at the junkyard the day.

I would love to have to have a 2.83 rear on my suburban.
With the weight reduction I have done and in the process of doing and putting the turbo on it would work really well.
The holset HE351VE turbo is an 86mm turbo that lights off nearly instantly (little turbo lag).

I bet the local junk yard would love to unload a seemingly usless and utterly unwanted 2.83 or 2.93 rear end for next to nothing.

With 2.83s I would consider a smaller tire. For me the load rating is most important.

[lacolocho]

So what gear ratios are common on the 60's cars?

[oil pan 4]

It depends on the transmission.
The less gears the cars transmission has the lower the rear end gear number is likely to be.

[rmay635703]

Originally Posted by lacolocho

So what gear ratios are common on the 60's cars?

LoL, depends on what car and what motor, many buick elantras? had 2.5's, other chevys had much lower geared stuff depends on what it was marketed toward, you had a whole rainbow of variety back then.

I would also argue that a 3sp doesn't mean you necessarily have a high rearend, some vehicles top out at 65mph in top, just depends on the motor and size of the car.

The bigger stuff you likely want is much more likely to have airplane gears though