5 Speed conversion

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EggUK

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During the course of planning my E9 csi restoration, I had contemplated upgrading to a 5 speed g/box. I've now been offered a possible suitable g/box, minus bell housing.

The g/box offered is marked up as 262.0.0510.90 on the casting along with 225 1.3 underneath.

My questions, well do you guys know if the bell housing from my existing g/box will fit this new one. And then theres the mechanical drive for the speedo, am I right in thinking that this g/box, either has the drive or the function to allow me to transfer the exisiting mech drive from my 4 speed to this new box ? ...

Is this conversion really as a dramatic improvement as I read about.

Many thanks in advance ...
 
EggUK said:
Is this conversion really as a dramatic improvement as I read about.
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That depends on the sort of driving that you do and the differential gearing supplied with your car. My own experience involves my 1970 2800CS, driven mostly on California freeways at 80mph. The 4-speed was poorly-suited to that combination of gearing and speed; adding an overdrive box really makes the car more relaxed.
 
jmackro said:
That depends on the sort of driving that you do and the differential gearing supplied with your car. My own experience involves my 1970 2800CS, driven mostly on California freeways at 80mph. The 4-speed was poorly-suited to that combination of gearing and speed; adding an overdrive box really makes the car more relaxed.
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Have you figured what your gas mileage is with the 5-speed. I get 17mpg with my 4-speed. Planning on doing the 5-speed swap for better fuel economy. My 5-speed 2002Tii, Vern, gets 30mpg on the highway. Hoping to get 25 mpg with Athena after the swap.
 
adawil2002 said:
Have you figured what your gas mileage is with the 5-speed. I get 17mpg with my 4-speed. Planning on doing the 5-speed swap for better fuel economy. My 5-speed 2002Tii, Vern, gets 30mpg on the highway. Hoping to get 25 mpg with Athena after the swap.
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I am sure that has a lot to do with the engine, any modifications, carburetors, differential gears etc. I get about 20 on the highway with my 5 speed.
m30b34 weber 32/36, 3.64 LSD diff.
 
adawil2002 said:
I get 17mpg with my 4-speed. Hoping to get 25 mpg with Athena after the swap.
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That sounds optimistic. The overdrive 5th has a ratio of about .8 to 1. So if your engine is running 20% slower than it used to, your new fuel economy should be about 17 / .8 or 21mpg. Yea, I know, it isn't that simple: the engine is now operating at a different point on its speed/power/economy curve. But it's a good first approximation.

Improving the fuel economy from 17 to 25 mpg, with just a change in gearing, would require an overdrive ratio of .68 to 1.

I have no idea what the fuel economy is on my own 5-speed equipped 2800. I know it isn't great.
 
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25 mpg is optimistic unless you also shorten the miles in your state.

That leads me to another oddball concept I am promoting after measuring mpg driving the M5 on Hwy 17. It turns out that I can getter better mpg on a hilly road like Hwy 17 than on a flat road, which sounds counter intuitive. Imagine a road that slopes up 15 degrees for half its length and then down 15 degrees for the other half. The mpg on the way up is not likely to be half of the flat road mpg because of all the engine losses that are common to both slopes, lets say it is 20% worse, and the mpg on the way down is almost infinite if you coast in neutral so the average is better than the flat mpg.

I am running in November on a planck of undulating highways and flat taxes! This is the easiest way of improving the national mpg!

The fallacious part is of course that you need to travel a longer distance when you go up and down between two points of the same elevation than through a flat road, but when did fallacies distract politicians? By having undulating surfaces we actually have more linear distance in our state and more land area to build, live, and be taxed on. A win-win.
 
+3 mpg is worth it to me, at least my mpg would be better than a 1992 V8 Chevy Suburban. Not sure what my rear end gearing is, I have a stock '73 CSi built in '72.
 
I currently get 18.5 mpg on the highway with triple Webers and 4 speed. City is maybe half of that or less. My next project is the 5 speed, hopefully for a little better economy but more importantly less wear and tear.
 
Ok, so after doing a little research things are becoming clearer ...

This is a 265 g/box, but casing is marked as 262, the 3 section casting denotes it as a 265 ? They used same casting of the front section as 262 4 speed hence the number on case ?

Now my 2nd question, is this a dogleg CR or an overdrive, is there anyway to tell ? Does the 225 1.3 denote anything ?
 
How to tell... umm, shift it. You don't have to install to try this. Just keep in mind that when you push the shifter forward in the ****pit, you'll be moving the gear selector on the trans to the rear, because of the ball pivot arrangement. Rotate the input shaft any way you want, and try a couple positions. For the adventurous, you can verify the gear ratios this way too.
 
Has anyone had a rebuild or 5 speed conversion by Metric Mechanic. They claim to have a new improved "Ultimate" replacement. What differential gearing is best for 80 mph cruising speeds?
 
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Paulo said:
Has anyone had a rebuild or 5 speed conversion by Metric Mechanic. They claim to have a new improved "Ultimate" replacement. What differential gearing is best for 80 mph cruising speeds?
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I’m a little skeptical. You are either getting a G265/5 or a G265/6. The G265 was offered on other cars so I’m sure other ratios are out there used and new. There are some places like gr-box.sm making custom ratio and FIA homologated 265/5’s.

I don’t have any personal seat time behind a G265/5/6 but the experience is highly documented. Plus there is that thing called math which I tend to rely on too heavily. The 265/6 already works great with several e9 diffs, and the 265/5 is really no different than a factory 260 as far as final drive.

The G265/6 input shaft bearing is special and NLA. There have been some efforts on mye28.com to repro it but I don’t think anything has come to fruition. Someone mentioned a facebook seller last year but their knowledge of G265’s seemed awkwardly missing. Perhaps the folks in Europe have a working solution that I’m unaware of. When you are investigating a ‘rebuilt’ box, ask for specifics on the work. My guess is all new seals and as-needed synchros with an original . The 265/5 bearing is available new, and doesn’t have the extra lip on the race.
 
Currently in process of installing the 5 seed. Carl Nelson's article is detailed and good advice. The biggest issue is balancing the shorter drive shaft very few drive line shops (near where I live) can balance the shafts using the flex coupling. Actually pretty straight forward conversion.
 
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