Transmission swap

[Montzzz]

What’s the main reason to do a transmission swap from 4 speed to 5 speed?

I have a 1971 521 with a 4 speed and just trying to learn the do’s and dont’s, and how to add a bit more power to it. 

[Crashtd420]

10 minutes ago, Montzzz said:

What’s the main reason to do a transmission swap from 4 speed to 5 speed?

I have a 1971 521 with a 4 speed and just trying to learn the do’s and dont’s, and how to add a bit more power to it. 

 

4 to 5 is simply to lower the rpms when on the highway..... if short drives its not a big deal but I lf always traveling a distance its nice to bring the rpm down.... 

I think at 65 in 5th I'm turning around 3200 rpm vs 3600 or 3800 in 4th..... 

Something like that....

[Crashtd420]

It's a nice upgrade if you drive the highway alot....

 

As for power a weber 32/36 with a nice exhaust is always the best and cheapest place to start.....

 

If you have a heath budget then more ideas are available such as cams and side drafts but that has more needs to consider rather than simply bolting something on... 

[datzenmike]

If you drive a lot of highway miles an over drive 5 speed will lower your cruising RPMs 12% to 25% depending on the transmission selected and can slightly increase your mileage. If you live and work in town 5th won't get much use. A 5 speed will not give you more power as the engine remains the same, nor does it allow you to 'go faster'. The L16 (and most gas engines) makes it's power by revving up and has to push the air out of the way at highway speeds. It's top speed might be 80-85 for example so lowering the RPMs at this speed will lower the HP output and with less power to push through the wind resistance the vehicle will slow. 

 

Use 4th on windy days, climbing hills or passing. Fifth was not intended for accelerating but only to lower engine speeds at cruise speeds on the highway. 

[Montzzz]

3 hours ago, datzenmike said:

If you drive a lot of highway miles an over drive 5 speed will lower your cruising RPMs 12% to 25% depending on the transmission selected and can slightly increase your mileage. If you live and work in town 5th won't get much use. A 5 speed will not give you more power as the engine remains the same, nor does it allow you to 'go faster'. The L16 (and most gas engines) makes it's power by revving up and has to push the air out of the way at highway speeds. It's top speed might be 80-85 for example so lowering the RPMs at this speed will lower the HP output and with less power to push through the wind resistance the vehicle will slow. 

 

Use 4th on windy days, climbing hills or passing. Fifth was not intended for accelerating but only to lower engine speeds at cruise speeds on the highway. 

Someone is selling the 5 speed dogsleg

[datzenmike]

It's an ok transmission for an L16 but don't care much for the reverse above first shift pattern. Again if not driving on the highway much this is a lot of bother and expense for an old used 5 speed. Don't throw away any removed parts.

 

R...2...4

1...3....5

 

Fifth is 14.6% over driven. The 521 ratios are what's called a wide ratio with a quite low first gear (3.657) to make take offs easier with a load. The dogleg is more of a mid ratio with a 3.382 first. It'll be fine for regular transportation. As both the F4W63 4 spd and the FS5W63A as similar I think the 521 speedometer gear will fit the 63A and keep the speedometer accurate.

 

The car dogleg is the same length as your 521 4 speed but you will need to modify your transmission mount.

 

 

The driveshaft on the 521 has a bolt in spline...

 

 

It will fit into the dogleg but there is no threads for the nut. Without the nut oil will seep past the splines. Seal the end with a 40mm engine core plug and some sealler...

 

 

If the dogleg comes with a release bearing and collar don't use it, but keep and use your 521 collar that matches your clutch. They came in different lengths keep your 521 collar. Put a new bearing on it though.

 

 

If it comes without the collar and a clutch arm just use your 521 arm.