Final drive

[CorseChris]

Mostly preaching to the converted I suspect...but I got round to changing the final drive on my car this weekend. Went from a pretty random 2.94:1 to a 3.35:1. What a difference! Well worth the effort.

...only 1 problem so far...driving to work in the 155 this morning (same box more or less) and every time I changed gear, I had flashes of all the internal workings of the box....I need to get out more I think.......

[Steve Poole]

[QUOTE=

...only 1 problem so far...driving to work in the 155 this morning (same box more or less) and every time I changed gear, I had flashes of all the internal workings of the box....I need to get out more I think.......[/QUOTE]


Take two paracetamol :D :D and two pictures, one of each car then ask the wife to pinch you just so you know you're not dreamin ;) !

Hows that supercharger coming on? :D :D

[Swamprat33]

Hi Chris. Nice one mate.

What Box/FD did you use - what was it from?

How hard/how long did it take you.

Cheers

Tim

[chris.richard]

Interesting Chris!
Has this affected the speedo cable drive?
Is 1st gear still useable when moving, or is it too low now?

[Chris J]

Has this affected the speedo cable drive?


I think that always goes at the same speed as the driveshafts?

[chris.richard]

I think that always goes at the same speed as the driveshafts?
It does, but I wondered if there are issues of the drive takeoff from the crownwheel.

[Swamprat33]

Thats not a problem for me as I use VDO speedo with a sensor on front left wheel.

Tim

[Chris J]

Tim

Late Alfa boxes don't have a cable drive, so I'll have to have something similar to your's.

One day?

[CorseChris]

Oooh, questions...

Box was from some variant of 164 24V - don't know quite which. Ratio is 3.35:1 (17:57) The box I acquired was pretty well done for as it had suffered bearing collapse on the input shaft outer bearing, but the output shaft & crown gear where fine. I'm not complaining though - it was free.

I just swapped the two vital parts into my exisiting 12V box so retained speedo drive as before. Swapover isn't too bad really. Hardest part of working on the box is undoing the two large nuts on the ends of the shafts. Next trickiest is pulling/pressing gear clusters & bearings but not too bad at all. Final tricky bit is removing/replacing the main gearcasing while fiddling the gear selector. Finally twigged that the best way is to make sure the box is in reverse, then the lever can be finagled around the selector forks without too much bother. One gotcha....the later output shaft is slightly different to the early ones so you need to use the 1st gear needle roller from a 24V box as well, or the 1st gear jams up when you put the snap ring in place.

Time-wise it took me a days effort to go from start to finish. Didn't do it in the same day 'cos it got too dark to see what I was doing any more, and there is only so much you can do by braille. It would be a longer job if I wasn't able to pull the box without removing the engine of course, but for once I got lucky and had relocated the chassis diagonals so the box can come neatly out the left side after swinging the strut/upright down & out of the way. This is also a brilliant quick way to disconnect the drive shaft from the box - it just pulls straight out taking the drive flange with it - no mucking aobut undoing the CV joints. This worked so well I repeated it on the right side to get the shaft out of harms way. Not really essential for removing the box but asking for trouble when re-fitting.

1st gear is still very usable. Gives a max speed of 40mph assuming a 6k5 red line. Theoretical top speed is 150 and motorway cruising is around 3 to 3k5 rpm so pretty reasonable. This is with 225/45/16 rear tyres (24" diameter).

....and work slowly, slowly progresses on the blower installation. Basic blower mounting & belt run design/fab now completed, need to make a bracket to attach one end of the belt tensioner spring/damper unit then it's 'just' the plumbing to do. Not sure quite why, but I seem to think this won't cause me too much trouble. No doubt I'll be wrong about that. I intend installing the blower etc but leaving it un-driven for now, until I can get the car mapped properly under boost. I suspect trying to do a DIY map would be pretty risky. I was hoping to be able to do a quick reference power run aspirated, then another with a flappy AFM fitted to try and answer that old question about how much power they cost, then reconfigure the plumbing to include the blower, pop on a longer drive belt, stand back and think happy thoughts........

[Marmott]

So you are there now
I should imagine its transformed the car and engine sound, throttle response etc

As you know I think its the right compromise and still gives a good first gear, it even gives enough traction to question the need for a lsd on a road car.

Pleased you have done it, now there are one or two suspension mods needed to match it..........

[CorseChris]

So you are there now
I should imagine its transformed the car and engine sound, throttle response etc

As you know I think its the right compromise and still gives a good first gear, it even gives enough traction to question the need for a lsd on a road car.

Pleased you have done it, now there are one or two suspension mods needed to match it..........

It's much improved Gary - thanks for nagging me to do it ;) Still not quite sure why I put that 2.94 ratio in there, it's not as if you hadn't already told me what to put in it.

I suppose the 6 speed box is the ultimate solution but this will do me for now. I might find I'm testing the traction once the blower is fitted, but that's a problem for another day.

....suspension mods eh...tell me more!!