F13 gear ratios

[Nick Bayntun]

My Opel GSI Mk1 is running a F13 gearbox with a final drive, from my calculations of 3.74-1, Im happy with the ratio of 1st 2nd 3rd and 4th but would prefer to have a longer 5th, I live in a very mountainous place where you rarely get out of 3rd on any A road, but when you hit the motorway I feel like im strangling a cat in 4th and 5th, the current 1.6 lump would pull a longer gear without any problems, I have an engine rebuild planned to add around 35bhp so plenty to pull a longer 5th.

My question, which gearbox will I find a longer 5th and maybe 4th or would I be better off changing the crown wheel and pinion and alter the lot or a completely different box (mechanical speedo)

Thanks in advance, any info would be great

Cheers

[Stuart]

http://slindborg.hostei.com/gears/Overbrenging%20Corsa%20A.jpg

Depending if you have a CR box or not, you can put the 0.71 5th gear in. Otherwise you will just have to get used to the higer revs... Its not an issue, its more that modern deisels rev so sodding low that if you see more than 3000RPM at cruise then people assume its revving its tits off, except thats likely to be less than half of max revs lol

[Nick Bayntun]

Thanks for the info Stuart, where did you find the document, a gem! I will check out the engine number tomorrow, I recon its a E or C16SE which would make it the CR box, I pulled the cluster out a while back to fit a new shaft bearing and counted the teeth at the same time, all the ratios match the CR, which Im glad about anything could have happened in 28 years at least its the original. At this moment my rev counter is not displaying the correct RPM, its over posting can't work out why, at 100K its displaying 6k +/- revs. I have been thinking of buying some new rims only because I can't fine the centre caps for the originals, like rocking horse shit! I guess with the right combo of rim and tyre size I could achieve a greater rolling radius which would help. Thanks again.

[Stuart]

Cant recall where I got them from in the first place, but there are F10-F23 images on my crappy calculator site here http://slindborg.hostei.com/

Wow, the revs claiming 62Mph is 6Krpm... thats mad (unless you are stuck in 2nd lol )
What is it showing at Idle?

[Stuart]

Also, when looking at the gearbox from the wheel arch, clean off the little flat bit just under the sealent line at the bottom, this should have a letter and number stamped in...

E.G C374 which would show its a CR box with a 3.74 FD, this does assume the box hasnt been fiddled with. Saves reopening it :D

[Nick Bayntun]

On a timing light I have around 850 shows 1100, had a right battle setting the idle refering to the rev counter, it wasn't until I put the timming light on it and noticed I was trying to get it to idle at around 700 sounded like my dads lawnmower! Any idea what could be wrong, the rev counter must be getting its signal from the coil there isn't a sensor on the fly wheel.