Gears 1-5 in a 1975 transmission?

[RWebb]

Does anybody know (or have a Tech. Spec. Book handy to look in) to give the gear ratios for 1st thru 5th in a 1975 915 gearbox?


If handy, I have the same question for a 1973 tranny also...

[mark D]

Hope this helps Carrera 2.7
1st 11/35=3.182
2nd 18/33=1.834
3rd 23/29=1.261
4th 27/25=0.925
5th 29/21=o.724

[Bill Verburg]

'75 used 915/40 but were geared the same as later 915/44 & /60

[RWebb]

Thanks Bill -- I'm trying to find out if the 8:31 R&P will eliminate the stump-puller 1st gear I have now with a 7:31 box.

If so, then I'll buy a '75 tranny

[Bill Verburg]

for comparison, using the same rpm limit & rear tire and 1-5 gear sets
a 7:31 will give you ~35, 61, 89, 112, 136

[RWebb]

As I recall from another post, you said to aim for about 40 mph at redline for 1st (right?). Thus, I'd be a lot closer with the '75 box...

I have 15" wheels tho (6s & 7s) with (currently) 205/55ZR-15 SO-3s. I think those are 23.87 inches dia. tires.

Not sure if that puts me closer or further away from your chart.

The '75 box does have the removable guide tube - allowing bench top input shaft seal replacement.

Does the 1975 box sound like a worthwhile purchase to get the different (stronger) R&P, improved seal access, and better gearing??

(+ whatever other concealed improvements they might have made in 2 years but I don't know about).

I think I've found one for about $1,500 delivered and said to be in good shape, but you never know if you are going to be disappointed when you open the package up...

[Bill Verburg]

here's what you are looking at, looks good to me for most purposes, but it also depends on what you are going do do w/ it

[Matt Monson]

Rwebb,
I'll second what Bill is telling you. I think that '75 gearbox will be better for most purposes, including gas mileage which helps a little with today's mile high gas prices...

[RWebb]

Thanks Bill & Matt.

The usage will be for a hotrod - but street only. My thought it that whichever one I have it will have to be regeared, but it appears that fewer additional & expensive gears will have to be purchased for the '75. It looks like I can keep 1st gear, for sure.

[Matt Monson]

Yeah,
You can leave 1st and keep 5th for highway cruising. Then you just replace 2,3,4. Let me know if you want any guidance on ratios. I run gearcharts all day long...