4 speed or 5 speed?

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JHGO

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Looking at restored E9 project and have a choice of 4 speed or 5 speed. Mostly in-town driving so 4 speed ok?
 
JHGO said:
dont know...but sounds like a 3:45 diff and 4 speed is ok?
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What's "OK" will vary from person to person. A higher final drive ratio and/or an overdrive 5th gear will reduce noise at highway speeds and perhaps even increase MPG. Drive them both...city and highway. Determine for yourself what is acceptable. Also determine what percentage of your driving will be at highway speeds. If you are big on long distance cruising, the OD might be a good choice. If not, it will not be as important. Also, evaluate all other aspects of the two cars. Only if they are absolutely identical in all other areas would the overdrive become the deciding factor. For example, the amount of rust or repaired rust is far more important than the final drive ratio or an overdrive. Good luck with your purchase. :)
 
If you are looking at finishing a project e9 or having someone do it, you probably should go for the 5 speed. I wouldn't worry about the cost because you will be spending a truckload anyway. :) Anytime you hit the freeway, you will be glad you did. Your car will be that much more desirable if you ever do sell. Oh, and if you are looking at a completely restored car (CS or CSi), chances are the previous owner upgraded to a 5 speed.
 
The quick easy answer may be a 4 speed with a 3.25 differential.
thats a 11% drop in rpm from a USA 3.64 differential.

4000 rpm goes to 3600 rpm

only if your car runs strong and you want to drive like a gentleman…
 
sfdon said:
The quick easy answer may be a 4 speed with a 3.25 differential.
thats a 11% drop in rpm from a USA 3.64 differential.

4000 rpm goes to 3600 rpm

only if your car runs strong and you want to drive like a gentleman…
Click to expand...
@sfdon I didn't know that was an option. Is that an easy swap from my 4sp?
 
Having just gone from a 3.64 to a 3:45 with a 5-speed, I find that 4 gears is plenty if not doing a lot of highway driving. If i shift into 5th at 3k rpm on the interstate, I am already above the speed limit. That said and as mentioned above, a 5-speed certainly won't hurt the value, but the cost difference between the two Getrags is quite a lot these days.
 
hello . I'v been fortunate to have E9 'Bayerisce Coupes' and SalOons since the early 1980s and my Father bought a NEW '72 4spd BAVARIA from Frank Hilson's. MURRAH MOTORS as well.
My objective comment is that the Gertrag 5spd enables significantly enhanced 'Cruising speed' gF NM/FL USA☮️
 
My 2 cents. I love to shift, so the more the better. But really, as others have pointed out, the rear axle ratio and the type of driving one does should be the determining factor. And of course the cost.

My experience with my 70 2800cs, originally had a ZF 4 speed. But even local driving, at times it begged for that 5th gear. So I gave it one.

Jjs2800cs
 
if you want to shift and increase the speed off the line, changing the diff to something like a 4.11:1 will give you a lot more quickness. the e30 M3 used a 4.11 with the 265 - 5 speed and same HP as the coupe ... just a 16v 2.3L 4 cyl. the 4.11 will limit your top end and raise the RPM at highway speeds, but will add some fun for mountain roads. as i remember, Ray Korman used to use a 4.11 in a 2002 race car.
 
I second all the votes for a 5-speed. Besides the decrease in RPMs at highway speeds, and the reduced noise that brings with it, FWIW there is a (marginal) improvement in fuel efficiency at cruising speeds.
 
I think it may be important to note that there are (2) five speed transmissions that may present. A 265/6 (overdrive) and a 265/5 (close ratio). Dramatically different recommendations relative to which 5-speed we're talking about. The latter has the same top gear (1:1) ratio as the contemporary 4-speed. Whereas the former would offer lower RPMs at highway speeds. I am a big fan of the 3.45 ratio with a strong motor. That's the combination I have planned (a 3.45 rear diff with a 265/5 close ratio transmission). Last year I replaced my 4.10 ratio rear diff with a 3.64 rear diff in my 1968 1600. Some would say this is a dog of a ratio, but I appreciate the highway revs. And I don't like shifting into second before I'm through the intersection.
 
My ZF 4-speed was well matched with my 2.8 litre, it rev'd nicely. now that I have a 265/6 I don't miss it. Overdrive is nice on the freeway.
 
If changing diff ratio don't forget will need the speedo to suit. Mine had a 4.10,but a speedo for a 3.25! So at 100mph was doing an indicated 140ish. I do a lot of highway driving so have gone for the 3.25 with an OD 5 speed, although running a bit more power than stock, on a standard 3.0 a 3.45 would be the sweet spot.

I have a 3.07 mated to an OD 5 speed on my Euro E24 and it really wants to be cruising at 80+, find it to be a bit too long geared unless driving on the continent
 
I like the 4 spd in my 2800CS. Running at 80 mph results in the engine rpm at 4,000. That is just purring for that BMW engine. I am sure I would like a 5 speed with OD, but I don't feel the need to go to the effort to install one just to drop the rpm a little. I normally like my vehicles to be near as they were from the factory. I still like restomods, but original cars in great condition really catch my attention.
 
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