Ben

I took the car out for a spin tonight. I stumbled upon a long private road and decided to have some fun.
I only got up to ~ 120 mph because of the passengers on board. I did notice that my engine was at just over 5k rpm.
The speedo is pretty accurate. I tested it with GPS upto 100, and on GPS it was 98. The rev counter is pretty good too. Shifts towards the end of the red on kickdown.
The car has had a replacement transmission in its life, but I cant work out which model it must have come out of to give me the short gearing.
Its approx 24mph/1000 rpm. Apparently I should have 31.25mph/1000 rpm, because its a euro S2 model.
Can anyone shed some light onto this?

C.F.

Its amazing how many of these private roads exist isn't it

'84-'86 euro auto's should have a 2.36 with a 2.54 optional .It is a 4 speed isn't it ? '87> euro autos were 2.54

Ben

Mine should be 2.36, but even with a 2.54, the engine should still be turning less at 120.

RngTrtl

in my 85 auto my tach is right around 4k at 120 mph, hmm.

killingmoon65

I have only had my 78 up to 110 recently and the revs were not yet close to 5k. That does sound high. Hows the trans fluid level? Does it ever give you an engine flare-up around fast hard turns? Just some ideas. I would be interested to know the outcome of this question. I notice when I'm getting up to speed that once in top gear the revs will remain around the same but the speedo slowly increases for another 5-10 mph. I'm not sure what that exactly is but maybe your trans is failing at that. Good luck man.

IcemanG17

That does sound a bit low.....even with the 2.54.....are you sure its in 4th gear....because it sounds about right for 3rd?

C.F.

Remember guys ,you have USA 2.20 gearing for autos ,unless you have a euro & so would by using less revs for the same speed.
928 Specialist transmission specs are below
928 Final Drive Ratio Chart

bigmac

My 90 S4 (2.54) does the 3/4 shift at 122mph.

Ben

Fluid level is fine, I have no flare ups on cornering etc. Does shift hard occasionally under very light throttle, but I know the modulator needs a little tweak.
I thought maybe the trans cable was adjusted badly and it was in third, but I can shift down through the gears manually, and count them back up again on acceleration, and all other positions are where they should be.
Maybe someone put in a 2.73 final in its life? Is this even possible?
I know one of the PO's was a keen performance man... deleted the air pump, AC, Viscous Fan etc...

tv

I have had my 85 euro S2 auto slightly above your speed in 3rd before shifting and mine has the optional A28.06 2.54 tranny. I was next to a diablo at the time.

Ben

Ok, So whats the likelyhood that I only have a 3 speed transmisison installed??
I tried pulling away in position 2 earlier and noticed no shifts. If I do this in my benz, I shift once because shifting to 2 forces a first gear start.

Happy new year anyway!