CoachTom

1986.5
5 speed

Is this high for speed vs RPM??? Yes, the odometer is broken, but that is on the task list... The Speedo is accurate checked by GPS.

Just picked this car up, never owned one before, so, no reference to what is normal...

I had tried to find the model of the transmission and the final drive as i do not think this is what a "U.S." model 928 with a 2.20 final drive was supposed to do, but cannot locate either stampings. Any support is greatly welcomed. The final drive cover has a casting number of 928 301 306 and underneath it says 27/11 on the top of the cover plate.

Thanks,
Tom

Mrmerlin

if you look in the owners manual it has a RPM VS gear diagram
compliments of Andrew Olsen
click the link for your manual

https://rennlist.com/forums/928-foru...al-online.html

G8RB8

Looks about right.

Rob Edwards

Looks about right for a Euro with a 2.73:1 rear end, not a U.S. with a 2.20.




What's the serial number on the bottom of the transmission? Should be something like

11G00XXX

or

11G05XXX

Where X's are the serial # of the transmission. The # is stamped on the rearmost lower rib in the transmission case, like so:

G8RB8

My bad, that was the ROW diagram.

CoachTom

Thanks! Guess what I am seeing is that even though i have a "US" serial numbered vehicle, somewhere in the vehicles history, someone must have swapped out the transmission maybe(?) with a ROW model. The Final Drive is integral to the transmission and cannot be swapped individually?The ROW performance curves align with my observations it seems. Appreciate the ROW chart as I only had the US Manual that came with the car.

Rob, nice clean transmission, thanks for the picture. I will verify, but can see already, from my initial inspection, my coverplate is much different as the indents are different where the drain plugs are and there seems to be a wired sensor???

V/T
TMcD

PorKen

Could be the tach is off.

Otherwise, hopefully a 85-86 ROW trans and not a pre-85 2.75 trans!


I've seen a '86.5 with a '79 trans in it.

Leon Speed

Looks about right for fourth gear.

CoachTom

Had a chance to view the stampings tonight on the transmission.

G2811 11G05634

According to the spreadsheet Rob had attached, it should be a 85-86 US transmission, but the speed and gearing are off. Could the "guts" of this transmission been changed or final drive modified? The wheels rotate in the same direction when rotated. Does that indicates a LSD?

Appreciate any speculation or ideas...

Tom

Rob Edwards

Well, at the very least the transmission case that's in the car belongs to a U.S. '86, the 634th made (or thereabouts....). So either your tach is off, or someone switched out the R&P at some point to a different final drive ratio.

The wheels turning the same way is a good indication of LSD.

There were 'only' 434 U.S 86.5 5-speeds, which begs the question of how there were 634+ G28.11's, but whatever. 222 of them had LSD.

What's your VIN #? Someone ought to be able to tell whether the car was originally equipped with a limited slip.

CoachTom

Rob,
Thanks for the run-out of the transmission serial number...

According to the chart you sent, the R&P should be 15:33 and Final Drive of 2.20. I know the Tach is reading correctly as the climb is normal on the gage and associates with engine noise. Sounds and I feel i need to shift one more gear when i am in cruise.

Transmission is kind of dirty and greasy, so if the R&P was changed, it must have been a while ago as the case and transmission is grungy. So either done a while back long before i became the owner as the conditions are typical of the two components or it came from factory that way.

Is there a way to change the R&P to obtain the 2.20 gearing? I am not using the car as a racer or ever will take to the track. This could be the reason the gearing is set up that way.

WP0JB0927GS861872 is the VIN.

Rob Edwards

WP0JB0927GS861872 ? Huh.

PET is confused about that car- it's listed as a US, non-California car, having an M28.44 engine and an A28.07 automatic transmission. However, the option codes include:

I158 - Blaupunkt Monterey radio
M418- Side moldings
M481 - 5 speed manual transmission (!)
M490 - Sound system
M494- Additional amplifier
M533- Anti-theft device
M650- Sunroof.


So the documentation on this car is contradictory. All '86 Automatics are supposed to have the M28.44 engine, while the 5-speeds have an M28.43.

No LSD listed as an option code.

Your next sleuthing step is to get the engine stamp #, it's on a broached pad under the upper radiator hose.

Looks like this:

PorKen

Artsy pic there, Roberto.

Never seen the bottom of that valley; without a thick layer of muck.

Rob Edwards

Hey Ken-

This better for ya?

CoachTom

Will have number later, not at car, but since it seems to be an "automatic" produced car, why would the transmission; G28/11 be geared so low as it seems to be noted with the 15.33 Ring and Pinion in the PET. Could someone have placed a different R&P into the transaxle?

Ultimately, what will be the work around to get the "right" gearing?