Hi,

I was wondering if anyone can give me some info - My 5 speed manual Porsche transmission needs to be rebuilt, I was told to up grade to a 1986 928 BW manual transmission. My transmission shop told me I wont be happy. They said " The differences are not big in 1st and 2nd gears, but they grow a whole lot for 3rd, 4th, and 5th. I think you would be giving up quite a bit of the feeling of performance with the ’86 transmission."

Any thoughts? Thanks Peter

 

You transmission shop gave you good advice. One of the best things about the early 928 gearbox is the gear ratios are relatively close, and the final drive is higher (2.73 vs 2.2).
The original G28/03 gearbox fits the early 928's power & torque, top peed & practical speed very well.

 

What if we change the R&P from the 79 trans to the 86 trans

 

That would get you a little farther along, but the gears in the box are also closer on the early ones. Keep in mind, the top speed of the earlier cars was lower, so no need for the long legs of later gearboxes = closer ratio gearbox.

 

Okay - Thanks

 

Based on what you guys provided here, I would guess that putting an 86 trans into one of the 300 HP S cars would be a nice improvement with the longer gears and then won't have to run at such high RPMs on the highway. True, or will that make the very quick feeling S car then feel like an early non-S? My 81 Euro S is very light and quick feeling - almost as quick as my supercharged 79.

 

I've driven an '84 EuroS with a later gearbox w/2.20 FD. It was a very good match.
Keep in mind, the stock '84 EuroS gear ratios are spread out a little more the the earlier ones. Also higher top speed, longer legs.

 

Nice. Thanks Jim.

 

So you think its a good idea to change my 79 Porsche transmission to the 86 Bourg Warner transmission (I'm told the B W is a much better trans) - I'm also going change the R&P from my the 79 and put it into the 86 trans

 

please note that the torque tube and shift linkage are different for 79 and 86 and the R&P is not a direct or easy swap. I only know of one person that made it work

 

I also have the torque tube and the part time diff. out of the 86, I'm not sure if my R&P will fit - I don't want to reinvent the wheel if its too much maybe I should just rebuild the 79 trans? I can always sell the 86 trans - What would you do?

 

No brainer.
Rebuild the '79 transmission.
Done properly, they shift like butter and have the proper gear ratios for your engine/year model.

Sell the '86 to someone who can use it.

 

Thanks for the advice, let me know if you know anyone who needs a 86 transmission - Thanks Peter

 

85 86, and all later model 5 speed boxes are very desirable.

If Mark says its complicated for the very early cars. then its true. And for those lower power units the ratio could matter. Got that. The workshop manual does a pretty good job of itemizing the parts differences, at least major ones.

But putting them into any other mid year car is a wonderful transformation. I've put one into 84, actually Jadz 928 and I did so. When you can't shift gear to gear without grinding, smooth is far better, regardless of other nuances. That 86 we used was from a wreck. It was perfect in 84. Plug and play.

 

Got it, big help - Thanks