I am going to convert my 1986.5 928S track car to a manual. I have a 2:20 LSD manual trans from a 1986 928S and was hoping to swap with someone for a better geared trans for track duties.

Constantine

 

Sterling is looking to swap 87-88 manual w/220 for 85 w/2.73. Could you swap differentials?

 

In manual gearboxes pinion gear is part of pinion shaft meaning it must be changed to make a swap. Can be done of course but requires total dismantling.

 

2.73 is GT or GTS, right? Might be a tall order...
I suspect you want a BW synchroed trans., but I could provide a '82 2.75 trans without LSD.

 

some supercharged guy is looking for this swap. i think he has a euro tranny.

 

IMHO, the choice of transaxle depends upon the target track(s). I've got the '85 2:20 final drive LSD 5-speed transaxle in my '79 Euro track car and it is just fine for many of the local tracks. If you look back to the MANY posts made regarding this topic, there isn't a whole lot of difference between this box and the others with lower final drive except for 1st gear (that is only good for launches, I can break my tires loose anyway) and 5th gear which is a useless appendage for most tracks anyway.

At one of the local tracks I do reach the end of 4th gear in a long "drag strip" straight section and a shifting up buys questionable performance.

I can say that I shift about 1/3 less than my oil/air cooled 6 cylinder Porsche friends. The V8 torque means you don't have to shift, that is probably why Porsche picked the gear spacing - pretty much a 3 speed box for me on the track.

The best choice transaxle would be the GTS unit with an oil pump/cooler. Now if we could come up with a closer ratio "true" GTS 5 speed, that would help. But, there are no such gears available.

Good luck with your upgrade. You have a great track machine, any of the transaxles will improve it.

 

Bah! Final drive means nothing....just ask Kibort

Rich

 

I have a 2:75 LSD 5-speed in my 79 (see signature). I've been thinking about dropping in a 2:20 trans for a while now.

 

The '85 and newer transaxles were Borg Warner sourced and are said to have much better synchronizers and were beefier then the previous generation Porsche "crash boxes". Keep that in mind - you may find better longevity with a newer box. How about a GT transaxle?

 

'85+ syncro ring design patent is Borg Warner but I don't believe any parts are from them.

IIRR there could be one more obstacle in swaping pinion shaft between '85-86 and later boxes. I believe S4, GT or GTS gearbox has larger diameter front end in pinion shaft than earlier boxes. This means input shaft will also have to be changed when pinion changes. Which means also front gear in lay shaft needs to be changed as it's paired with input shaft. I'm sure it's possible to make swap work but it would be much simpler to get other box with shorter final drive. How to find extra '89 GT gearbox without buying entire car is other matter.

 

Given the fact that Porsche outsourced so many individual parts it is probably safe to say that the guts of the transaxles were not built in Zuffenhausen.

 

True but most likely some other company than Borg Warner. Possibly same one which did earlier box internals also. What ever that is.

 

Constantine;

Call me. I have the 60k mile 2.75 LSD box we talked about.

 

Input shaft bearing was changed 92mm vs 100mm when S4 came but did pinion shaft diameter change at same time? IIRR two roller bearings inside input shaft and between GTS input and pinion shafts are different than earlier style. It could have been just to make them stronger and shaft diameter was already changed in '87 MY as you say.

In any case these gearboxes are real minefield if one just desides to swap parts between different types without really looking into it.

 

I have tried to ask Mr. Kibort a few times about what his car has for a trans and never got a reply.

Oh well,
Constantine