Hydraulic throwout on an LT1 T56?

There are a couple threads currently running on the RX-7 forum on adapter plates for rotary engines to allow running GM transmissions, and specifically, the T56 for an extra gear and strength.

In double checking some information I found, I stumbled onto the web page below, which details the installation of a '97 T56 with a hydraulic throwout bearing installed. The "adapter" is a Weir Hotrod Products bellhousing which looks a lot beefier than the stock LT1 bellhousing. It states that the hydraulic assembly bolts to the same mounting point as the stock clutch fork.

http://carbuff.homeip.net/weir.html

So my question is... anyone think this is worthwhile to pursue further? Is a hydraulic throwout bearing better/smoother/faster than the clutch fork/slave cylinder of the LT1 T56? I mean, there has to be a reason why GM switched to using a hydraulic throwout in '98, right? :)

And while I've got your attention, I heard a rumor (stated as fact) that the T56 would not handle "high" rpm. In this case, we're talking about 8,000 rpm. The same person also stated that the LS1 T56 would handle more power than the LT1 version, but I don't believe that to be the case. Tremec rates them both at 450 lb-ft. of torque, I believe. Anyone know differently?

Thanks!

Looks like the LS1 style slave cyl.. Only thing I don't understand is that the LT1 style clutches are pull type, while LS1 are push type. I don't see how "pushing" hyd. fluid via the clutch pedal is going to "pull" on the PP, unless you have to upgrade the clutch (or at least the PP) as well.

Hopefully someone can explain how this works alittle more.

Dave

Originally posted by Prince
Looks like the LS1 style slave cyl.. Only thing I don't understand is that the LT1 style clutches are pull type, while LS1 are push type. I don't see how "pushing" hyd. fluid via the clutch pedal is going to "pull" on the PP, unless you have to upgrade the clutch (or at least the PP) as well.


If you go to a hydraulic throwout bearing, you need to ditch the LT1-style "pull" pressure plate and go with a normal "push" pressure plate (such as that used by the LS1 and nearly every other non-LT1 drivetrain out there).

Most clutch manufacturers should be able to set someone up with this - Doug Wood (fellow T56 Impala owner) had a header interference problem on his car, so he switched to a hydraulic throwout bearing and a standard ("push") pressure plate. It seems to work pretty well for him, once he got the bugs worked out (it seems that he had some problems with the McLeod clutch, like an out-of-balance pressure plate). For more info, go check out the Drivetrain forum on www.impalassforum.com and search for posts by Doug - he's always informative and never boring ;)

Thanks Eric!

As far as strength difference between the years, I don't know for sure, but I would doubt it. There may be a few things different, but nothing drastic. When I cordered a Sean Hyland Ford T56, they had 2 different TQ ratings. One was for 450, and the other 600. When I asked the difference and they told me the ONLY thing was that they go through the 600 one and basically blueprint all the tolerances. Guess the TQ rating is kinda liberal.

Hmmm, I think I remember hearing just the opposite of that statemtent about the LS1 style T56's being stronger. I always thought that the early style models (94-97's) were the stronger ones because they were still being made by Borg Warner here in the U.S. Once Tremec bought the rights to the T56, they were being assembled in Mexico and had a bunch of quality control issues. That was a couple years ago though, so maybe that has changed :think: !

Mike