C. Tips for Installing an LT1 or LS1 T56
While I ultimately used a Viper T56, I initially started my T56 swap with a 1997 Camaro LT1 T56, which taught me a few things that you might find useful.
For reference, here we have a LS1 bell (left), McLeod Modular bellhousing (8710-00) and an LT1 bell (right). You’ll notice they have the same depth and very similar mounting holes on both sides.
The LS1 and LT1 bell can mate a chevy engine directly. A common BOP-Chevy adapter can be used to bolt one of these to your Pontiac (
http://www.summitracing.com/parts/TRD-0061/?image=large) to mate the T56 to a Pontiac engine. This is the route I initially though I’d take, with the LS1 bell and adapter. After realizing the LS1 bell is worth $200+ (sold it for $220), and add $100 for the adapter, plus $50 for the custom 0.500” thicker pilot bushing, the bomb proof McLeod Modular bell with a block plate at $425 made a ton more sense on many levels (direct from McLeod I actually got the bell at $325).
A stock LT1 T56 is the least ideal T56 for a Pontiac, as the input shaft is far too short. As you can see here the input shaft doesn’t get anywhere near the pilot hole, which, conveniently for reference, happens to be about dead center of where the block plate aligns.
LT1 input shaft coming up short:
Whereas the LS1 shaft input shaft is about perfect in length:
Here I’ve also illustrated the length difference by placing the shorter LT1 and longer LS1 shaft next to each other:
A LT1 T56 can however easily be modified with a longer LS1 or Viper input shaft, which can be swapped alone or along with the front plate for the LS1 or Viper T56. Here we have the LT1 T56 with the front plate removed. Removing the front plate and input is a simple process. Just remove the bolts on the front plate, pop the plate off and gently pull the shaft out while twisting (sounds dirty, I know ☺ ).
Here I have the LT1 and LS1 front plate and input shafts next to each other so you can clearly see the difference in input shaft height, and the difference in the plate to help easily ID the different versions. The LT1 is designed to have a traditional mechanical throwout bearing (TOB) and fork installed on the plate (not shown), and thus sports a bearing retainer. The LS1 front plate has a machined surface to accept a hydraulic throwout, or more precisely a concentric slave cylinder (CSC).
Installing a new shaft and/or front plate on a T56, is not as easy as removing the original, as you must set the shaft/plate spacing with small spacer shims, as described in the T56 manual linked to here:
http://www.ttcautomotive.com/English...ice_Manual.pdf
Here you see the bearing race removed from the front plate with a thin shim that goes underneath to properly space the input shaft:
While I had the LS1 front plate and input off I did some mock ups to see how it all would fit with the clutch and bell installed in the car. While the spacing for the shaft and pilot is good, unfortunately the factory LS1 CSC is too big to fit in the small bellhousing space without binding, effectively leaving the clutch partially engaged at all times, as shown:
Not a good thing. RAM offers a universal CSC that might work (
http://www.summitracing.com/parts/RA...5/?image=large), though the thought of a hard to find and expensive CSC is not appealing. A McLeod scalloped (8703-13) spacer would be needed to make room for the F-body CSC, or you’d need to find a different TOB setup, perhaps even going with a mechanical TOB setup by using a plate such as this (
http://www.summitracing.com/parts/MC...7/?image=large)
Problem here with the mechanical TOB plate adapter, or the McLeod spacer, is by putting the trans 0.500-0.700” back to fit the TOB, your input shaft is now too short to fully engage the Pilot bearing/bushing, and a custom made bushing is required (and/or use of the longer Viper input shaft). McLeod lists in their catalog a custom extended pilot bushing for Pontiacs just for this very situation, part number 8-1380-1. However, this part is completely wrong, and neither the bushing ID or OD is correct for a Pontiac/Olds crank or any T56 input, respectively. You’d need to have a bushing custom made to make this setup work, which is not a big deal for your local machinist, or perhaps call McLeod to get the proper part number, as they claim in their catalog to make such a bushing.
Thus, the LS1 T56 is a completely workable solution, with just a few different twists to address. At this point I switched gears to make the Viper T56 work in my Poncho, so have nothing more to share here, although the basic install from here on would largely mirror the steps listed for the Viper trans...