Hi Everyone-
I've got a 3rd gen Firebird, and I just got a 98 C5 LS1 to put in it.
I got a T-56 for the car in 99. It does not have a lot of miles on it, and is set up for my mechanical speedo. I would like to keep it.
So, I understand it is a modified LT tranny, what do I need to do?
Thanks, especially to those in foul weather situations.

 

You need to change the front (mid) plate of the case, that supports the hyd slave, and replace the LT1 input shaft to the longer one from an LS1.

Since the tail is (basically) the same between the 2, it might be easier to just swap your tail over to an LS1 trans. Depends on how the speedo driven gear is installed on your existing LT1 trans... You might be able to get most of your $$ back by reselling the LT1 trans with the swapped elect VSS setup.

 

Thanks, Mike

 

I just finished my T56 install in my 3rd gen Camaro yesterday. I used an LT1 style trans. With an Lt1 style trans you can use your existing drive shaft, with the LS you will have to shorten yours. But if you go with the LT style, you will have to get the bell housing and clutch setup for an LT1, and the mid plate and the shorter LT style input as 85MikeTPI mentioned. It's almost a bolt in to go with an LT style trans. With the LS1 style it uses a standard push style clutch setup, but spaces the trans back necessitating the drive shaft shortening and shifter relocation.

My car was a manual setup, so all I had to do was swap in the 4th gen hydraulics. The third gen clutch line isn't long enough for the slave to be mounted pointing forward on the LT setup. I'd read that you can just use the longer braided 4th gen clutch line with the 3rd gen hydraulics, but the fittings were different than the ones on my 87 so I used the complete 4th gen setup.

The master cylinder push rod also needed a little modding to make it fit. The bushing in the end of the rod wasn't big enough to go over the stud on my clutch pedal, but if you pop that bushing out you can put he 3rd gen bushing in. Exact same size hole. You will need to narrow the clevis end somewhat. As I recall about .050. I didn't want to bother breaking down the setup my milling machine to do this, so I just used my belt sander and went slow. Worked perfectly.

You will also need a T56 cross member. Be sure and specify if your using an LS or LT style trans when you order. They are available from several sources. Spohn, Skulte, ect. I had to cut back the floor pan about 1 inch to clear the T56 shifter setup. With an LS style trans you will have to cut much further, and move the shifter forward and to the left. With my Lt trans I just moved the shifter to the left with a 1-1/4" spacer block I made. I used a Hurst comp plus shifter and all I had to do was get longer bolts in able to use the spacer block.

It's good you have a tail housing that's set up for a speedo cable drive. I own a machine shop and worked this out on my own and now I do this mod for others. Works perfectly, speedo is steady and does not bounce.

This was a lot of work, but in the end it was worth it. I rebuilt my trans with all the good parts and I'm glad I did. To say this thing shifts like butter is an understatement. Other than being sore all over today, I couldn't be happier with the outcome of this swap.

If you have any questions, please feel free to ask. It's all still fresh in my mind.

 

Alloy-
Thanks for the long post. I have the T-56 in. I am changing from a 383, to an LS1 (from a 'vette).
I also have an early 3rd Gen, so my current clutch is mechanical!! Guess I should look for the 4th Gen pedals. I knew that, but you underlined it.

 

You really don't need 4th gen pedals, third gen will work perfectly and easier to find. You just need the 4th gen hydraulics with the longer clutch hose if your going with an LT1 style setup.

 

The attachment point on the clutch pedal may be different on third gen pedals you find vs. the fourth gen pedals you find. If you can find 84-92 pedals, those are fine. Or you could add a smooth o.d. stud to your clutch pedal for the master cylinder. Good luck on your swap.

 

Thanks, guys.