89 gt had a T5 with alum drive shaft changing to C4. Did a search and couldn’t find a definitive answer. Do I need a drive shaft spacer? New motor is dart 427 with P.A. bell with 164 tooth flexplate. Spacer between it and the Trans.

 

only one way to find out put eh d/s in and see if its too shot or not :P

 

Ive never had or installed a c4 only standards. Im not sure how far it needs to slide into the trans to be right.

 

I run NO spacer with my C4s and none of my customers run them with there's. One guy that was gone to be a customer went elsewhere when he got his c4 they ran the spacer and shorty rebuilt the trans due to it. I have seen people run them also with no issues but like I said none of my customers run them and I have not had any issues nor have they for years.

 

Great Thanks

 

On fox cars you dont need them but on an sn body you have to use them or you will only have about 1/4in of spline engagement! I believe it is due to the wheel base being a bit longer on the sn cars!

One way around it is an aftermarket k-member that alows you to move the engine backwards into the car. You also have to move your crossmember mounting brackets forward on the sn cars but the fox will bolt directly into the original spot, the AOD and the c4 are almost the same in overall length, the aode is like a c6 in comparison, that is why you have the different wheelbase. I can vouch for every word just done one of each! hasnt been a month ago so its fresh on the mind lol!

 

I have a upr cm k member that has 2 motor mount slots. Are you saying i should use the rear slot and no spacer or the front slot and still no need for spacer? The new motor is going to make over 700 hp so i need to make sure i have enough shaft in the trans.

 

Well you can use the rear slot and move the cg rearward on the car plus make sure you have enough spline engagement....

On the aftermarket k-members that is exactly why the have the 2 mount slots!

All in all itll be a mock up and measure then make a final judgement call on what your results are...

 

That sounds like a good plan. Thanks for your help.