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4th Gen LT1 to LSx swap issues...

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Old 07-13-2015, 08:52 PM
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Default 4th Gen LT1 to LSx swap issues...

I'll point this specifically to you good folks in the conversion group.
My setup before conversion;
  • 96 Z28 LT1
  • Two setups on transmission. Stock T56 and Th350 with 9" tailshaft.
  • stock Ls1 aluminun driveshaft
  • Two setups on engine Crossmember. Stock and BMR tubular
  • Canton Roadrace pan cleared both engine crossmembers.
  • Canton Roadrace pan cleared both engine crossmembers.

Conversion setup;
  • 96 Z28 5.3 engine
  • Th350 with 9" tailshaft.
  • stock Ls1 aluminun driveshaft
  • Engine Crossmember used 4th Gen Fbody UMI tubular.
  • Brand new GM stock engine mounts.


Issues I'm having;
  • stock driveshaft is now too short by at least an inch.
  • Stock LSx Fbody oil pan is resting on top of the Tubular K member.

Did any of you with similar 4th gen swaps find this to be true on your setup?
Thanks,
Dave
Old 07-13-2015, 08:52 PM
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Are the engine mounts symmetrical? Ie: can they be installed upside down?
Old 08-10-2015, 08:05 AM
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Early on in my acquiring of parts, I put out a search for a used Tubular LSx Fbody Kmember. A guy responded and I sent him the money, he sent the KMember. It was awhile till I actually installed it on the motor while it was still on the engine stand. Even then, I didn't notice something I should have. A few months later, I put the assembly of engine and Kmember in my 96 Z28. It was when I put my brand new BMR Torque arm relocator (for Fbody, LS1 to TH350) than I noticed something was amiss. Here's a picture of the torque arm relocator as it comes from BMR




Here's where I had to remove material from the slot to get the transmission mount bolt to go in.




Frustrated but thinking that BMR might have sent the incorrect Crossmember, I went to install my stock LS1 length driveshaft. WTH? That was too short by about an inch also. Mind you, I've ran this same 9" tailshaft TH350 with the LT1 and the driveshaft fit perfectly. And the stock LS1 driveshaft is interchangeable between LS1 Fbodys and LT1 fbodies. Obviously, the engine and transmission are too far forward by about an inch.

This points to the used crossmember. So when I go to inspect it closer to see if it's been rewelded, THAT is when I also notice the Fbody oil pan is sitting right on the Kmembers cross bar. Not a fraction of an inch off of it, ON it.

Two days ago, I asked a fellow Fbud if I could borrow his stock LS1 Fbody cross member so I could swap them out and see where the oil pan, driveshaft and transmount would end up. I won't be able to get to the swap for a couple of weeks (working out of town). This has been so frustrating. My car has been down for almost a year because of various issues way beyond my control.
Old 04-09-2016, 10:54 AM
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Did you ever get this figured out? I'm in the middle of an ltx to lsx swap using the same trans crossmember as you and ran into the SAME issue. Trans is about 1" too far forward. I'm using a factory ls1 k member and mounts...
Old 04-09-2016, 11:31 AM
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Exactly the same as you. Whether I used the tubular or stock K member, it was same thing. I was expecting to be able to use my stock drive shaft and that bolt on trans X member. Sooo frustrating. Did you end up slotting the trans bolt hole like I did? I'm going to pull it back off and weld an extension on it I guess.



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