Help! I'm working on a LS swap into a 88 GMC OBS
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Teching In
Joined: Mar 2025
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Help! I'm working on a LS swap into a 88 GMC OBS I'm working on putting a 6.2 LS into a 88 GMC OBS. The transmission that I have is a 6L80 that is 4wd. To convert to 2wd you have to take apart the transmission, correct? Any recommendations on what is the best option for a automatic 2wd transmission?
Sure will depending on how you are doing it the 88-89 trucks with white ribbon gauges use VSS input off tranny directly to the cluster and has internal processing to operate speedo and calibrate for tire size and axle ratio. 90-94 uses a DRAC module to drive the speedo and cruise and send mph info to stock TBI ecm. If you leave the stock speedo wiring intact you plug it in to the output shaft speed sensor on the 4L80 and speedo works.
Really best thing to do would be trash can the stock cluster and go with a dakota digital setup it more modern adds a tach and all kinds of nice features. the 88-89 clusters were crappy even when they were brand new.
Depending on who is building your engine harness and how you are doing the tie in to the stock truck You can have harness built and will be using a stock gm TCM to run the 4L80 and there is programming to be done to make sure ecm and tcm cooperate. Nowday's you can buy harness' from sponsors on here to control ecm tcm packages turn key ready to roll. Especially for DIY in garage it's really the only way to roll and for the amount they cost you are time money and frustration ahead.
Really best thing to do would be trash can the stock cluster and go with a dakota digital setup it more modern adds a tach and all kinds of nice features. the 88-89 clusters were crappy even when they were brand new.
Depending on who is building your engine harness and how you are doing the tie in to the stock truck You can have harness built and will be using a stock gm TCM to run the 4L80 and there is programming to be done to make sure ecm and tcm cooperate. Nowday's you can buy harness' from sponsors on here to control ecm tcm packages turn key ready to roll. Especially for DIY in garage it's really the only way to roll and for the amount they cost you are time money and frustration ahead.
Last edited by 01WS6/tamu; Mar 13, 2025 at 09:48 PM.
6L80s good but it's not a direct bolt in especially since you have to take it apart to swap the output shaft. You'll also have to figure out a shifter of some sort the stock column shifter and linkage setup wont work on a 6L80. whereas it will line right up with the 4L80.
Pros and cons to each all depends on what your after and your knowledge level. 4L80 easiest from a drop in a roll and integrate into your existing truck with least fabwork.
Pros and cons to each all depends on what your after and your knowledge level. 4L80 easiest from a drop in a roll and integrate into your existing truck with least fabwork.