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GRADYS Performance · 09-08-2014, 11:06 AM

You will have to use a 4L80E that has an output shaft that takes a bolt on yoke. The slip yoke transmission will not work with a 2 piece drive shaft. The Bolt on yoke transmission will have a threaded bolt hole in the end of the output shaft just like your original TH400. You can change the output shaft in the 4L80E but the transmission will have to be taken apart to do it. The shifter linkage will have to be moved on the frame and the shifter rod from the steering column will have to be lengthened about 2". Here is a picture of the frame mount from my 4L80E conversion. Move the bracket back putting the front bracket hole in the rear frame hole. I spaced mine down about 1/4" at the same time. Could not move it down more because of exhaust clearance.

09-08-2014, 11:06 AM	#5
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 366	Re: Retrofitting 4l80e, couple questions. You will have to use a 4L80E that has an output shaft that takes a bolt on yoke. The slip yoke transmission will not work with a 2 piece drive shaft. The Bolt on yoke transmission will have a threaded bolt hole in the end of the output shaft just like your original TH400. You can change the output shaft in the 4L80E but the transmission will have to be taken apart to do it. The shifter linkage will have to be moved on the frame and the shifter rod from the steering column will have to be lengthened about 2". Here is a picture of the frame mount from my 4L80E conversion. Move the bracket back putting the front bracket hole in the rear frame hole. I spaced mine down about 1/4" at the same time. Could not move it down more because of exhaust clearance. Attached Images Last edited by GRADYS Performance; 09-08-2014 at 11:17 AM.