1979 C30 Transmission Swap - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Yamaharyder600 · 07-22-2015, 10:30 PM

Hello,
I have a 1979 C30 with a 350, th400, and 4.56 rear end gearing. Looking to swap to a 4spd auto to pickup the over drive. Right now I really cant do any highway driving due to lack of top end. The two options I am considering are the 4L80e and the 4L85e. I have access to either. My biggest question is do these two transmissions as similar as they are to each other share the same valve body? Looking to use a manual valve body and eliminate the electronic aspect. I have found the manual bodys listed for the 4l80 but not the 4l85. Can anyone clear this up?

bilfman · 07-23-2015, 12:16 AM

Put in a 4l80e with a TCI controller , it is a very simple swap, I did one and was apprehensive about the electronic side the TCI kit makes it simple. I posted a build thread on here.

bns454 · 07-30-2015, 08:36 AM

I have a 4l80 (cable) behind the 454 in my cc dually it dropped the rpm to 2200 at 75mph (was 3300 at 70mph with t400) im happy with the trans as I don't tow or have it loaded its just used as a everyday driver.
im pretty sure the 4l80e has a bigger hole in the case for the wiring plug and no cable hole so don't think the valvebody will interchange

07-22-2015, 10:30 PM	#1
Yamaharyder600 Registered User Join Date: Jun 2015 Location: Tarentum, PA Posts: 1	1979 C30 Transmission Swap Hello, I have a 1979 C30 with a 350, th400, and 4.56 rear end gearing. Looking to swap to a 4spd auto to pickup the over drive. Right now I really cant do any highway driving due to lack of top end. The two options I am considering are the 4L80e and the 4L85e. I have access to either. My biggest question is do these two transmissions as similar as they are to each other share the same valve body? Looking to use a manual valve body and eliminate the electronic aspect. I have found the manual bodys listed for the 4l80 but not the 4l85. Can anyone clear this up?

07-23-2015, 12:16 AM	#2
bilfman Registered User Join Date: Dec 2011 Location: Regina, SK, Canada Posts: 622	Re: 1979 C30 Transmission Swap Put in a 4l80e with a TCI controller , it is a very simple swap, I did one and was apprehensive about the electronic side the TCI kit makes it simple. I posted a build thread on here. __________________ 1979 Chevy Dually Crew 4X4 454, D60 Tru-trac, D70 Detroit Locker, 3.73, 4L80E/NP205 1971 GMC 3/4 Ton 4X4

07-30-2015, 08:36 AM	#3
bns454 Registered User Join Date: Jan 2013 Location: sydney australia Posts: 56	Re: 1979 C30 Transmission Swap I have a 4l80 (cable) behind the 454 in my cc dually it dropped the rpm to 2200 at 75mph (was 3300 at 70mph with t400) im happy with the trans as I don't tow or have it loaded its just used as a everyday driver. im pretty sure the 4l80e has a bigger hole in the case for the wiring plug and no cable hole so don't think the valvebody will interchange



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