85 Suburban TH400 to 4L80E swap - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GRADYS Performance · 12-18-2013, 02:56 PM

I am preparing to change the TH400 in my 85 2WD C20 Suburban 454 to a 4L80E transmission. Does anyone have experience with what needs to be done for the crossmember?

68Timber · 12-18-2013, 06:47 PM

How to here: http://67-72chevytrucks.com/vboard/s...d.php?t=574800

GRADYS Performance · 12-19-2013, 11:27 AM

No details in that thread about the cross member modifications.

68Timber · 12-19-2013, 11:43 AM

I think he said he used the stock cross member with the 4L80E mount.

CamaroChris · 12-20-2013, 12:39 AM

when I put an 6.0l/4l80e in my 86 Suburban (originally a 350/th400) I used Dirty Dingo mounts. all I had to do was re-drill the cross member holes in the frame around 1.5" back. but the cross member its self needed no modification. The 4l80e trans bushing bolted right to the cross member.

GRADYS Performance · 01-14-2014, 05:17 PM

I am starting this swap project. I have the transmission and torque converter complete and ready to install. Transmission is fresh overhauled with a shift kit, manual speedometer output housing with gears and deep aluminum pan.

I will try to update with progress and pictures as I work on it and make progress.

GRADYS Performance · 05-10-2014, 03:06 PM

Moved the transmission crossmember back to line up the front crossmember bolt holes with the rear bolt holes in the frame and the mount on the transmission lines up perfectly. Drilled new rear holes in the frame using the crossmember as a template and bolted everything up. Transmission and torque converter are now installed and bolted in.

GRADYS Performance · 07-14-2014, 10:50 AM

Driveshaft shortened 3-3/8 inches and re installed. Cooler lines from TH400 moved back 2-3 inches and re bent to fit 91-96 4L80E case.

GRADYS Performance · 07-26-2014, 09:26 AM

Installing the TCI Transmission control unit and TPS sensor this weekend, That just leaves the shifter linkage and speedometer cable left to finish up.

Hankster · 03-11-2015, 07:47 PM

Nice write up, I have been thinking about the swap with my 454 swapped c10 if you could please send me that info also! Thank you!

GRADYS Performance · 03-11-2015, 08:18 PM

Quote:

Originally Posted by Hankster

Nice write up, I have been thinking about the swap with my 454 swapped c10 if you could please send me that info also! Thank you!

I sent a PM to you about the speedometer conversion.

72MARIO · 03-12-2015, 12:28 PM

Any reason not to post the speedo conversion info here ? I am interested too. Do you sell the kit ?

GRADYS Performance · 03-12-2015, 03:16 PM

Quote:

Originally Posted by 72MARIO

Any reason not to post the speedo conversion info here ? I am interested too. Do you sell the kit ?

I sent a PM to you about the Speedometer conversion kit that we offer.

zipper421 · 09-28-2018, 08:49 AM

could you send me the speedo info to

GRADYS Performance · 09-28-2018, 09:36 AM

I will send the Info to you.

BigDooley77 · 10-17-2018, 08:27 PM

Grady's Performance did you use the th400 linkage part that's on the trans or did you use a 4l80e? I'm almost done with my swap and am stuck on this

BigDooley77 · 10-18-2018, 03:58 PM

nevermind figured it out

http://67-72chevytrucks.com/vboard/s....php?p=6834660

12-18-2013, 02:56 PM	#1
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 366	85 Suburban TH400 to 4L80E swap I am preparing to change the TH400 in my 85 2WD C20 Suburban 454 to a 4L80E transmission. Does anyone have experience with what needs to be done for the crossmember?

12-18-2013, 06:47 PM	#2
68Timber I know the pieces fit Join Date: Nov 2007 Location: MONTGOMERY, AL Posts: 5,523	Re: 85 Suburban TH400 to 4L80E swap How to here: http://67-72chevytrucks.com/vboard/s...d.php?t=574800 __________________ John 79 2wd Blazer (Bruiser) 85 M1009 Blazer (Sarge) build 74 Honda Z50 build

12-19-2013, 11:27 AM	#3
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 366	Re: 85 Suburban TH400 to 4L80E swap No details in that thread about the cross member modifications.

12-19-2013, 11:43 AM	#4
68Timber I know the pieces fit Join Date: Nov 2007 Location: MONTGOMERY, AL Posts: 5,523	Re: 85 Suburban TH400 to 4L80E swap I think he said he used the stock cross member with the 4L80E mount. __________________ John 79 2wd Blazer (Bruiser) 85 M1009 Blazer (Sarge) build 74 Honda Z50 build

12-20-2013, 12:39 AM	#5
CamaroChris Registered User Join Date: Mar 2011 Location: Midvale, Utah Posts: 220	Re: 85 Suburban TH400 to 4L80E swap when I put an 6.0l/4l80e in my 86 Suburban (originally a 350/th400) I used Dirty Dingo mounts. all I had to do was re-drill the cross member holes in the frame around 1.5" back. but the cross member its self needed no modification. The 4l80e trans bushing bolted right to the cross member. __________________ I LIKE TRUCKS 1986 GMC Suburban Build Build link 1982 Chevy SWB 2wd Scottsdale, Build Link Sold 1987 Jimmy Build, Project Cheap A$$ Build Link

01-14-2014, 05:17 PM	#6
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 366	Re: 85 Suburban TH400 to 4L80E swap I am starting this swap project. I have the transmission and torque converter complete and ready to install. Transmission is fresh overhauled with a shift kit, manual speedometer output housing with gears and deep aluminum pan. I will try to update with progress and pictures as I work on it and make progress.

05-10-2014, 03:06 PM	#7
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 366	Re: 85 Suburban TH400 to 4L80E swap Moved the transmission crossmember back to line up the front crossmember bolt holes with the rear bolt holes in the frame and the mount on the transmission lines up perfectly. Drilled new rear holes in the frame using the crossmember as a template and bolted everything up. Transmission and torque converter are now installed and bolted in.

07-14-2014, 10:50 AM	#8
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 366	Re: 85 Suburban TH400 to 4L80E swap Driveshaft shortened 3-3/8 inches and re installed. Cooler lines from TH400 moved back 2-3 inches and re bent to fit 91-96 4L80E case.

07-26-2014, 09:26 AM	#9
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 366	Re: 85 Suburban TH400 to 4L80E swap Installing the TCI Transmission control unit and TPS sensor this weekend, That just leaves the shifter linkage and speedometer cable left to finish up.

03-11-2015, 07:47 PM	#10
Hankster Registered User Join Date: Jan 2013 Location: Nacogdoches, Texas Posts: 895	Re: 85 Suburban TH400 to 4L80E swap Nice write up, I have been thinking about the swap with my 454 swapped c10 if you could please send me that info also! Thank you! __________________ Current Build 89 s10 ecsb 2wd 4.3/700r4 50k OG Miles Instagram- shaggin_s10 '86 Chevrolet C10 Custom Deluxe - Gen V 454 - 4l80e - welded 12 bolt (Build thread: http://67-72chevytrucks.com/vboard/s...d.php?t=611611 ) SOLD

03-12-2015, 12:28 PM	#12
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,052	Re: 85 Suburban TH400 to 4L80E swap Any reason not to post the speedo conversion info here ? I am interested too. Do you sell the kit ? __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD

09-28-2018, 08:49 AM	#14
zipper421 Registered User Join Date: Sep 2018 Location: syracuse ny Posts: 1	Re: 85 Suburban TH400 to 4L80E swap could you send me the speedo info to

09-28-2018, 09:36 AM	#15
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 366	Re: 85 Suburban TH400 to 4L80E swap I will send the Info to you.

10-17-2018, 08:27 PM	#16
BigDooley77 Registered User Join Date: Sep 2016 Location: No Where,KS Posts: 57	Re: 85 Suburban TH400 to 4L80E swap Grady's Performance did you use the th400 linkage part that's on the trans or did you use a 4l80e? I'm almost done with my swap and am stuck on this __________________ 1977 GMC Sierra Classic CCDW. 454 worked 781s, 277/287, Lift .502/.501 LS 114, Dual plane intake, Dana 70 (4.10) and 4L80e (HD2 kit). http://67-72chevytrucks.com/vboard/s...63#post8361863

10-18-2018, 03:58 PM	#17
BigDooley77 Registered User Join Date: Sep 2016 Location: No Where,KS Posts: 57	Re: 85 Suburban TH400 to 4L80E swap nevermind figured it out http://67-72chevytrucks.com/vboard/s....php?p=6834660 __________________ 1977 GMC Sierra Classic CCDW. 454 worked 781s, 277/287, Lift .502/.501 LS 114, Dual plane intake, Dana 70 (4.10) and 4L80e (HD2 kit). http://67-72chevytrucks.com/vboard/s...63#post8361863



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