99 Suburban Transmision Swap - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1bcooper · 05-21-2009, 10:31 AM

99 Chv C1500, 4L60E transmission with cooler/towing, etc. I have blown three transmisisons.
*Can you replace the 4L60E with the heavier 4L80E?
Will the computer still work?

I am towing a 6000# Airstream.

**bwood** · 05-21-2009, 09:48 PM

I believe the 4L80E is longer and will require the crossmember to be moved back and a custom driveshaft. Also the ECM will need to be reprogrammed for the 4L80E as the internal gear ratios are different and it wouldn't shift correctly. What has killed you other transmissions? I wouldn't think a 6k# camper would do it. I know a few guys pulling more and have had no issues. What is your gear ratio? If it is kinda low (numerically low), like 3.42 or 3.23, you may concider a gear swap to something like 3.73. This will negatively affect your mileage when you are not pulling, but will take some strain off the trans. Are you using your tow haul buton at the end of the shifter? How fast do you drive while pulling?

BTW, welcome to the board.

1bcooper · 05-29-2009, 08:37 AM

I have a 3:42 rear end. I tow 60mph.

jgreene0717 · 05-29-2009, 12:53 PM

Do you pull it in overdrive or do you put the transmission in 3rd gear. If it where me I would not pull at 60 mph in overdrive.

1bcooper · 05-29-2009, 04:03 PM

I do both. If I am on a real flat interstate, etc. I will keep it in Drive. Most of the time, however, I am pulling in 3.

**bwood** · 05-29-2009, 11:22 PM

How many miles on the trans? Before I went to the trouble to convert over to the 80E, I would look into beefed up 60E made for towing. This way its a direct bolt in. I also have 3:42 in my truck and it is pain to pull much more than my bike trailer. My friend has the same truck as mine with the V6/auto with 4.10s (I think) and it will pull better than mine. Of course mileage isn't as good. We used his truck and my trailer while I was putting a new engine in mine. It does sit higher in the RPMs, but it gets down the road without excessive shifting with it in 3rd/OD. He pulls like you do, OD on flat ground and 3rd everywhere else.

**Captainfab** · 05-29-2009, 11:33 PM

Quote:

Originally Posted by 1bcooper

99 Chv C1500, 4L60E transmission with cooler/towing, etc. I have blown three transmisisons.
*Can you replace the 4L60E with the heavier 4L80E?
Will the computer still work?

I am towing a 6000# Airstream.

The wiring harness for the 4L80E is different than the 4L60E harness. Plus as was already posted the PCM will need to be reflashed.

05-21-2009, 10:31 AM	#1
1bcooper Registered User Join Date: Apr 2009 Location: Pauline, SC Posts: 5	99 Suburban Transmision Swap 99 Chv C1500, 4L60E transmission with cooler/towing, etc. I have blown three transmisisons. *Can you replace the 4L60E with the heavier 4L80E? Will the computer still work? I am towing a 6000# Airstream.

05-21-2009, 09:48 PM	#2
bwood Registered User Join Date: Jan 2003 Location: Denison, Texas Posts: 1,919	Re: 99 Suburban Transmision Swap I believe the 4L80E is longer and will require the crossmember to be moved back and a custom driveshaft. Also the ECM will need to be reprogrammed for the 4L80E as the internal gear ratios are different and it wouldn't shift correctly. What has killed you other transmissions? I wouldn't think a 6k# camper would do it. I know a few guys pulling more and have had no issues. What is your gear ratio? If it is kinda low (numerically low), like 3.42 or 3.23, you may concider a gear swap to something like 3.73. This will negatively affect your mileage when you are not pulling, but will take some strain off the trans. Are you using your tow haul buton at the end of the shifter? How fast do you drive while pulling? BTW, welcome to the board. __________________ 1998 GMC Sierra SLE 1/2 ton 2WD 305 Vortec -Gibson Stainless Cat Back Swept Side -SS Wheels 2005 Honda CRF250R 2006 Honda CRF150F Last edited by bwood; 05-21-2009 at 09:48 PM.

05-29-2009, 08:37 AM	#3
1bcooper Registered User Join Date: Apr 2009 Location: Pauline, SC Posts: 5	Re: 99 Suburban Transmision Swap I have a 3:42 rear end. I tow 60mph.

05-29-2009, 12:53 PM	#4
jgreene0717 Jason Join Date: Sep 2008 Location: Wetumpka, AL Posts: 152	Re: 99 Suburban Transmision Swap Do you pull it in overdrive or do you put the transmission in 3rd gear. If it where me I would not pull at 60 mph in overdrive.

05-29-2009, 04:03 PM	#5
1bcooper Registered User Join Date: Apr 2009 Location: Pauline, SC Posts: 5	Re: 99 Suburban Transmision Swap I do both. If I am on a real flat interstate, etc. I will keep it in Drive. Most of the time, however, I am pulling in 3.

05-29-2009, 11:22 PM	#6
bwood Registered User Join Date: Jan 2003 Location: Denison, Texas Posts: 1,919	Re: 99 Suburban Transmision Swap How many miles on the trans? Before I went to the trouble to convert over to the 80E, I would look into beefed up 60E made for towing. This way its a direct bolt in. I also have 3:42 in my truck and it is pain to pull much more than my bike trailer. My friend has the same truck as mine with the V6/auto with 4.10s (I think) and it will pull better than mine. Of course mileage isn't as good. We used his truck and my trailer while I was putting a new engine in mine. It does sit higher in the RPMs, but it gets down the road without excessive shifting with it in 3rd/OD. He pulls like you do, OD on flat ground and 3rd everywhere else. __________________ 1998 GMC Sierra SLE 1/2 ton 2WD 305 Vortec -Gibson Stainless Cat Back Swept Side -SS Wheels 2005 Honda CRF250R 2006 Honda CRF150F



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