L29 4l80E upgrades for towing
Thread Starter
Teching In
Joined: Apr 2017
Posts: 47
Likes: 1
From: Oregon
L29 4l80E upgrades for towing I had a thread here about two years ago on the 4l60e in a 1995 light duty G30 van. The help others provided was great, and the transmission is still going strong. What I found in a towing application with 4.10 gears was the spacing of the ratios on the 4l60e was not the best. Often I had the power for the most part, but I would have a choice of slightly lugging the engine in 3rd or down shifting to 2nd with a much larger increase in rpm than I really needed. I thought about removing the trans for a 4l80e swap, but really it would be a waste since I put so much time and money into the 4l60. I put a high price on the van and put it on Craigslist with a list of the parts I had changed and it sold quickly.
So now I have a two owner, grandpa owned, 1996 c2500 with a 454,4l80e and 4.10s. The trans seems to be in usable shape at 110,000 miles. The fluid is not bad, but not great either so the plan so far is a larger transmission cooler plus service and flush. I know this is a much heavier duty platform to start off with, but is there anything I may change right off the bat to help the transmission out? I tried to research the subject here and it seems there is a lot of modifications you can do during a rebuild, but hopefully that will not be required for a while. I do see the 4L80E-LB1 is suggested in a few places and I think that's doable with just the pan off, if its like the 4l60e. Its not raced, just something to tow 5-6000 pounds of trailer and gear up the mountains here in Oregon.
So now I have a two owner, grandpa owned, 1996 c2500 with a 454,4l80e and 4.10s. The trans seems to be in usable shape at 110,000 miles. The fluid is not bad, but not great either so the plan so far is a larger transmission cooler plus service and flush. I know this is a much heavier duty platform to start off with, but is there anything I may change right off the bat to help the transmission out? I tried to research the subject here and it seems there is a lot of modifications you can do during a rebuild, but hopefully that will not be required for a while. I do see the 4L80E-LB1 is suggested in a few places and I think that's doable with just the pan off, if its like the 4l60e. Its not raced, just something to tow 5-6000 pounds of trailer and gear up the mountains here in Oregon.
TECH Junkie
Joined: Dec 2012
Posts: 3,618
Likes: 1,328
From: Iowa
Modifications to do with the trans in the vehicle...do the HD2 transgo kit...but don't do all of the steps.
Here's what I recommend based on the most recent instructions I can look at
1-no
2-yes
3-sure. Not needed but ok
4-Hell No
5-Hell no
6 on pg 4---yes. 2nd=.078 3rd=.093 4th=.110
Can go larger on 3rd and 4th but that's a good place to start
6 on pg 5---yes. You really should consider blocking both accumulators altogether...Jakes performance offers an accumulator block off plate...try it without blocking them first...blocked may be too firm for you.
7-absolutely
8-**** no. Transgo bolt is total junk
9-no.
10-you can. Dont need to. Feed hole size will help more
A bunch of internal parts come with the kit but they're optional...not necessary.
When drilling the separator plate, make sure no chips get caught between the layers.
Here's what I recommend based on the most recent instructions I can look at
1-no
2-yes
3-sure. Not needed but ok
4-Hell No
5-Hell no
6 on pg 4---yes. 2nd=.078 3rd=.093 4th=.110
Can go larger on 3rd and 4th but that's a good place to start
6 on pg 5---yes. You really should consider blocking both accumulators altogether...Jakes performance offers an accumulator block off plate...try it without blocking them first...blocked may be too firm for you.
7-absolutely
8-**** no. Transgo bolt is total junk
9-no.
10-you can. Dont need to. Feed hole size will help more
A bunch of internal parts come with the kit but they're optional...not necessary.
When drilling the separator plate, make sure no chips get caught between the layers.
Thread Starter
Teching In
Joined: Apr 2017
Posts: 47
Likes: 1
From: Oregon
Thank you very much for the information. On my 4l60e even at just over 100k, the valve body plate was beat up. I ended up buying a transgo plate to replace it. Is it likely to find the same problems in the 4l80? Just trying to get the parts before I tear it apart. What is the advantage of blocking the accumulators vs just going a bit larger on the feed holes? I am not a trans expert so just wondering.
Last edited by doninmedford; Aug 29, 2019 at 01:46 PM.
TECH Junkie
Joined: Dec 2012
Posts: 3,618
Likes: 1,328
From: Iowa
Blocking the accumulators eliminates the possibilities of leaks down the road. Valve body leaks that is.
The transgo HD2 kit will "dual feed" the direct clutch which will greatly increase the life of the direct (3rd gear) clutch. it also includes a new boost valve for increased pressure. Personally, I would spend the $25 extra and get the sonnax O ring boost valve part number 4l80e-lb1. USE THE STOCK PRESSURE REGULATOR SPRING with the sonnax valve.
Also use the sonnax line to lube pressure regulator valve. it will correct cooler flow and keep the converter from dragging.
If you're really feelin' spunky...spend $100 and get the sonnax AFL reamer kit. probably 80% of the valve bodies I see...I ream and install a new valve.
the kit includes 5 valves so then you can ream friends/people in town's valve body for them...at $25 bucks a pop, with the 4 remaining valves your kit will pay for itself.
The transgo HD2 kit will "dual feed" the direct clutch which will greatly increase the life of the direct (3rd gear) clutch. it also includes a new boost valve for increased pressure. Personally, I would spend the $25 extra and get the sonnax O ring boost valve part number 4l80e-lb1. USE THE STOCK PRESSURE REGULATOR SPRING with the sonnax valve.
Also use the sonnax line to lube pressure regulator valve. it will correct cooler flow and keep the converter from dragging.
If you're really feelin' spunky...spend $100 and get the sonnax AFL reamer kit. probably 80% of the valve bodies I see...I ream and install a new valve.
the kit includes 5 valves so then you can ream friends/people in town's valve body for them...at $25 bucks a pop, with the 4 remaining valves your kit will pay for itself.
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Thread Starter
Teching In
Joined: Apr 2017
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From: Oregon
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