Harsh Trans Engagements 4L80E
Harsh Trans Engagements 4L80E 2008 4X4, lifted 6", 35" tires, went from a 4L60E to a 4L80E
I'm experiencing harsh engagements after the swap. When the engine is started, and the trans is shifted into "R", the truck bangs in pretty hard. This is exacerbated by the fact that the truck is 4X4 so there is extra "slop" coming out of the t-case. It also has a firmer-than-I'd-like "F" (forward) engagement.
Is there a line pressure adjustment that can be made using HP Tuners that would allow a lower line pressure (static line pressure) to aid in reducing the harshness of the engagements? I was able to segment swap this vehicle to get the correct OS installed, and get it up, running, and shifting. It's just the engagements are startling. The trans has a NEW EPC in it already. No codes being stored. It has over 500 miles on it since the swap and the engagements are the only problem at this point. All upshifts are firm, but livable. I have experienced this previously on vehicles that have high numeric gear ratios installed in the axles. This particular truck has 35" tall tires, and 4:56 gears in the differentials.
Any advise would be greatly appreciated. I posted here because it is potentially a "tuning" issue.
I'm experiencing harsh engagements after the swap. When the engine is started, and the trans is shifted into "R", the truck bangs in pretty hard. This is exacerbated by the fact that the truck is 4X4 so there is extra "slop" coming out of the t-case. It also has a firmer-than-I'd-like "F" (forward) engagement.
Is there a line pressure adjustment that can be made using HP Tuners that would allow a lower line pressure (static line pressure) to aid in reducing the harshness of the engagements? I was able to segment swap this vehicle to get the correct OS installed, and get it up, running, and shifting. It's just the engagements are startling. The trans has a NEW EPC in it already. No codes being stored. It has over 500 miles on it since the swap and the engagements are the only problem at this point. All upshifts are firm, but livable. I have experienced this previously on vehicles that have high numeric gear ratios installed in the axles. This particular truck has 35" tall tires, and 4:56 gears in the differentials.
Any advise would be greatly appreciated. I posted here because it is potentially a "tuning" issue.
Tdoug-I have not put a gauge on it yet. I suppose I could do that next. However, it still begs the question-is this something that can be "tuned" or otherwise adjusted in HP Tuners? I do have other options; Manually turn the line pressure down by using the screw on the back of the EPC. Then the problem becomes, how will i insure that I'm running enough line pressure once rolling down the road? I don't want to reduce line pressure anywhere other than when in PARK, or NEUTRAL.
I forgot to mention that the truck has been tuned previously for a cam swap. Whoever did the swap has it tuned such that it flares pretty badly on initial start up-like up to 1300 RPM, and it has a fairly high idle for such a very mild cam.. It idles currently at 850. I mention this because I could set it to idle significantly lower in the P or N fields, and then raise the idle for the IN GEAR ranges (if it even needs it). It's a very mild cam, and they have it tuned as if it's got 230-240 degrees of duration. Probably a "canned" tune. I have not dug around in the engine settings side yet. I'm sure I could reduce engine idle speed, remove the extra air on start up to cure the flare, and then see where it's at from there. However, I think something is going to have to be done about the engagements even after that.
I forgot to mention that the truck has been tuned previously for a cam swap. Whoever did the swap has it tuned such that it flares pretty badly on initial start up-like up to 1300 RPM, and it has a fairly high idle for such a very mild cam.. It idles currently at 850. I mention this because I could set it to idle significantly lower in the P or N fields, and then raise the idle for the IN GEAR ranges (if it even needs it). It's a very mild cam, and they have it tuned as if it's got 230-240 degrees of duration. Probably a "canned" tune. I have not dug around in the engine settings side yet. I'm sure I could reduce engine idle speed, remove the extra air on start up to cure the flare, and then see where it's at from there. However, I think something is going to have to be done about the engagements even after that.
yes there's a per gear shift pressure vs tps % table in HPT
it doesnt have a whole ton of range though. I have a trans right now that had a slushy 1-2 that turned out to be the valve bore being worn a bit. I added a "shift saver" spring and even with the pressure vs tps zeroed on the 1-2 it'll still snap your neck if you arent ready for it. its coming out soon for a proper fix.
usually a big stall will eat much of a harsh shift if you have modded for high line pressures, but I have taken to adding wave plates in the fwd, direct and intermediate clutches so I can max line pressure for holding power and not knock my teeth out street driving.
it doesnt have a whole ton of range though. I have a trans right now that had a slushy 1-2 that turned out to be the valve bore being worn a bit. I added a "shift saver" spring and even with the pressure vs tps zeroed on the 1-2 it'll still snap your neck if you arent ready for it. its coming out soon for a proper fix.
usually a big stall will eat much of a harsh shift if you have modded for high line pressures, but I have taken to adding wave plates in the fwd, direct and intermediate clutches so I can max line pressure for holding power and not knock my teeth out street driving.
That's probably the biggest issue here... No cushion plates in the direct drum (which affects reverse engagement), and no cushion plate in the forward drum (which affects Forward engagement). Deletion of the cushion plates is what allows the addition of 7 frictions, and 7 Kolene steels in both the forward and direct drum. So, with the ability to handle big loads of horsepower & torque, turbos, and/or nitrous, the trade off is U-joint snapping engagements due to the much increased surface area due to the extra frictions, and the deleted cushion plates. For reverse, I could always increase the size of the return spring for the reverse band servo. Alternately, I could research reducing the feed hole for reverse in the separator plate. That could effectively slow the engagement of the band and potentially soften the "hit". Or, I could pull the trans out, and put the cushion plates back in.. If I can't "tune" it out, then that is a last resort. It does not help that this trans has had the internal dual fed direct mod performed.
Last edited by Kawabuggy; Feb 18, 2020 at 04:26 PM.
I have tuned alot of 4l80 swaps in those trucks and in camaros and they all shift normal even 1,000+hp turbo setups. Never had to do anything in the tune to make one not bang into gear. Have you tried stock 4l80 line pressure settings? A bone stock 08 truck will rev to 1200 rpm on a 100% cold start, most people just never notice it until they get a tune and then ask why it rev's so high on startup. 850 rpm could be a little high for normal idle.
yeah i delete that skinny wave for a .060 wave, less shock loading as the piston applied...without burning anything
i aim for 5 in the fwd and 6 in the direct with a cut down th400 piston....around .040 end clearance on both.
especially with the dual feed mod you need to keep an eye on pressures
i aim for 5 in the fwd and 6 in the direct with a cut down th400 piston....around .040 end clearance on both.
especially with the dual feed mod you need to keep an eye on pressures
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