10 psi when warm

You can't really tip toe around this. Its time to go thru that engine, cam bearings are notorious for failing at that mileage. Save yourself time and energy and just get a crate engine. My old H2 had the same issues and I picked up a new GM 376/495HP which made it fun to drive. Crate stock 6.0's can be had for about $3000 or less. Or get a 6.2 and transmission pull out from a junk yard.

Low mileage, used 6.0s are pretty reasonably priced as well, and most come with some sort of guarantee.

S33k3r said:

Low mileage, used 6.0s are pretty reasonably priced as well, and most come with some sort of guarantee.

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Not likely to find a low mileage Gen 3 6.0L and the problem with going to Gen 4 is that some PCM wiring changes will need to be done and an electronic adapter for the reluctor on the crank will have to be added or replace the Gen4 crank reluctor with a Gen 3 tooth count which would require the crank to be removed.

In Texas I would guess they are out there, at 1 - 2x per day. $1200 was the lowest price I saw.

SnowDrifter said:

Not a good one. But it's accessible by taking off the oil filter. It's a circular press fit doohickie

Of note: that's only for our 'older' engines without cylinder deactivation. The newer ones (07+) have a different system that bleeds oil back into the sump during 4 cylinder mode.

View attachment 378246

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My POS van is an 05, so no afm/dod. Thx for the pic. So if that bypass plugs it could cause a low oil pressure issue in the motor? Or just shows low oil pressure to the gauge? Sorry, not trying to hijack your thread op.

For your 4L65, there is actually a lot you can do without a full rebuild. The 3-4 circuit has a lot of potential leaks that cause premature failure of these transmissions. Most can be addressed without a full rebuild. I did quite a bit of research over at LS1tech. There are some amazing individuals there that have a lot of knowledge of these 4l6x transmissions. I did a full rebuild on my 190k 4L65 and was surprised at how little wear I found. I tow a 6000lbs travel trailer in the mountain west. I had Blackbear tune the transmission and also installed a corvette servo prior to my rebuild. That may be why my wear was limited. An example of some things that can be done with the pan off, see This Tread. Best of luck. I am on the tail end of my LQ4/4L65 rebuild. It is a journey to say the least, but has been fun learning from everyone.

Tonyrodz said:

My POS van is an 05, so no afm/dod. Thx for the pic. So if that bypass plugs it could cause a low oil pressure issue in the motor? Or just shows low oil pressure to the gauge? Sorry, not trying to hijack your thread op.

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Both, and neither
So it can increase backpressure against the oil pump. If the pressure builds up enough, which reduces flow through the engine because of the pump's own bypass valve, then you end up with a net decrease in oil volume which will appear as low pressure on the sending unit, even though pressure measured at the oil pump will be the same or potentially higher.

I'm thinking that this is over my pay grade. Thanks Buggdave for all the info and thread. Do you belive a mod 4l65e will be as durable as a 80e? However, it was like reading greek I didn't understand much, just that I need a lot of help and or a lot of money. I will look up the black bear tune. I most likely attempt to see if I can mate lq4 and 4l80e for better towing. I dont push the truck hard However, the trailer is heavy. I dont have the cash for a bigger Rig. 'm a travel icu RN and be working in Alaska next summer I need a rig that won't have a problem.

SnowDrifter said:

Both, and neither
So it can increase backpressure against the oil pump. If the pressure builds up enough, which reduces flow through the engine because of the pump's own bypass valve, then you end up with a net decrease in oil volume which will appear as low pressure on the sending unit, even though pressure measured at the oil pump will be the same or potentially higher.

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Forgot to mention, I had a Melling HV oil pump installed. Oil pressure was great until recently.

JohnnyA said:

I'm thinking that this is over my pay grade. Thanks Buggdave for all the info and thread. Do you belive a mod 4l65e will be as durable as a 80e? However, it was like reading greek I didn't understand much, just that I need a lot of help and or a lot of money. I will look up the black bear tune. I most likely attempt to see if I can mate lq4 and 4l80e for better towing. I dont push the truck hard However, the trailer is heavy. I dont have the cash for a bigger Rig. 'm a travel icu RN and be working in Alaska next summer I need a rig that won't have a problem.

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A 4l65E(Which is a 4L60E upgraded) is nothing like a 4L80E. A 4L60/65 are the "advancement" of the old TH700R4 and are rated for 6,000lbs (Hence the 60 in 4L60E) and the 4L80E is the advancement of the old TH400R which is rated for 8,000 lbs (Hence the 80 in 4L80E). The 4L60E has 1 band (2-4 band) and the 4L80E has 2 bands (Front and Reverse). The 4L80E(236lbs) is heavier than 60E(150lbs). The 4L80E is longer (by 2.9") than 60/65E so a driveshaft change is needed when swapped in. They both have overdrive. But they are very different animals. The 4L80E is made for towing. Works well in a road racer too. The 4L80E will bolt right up to your 6.0L Bellhousing and are stock in 3/4 and 1 ton 6.0/6.2L equipped truck chassis.