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That saddens me a bit but I totally understand. Collecting and editing and sharing this info is especially tiring when it feels like your shouting into the void.
I have read every word in this thread, several times over, and glean a new detail each time. I am still processing the data from our conversation 2 weeks ago.
I wish I could contribute more, but currently overwhelmed with work and learning a great many stinging lessons on how not to run a transmission building business.
I would however, love to hear the details about the oil pocket. I'm always delighted to hear how wrong I am in my intuition about hydraulic principles haha
i love this....I will have a 4L80 someday .....and will be looking and looking and looking at this thread .....to make sure i follow your advice to the T !
lots of useful info here and on this site....the worst part is tracking it down as it is here n there n everywhere.....wish we had a central ....how to do it ...guide
Originally I joined this forum to learn more about LS engines. I am doing a SI0 LS swap. I retired from rebuilding transmissions full time in 2007 and got bored by 2011. I started to run a small performance oriented bench rebuilding center for 4L60E's and 4L80E's.
I am in awe of the work that @vorteciroc has put into this post and I have a great respect for your knowledge. More will read this than you think, they may be like me. I come back to this transmission section because of you and @MaroonMonsterLS1. I accumalate tid bits of information every time I come back to catch up. Personally I don't post much because my knowledge is far less that the two of you. I know it is frustrating at times explaining over and over again, please keep up the good work. Both of you are helping people more than you know.
Damn! I completely understand being overwhelmed with work and not having time to post here. I was wanting more info on the pocket pump mod. Over the years I’ve seen several broke pump gears with fixed- high pressure 4l80’s. Wondered if it’s a cavitation or lube issue.
Originally I joined this forum to learn more about LS engines. I am doing a SI0 LS swap. I retired from rebuilding transmissions full time in 2007 and got bored by 2011. I started to run a small performance oriented bench rebuilding center for 4L60E's and 4L80E's.
I am in awe of the work that @vorteciroc has put into this post and I have a great respect for your knowledge. More will read this than you think, they may be like me. I come back to this transmission section because of you and @MaroonMonsterLS1. I accumalate tid bits of information every time I come back to catch up. Personally I don't post much because my knowledge is far less that the two of you. I know it is frustrating at times explaining over and over again, please keep up the good work. Both of you are helping people more than you know.
TranzMan, I really appreciate that!
Thank you!
I am a firm believer that experience can not be replaced by knowledge (especially not alone!)
Your experience has tremendous valve... anyone with really experience should be considered of value.
So Thank You again!
Damn! I completely understand being overwhelmed with work and not having time to post here. I was wanting more info on the pocket pump mod. Over the years I’ve seen several broke pump gears with fixed- high pressure 4l80’s. Wondered if it’s a cavitation or lube issue.
BadAss68, Thank you!
I appreciate your post!
MaroonMonster and I were comparing notes, regarding this Pump "Pocket" Modification.
Essentially, we both copy the THM400 Front Pump half casting (ending with) #895.
This is the "Late" THM400 Pump design.
We apply it to the "Early" THM400 Pump and the 4L80E Pumps.
What we were talking about was a slightly differently done Modification. commonly done to the Aluminum-PowerGlide Pumps.
(Essentially drilling a small hole from a Line-Pressure passage into the area that houses the Pump-Gears)...
(and putting some pressure one the "back-side" of the Pump-Gears to reduce/ limit Pump wear and tear).
I have used a combination of both the "Drilled-Hole and the "Pocket" for both the THM400 and 4L80E Pumps.
MaroonMonster's experience was invaluable, as he has had success with the "Pocket" modification ONLY.
So I have decided to follow his Model, and no longer also drill the Hole.
I appreciate the time he has spent testing this Modification in comparison to my own...
and I am very happy thus far with my findings (via his method).
We can always learn something new from one another...
and thus is my reasoning for partaking in these Forums (as apposed to hording all this knowledge and hiding it as my family members in Pro Drag-Racing did).
I do Not see you often on the Forum... But Obviously you are reading from time to time.
Thank you for all of your own contributions to both the THM200-4R and the 4L80E (that now has your shop super busy!)
I am very Glad to see your success with all the 4L80E work!
It has been a pleasure discussing some technical information with both of you!
I am glad to see that both of you have been completing projects with a tiny bit of my input and knowledge!
I just acquired an early 4L80E. 1996 year. It had a broken case, so I picked up a replacement case. I plan to build this for mild performance applications. If it helps I can build this ever so ssssllllloooowwwwlllyyyy.... Could be fun...
I am a retired fleet auto tech and not a pro trans builder. I have built a fair amount of stock transmissions and a few
hi-performance units over my 39 year carrier. Most of the hi-performance units that I built were th350s back in the day and 4L60Es. For some reason I have only had the opportunity to build one th400 and one 4L80E. This is the main reason that I am not very active in the 4L80E discussions, but you can rest assured that I am reading and taking notes. I am always down to learning all I can to increase my knowledge about transmissions. Thank you @vorteciroc, MaroonMonster, TruckDoug and PBA for being so willing to share your knowledge.
Last edited by bbond105; Mar 31, 2021 at 09:25 AM.
I consider this a more significant Lube Modification!
This is something that I consider to be Mandatory for any 4L80E with Fixed High Line-pressure or a Trans-Brake.
Very briefly I wish to mention a design improvement that GM/ Hydra-Matic Engineers made to the Late design THM400 Pump.
I mention this, because the modification I will show next... comes from a STOCK improvement that GM created for the THM400.
Here is an image of the Late design THM400 Front half (Casting number ending in: 895) of the Pump:
The Blue Circle on the image above shows a small gap between the Outer Pump-Gear and the Pump Casting.
This small gap is referred to as a "Pocket" and it is for Oil to collect and help prevent excessive Pump Gear wear and tear.
I am not going to discuss the how/ why this works until later.
Both the Early design THM400 Pumps and all of the 4L80E Pumps lack this "Pocket" that is shown in the Blue Circle.
So, we modify the 4L80E Pumps (and Early THM400 Pumps) to have this pocket made via a simple milling process.
Thanks to Maroon Monster again for the next image that follows.
The next image shows the same pocket, but with the Pump Gears removed.
Shown below inside the Red square:
This Modification should be performed on all 4L80E units that have Fixed Line-Pressure or a Trans-Brake.[/QUOTE]
Looking into this modification in general. You said GM added it to all production 400 pump bodies. I only remember that being in some pump bodies and not others. I was in a production facility rebuilding stock replacements. The only lube experiment we tried was full time feed. We scrapped the modification when we saw cooler pressure rise from 60psi to over 100psi at idle on a dyno. We made an assumption that it would add to thrust issues in the 400 and we didn't need more of that. Is that maybe why TransGo and others say to only drill full time feed to .055? Performance always takes everything to another level.
As long it is on the suction side of the outer pump gear. Do you as an engineer think the placement of this groove is critical? I noticed that the groove in the 400 pump body in the picture does not go to the bottom of the pump gear pocket. I remember that they did. Maybe my memory isn't very good. Do you think it should or is it not critical to the actual function. Why not use it in all performance units?
I remember cutting the crescent on the pressure side of 350/400 pump for pump whine. If you cut it to shallow or narrow, the modification did not have any effect on the whine.
I just acquired an early 4L80E. 1996 year. It had a broken case, so I picked up a replacement case. I plan to build this for mild performance applications. If it helps I can build this ever so ssssllllloooowwwwlllyyyy.... Could be fun...
excellent score! the '96-'97 units are seemingly rare these days
Not so much!
