Installing a transmission dipstick for the 6L90 (L8T gas trucks) using factory fit GM parts.

mtbadbob · December 13, 2022

On 10/31/2022 at 10:29 AM, Epsilon Plus said:

My truck @ 7,200mi was about 1/2 quart low BTW. Not surprised after reading about these trucks shipped dry on front end grease and low in the diffs.

So, all new HD's are shipped w/o trans dipsticks from the factory??

ssgballistics · December 14, 2022

2 hours ago, mtbadbob said:

So, all new HD's are shipped w/o trans dipsticks from the factory??

Correct, no trans dipstick. They have a check plug on the trans pan.

64BAwagon · December 14, 2022

16 hours ago, mtbadbob said:

Get the MBRP cat-back system for under $500. $ well-spent & lose about 30 lbs!

The problem is that its not a stainless system at that price and living in the rust belt where road salt is a religion to the road crews the stainless is a necessity.

mtbadbob · December 15, 2022

13 hours ago, 64BAwagon said:

The problem is that its not a stainless system at that price and living in the rust belt where road salt is a religion to the road crews the stainless is a necessity.

The stainless runs about another $400 I think.

64BAwagon · December 15, 2022

For me the 3 1/2" system is fine. I just want a little more sound and to remove the restrictive muffler. Unless someone comes up with a direct fit muffler that I can use to swap out the OEM one I likely wont do anything with the exhaust. I have to believe that at some point one of the exhaust manufacturers will see the potential market for that.

mrjulian416 · December 16, 2022

On 10/28/2022 at 8:19 AM, Epsilon Plus said:

Now as far as a proper hot check, I've always used a minimum transmission temperature of 145'F. The GM check procedure for these trucks says 86'F-122'F, but that's using the inane check plug thingy on the back of the transmission pan. Previous to that design, the hot check temp for Dexron VI was always 145'F min to 190'F max (ATF expands with heat). Perhaps there is someone out there with a service manual for a 2019 and can verify, but there you go folks.

Back to the subject at hand...

First off, thank you for this write-up and parts list. The Haynes guys say to check at "normal operating temperature".

2015-19 HD fluid check procedure vid

Edited December 16, 2022 by mrjulian416
typo

mtbadbob · December 17, 2022

On 12/13/2022 at 5:27 PM, ssgballistics said:

Correct, no trans dipstick. They have a check plug on the trans pan.

I went ahead & ordered everything from RockAuto for under $50 shipped so I guess I'll be installing it soon!

Core-Lokt · January 7, 2023

Did it yesterday. For me, it was a 15-minute job, mainly because my truck was clean and new.

Randal Scott · February 16, 2023

Hey, AFE power makes a cat-back kit made of stainless steel. But it is 409 stainless steel, not 304.

Randal Scott · March 12, 2023

Thanks for the info on the Dipstick install!

Edited March 12, 2023 by Randal Scott

Pryme · March 31, 2023

Just ordered these parts. Will be my next project.

Thanks for the part numbers guys.

Pryme · April 5, 2023

Okay so I installed mine this evening.

I’m glad I did this on a perfectly clean truck vs trying to do this with a bunch of dirt and mud etc.

it sure is tight quarters reaching up to put the flange nut on up between the cat and trans.

this thing sure does stick out into the engine bay. I took a few pics, but it appears the others who shared pics are in the same spot. Only goes one way.

Do you guys find the dipstick sure takes some fanagling to get it down the crazy S shaped bends.

my truck was bone cold and it appears the fluid level is way up on the dipstick past the full hot. The cold is way lower.

what did you guys experience? I will check after a drive tomorrow.

Edited April 5, 2023 by Pryme

Pryme · April 5, 2023

Pryme · April 5, 2023

64BAwagon · April 5, 2023

Your right about it being hard to reinsert. I wondered if it might get a little easier as time went on but I ended up selling my truck in February so I wont know if it does.

On this truck the only time to check it accurately is at full temp when the cooler thermostat opens. On a stock truck its 194 but if one of the bypass kits is installed the reading should be accurate at any temp with the truck running.

I made note of my reading at a cold non running state just for service reference to get a baseline after a pan drop.