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

Pryme · April 5, 2023

6 minutes ago, 64BAwagon said:

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.

Yeah my cold non running level seems high but I have yet to check it while running and running at temp for that matter.

Didn’t you order a 24? wonder if they have a trans dipstick kit for the 10spd

Edited April 5, 2023 by Pryme

64BAwagon · April 5, 2023

9 hours ago, Pryme said:

Yeah my cold non running level seems high but I have yet to check it while running and running at temp for that matter.

Didn’t you order a 24? wonder if they have a trans dipstick kit for the 10spd

Yes I have a 2024 on order. I already have a couple of things I want to look at to make it easier to service. It might not get a dipstick but I have a couple of ideas. Its sad that GM cheaps out and doesnt put a level sensor in this trans. I know the vast majority of the 3000 and 4000 series Allisons I used to maintain at work had the ability to check the fluid level via the touchpad. I got certified at one point as an Allison maintenance tech and their engineers typically did a good job of making maintenance as easy as possible (albeit expensive)on their big truck units.

Pryme · April 11, 2023

Checked mine while running and trans temp at 154. Was just inside the full hot hash marks. I’m calling that good.

it also seems to have learned it’s bend and was a little easier to put in.

glad I added it for the piece of mind.

64BAwagon · April 11, 2023

I was told that as long as its at the threshold where the trans fluid thermostat is open (I believe its now 154) then the level would be accurate.

carkhz316 · April 14, 2023

I just added one, but it must have gotten bent at one time, because it wouldn't line up for nothing. I had to bend it a few times so it would point in the "normal" spot in the engine bay. Thanks for whomever posted pictures. I was getting a little frustrated until I decided to just bend the tube.

Pryme · April 15, 2023

23 hours ago, carkhz316 said:

I just added one, but it must have gotten bent at one time, because it wouldn't line up for nothing. I had to bend it a few times so it would point in the "normal" spot in the engine bay. Thanks for whomever posted pictures. I was getting a little frustrated until I decided to just bend the tube.

That’s not good. Can you post a pic of how it sits in the engine bay? Is it the same as all the others posted?

carkhz316 · April 17, 2023

On 4/15/2023 at 7:28 AM, Pryme said:

That’s not good. Can you post a pic of how it sits in the engine bay? Is it the same as all the others posted?

I'll try and snap a pic. It wasn't my own inepitiude in installing. I could get in "in place" in about 10 seconds. but the bracket wasn't lined up with the 2'oclock bellhousing stud, and the tube was almost touching the firewall, hence why I suspected the tube was bent/ damaged at one point. I just had to tweak it a bit to get it to sit right and then all was fine.

carkhz316 · April 17, 2023

Here you go. I ordered the parts from Rockauto, and while they generally are pretty good about shipping, the tube was just flopping around in the box with my other parts, and jammed into the corners of the box, so it probably got pinched or squished at some point to get bent just a little bit to not line up properly. The paint was chipped off a bit by the bracket as well, suggesting that got bent. Oh well, its in now.

Pryme · April 17, 2023

4 hours ago, carkhz316 said:

Here you go. I ordered the parts from Rockauto, and while they generally are pretty good about shipping, the tube was just flopping around in the box with my other parts, and jammed into the corners of the box, so it probably got pinched or squished at some point to get bent just a little bit to not line up properly. The paint was chipped off a bit by the bracket as well, suggesting that got bent. Oh well, its in now.

Yeah if it works it works. It’s angled back more than mine and the others I’ve seen. Mine comes out over the ac line. I ordered from rock too. Mine was vacuum sealed in plastic and was kind of a pita to get out of it.

GMC AT4 · April 18, 2023

I found it real easy to run the tube up from the bottom to get it in place

carkhz316 · April 18, 2023

12 hours ago, GMC AT4 said:

I found it real easy to run the tube up from the bottom to get it in place

Getting it in place was fine. That took seconds to get the tube inserted into the transmission. My issue is that the overall tube was bent so the bracket wouldn't line up, and the tube was hitting the firewall initially.

Dunn · May 16, 2023

Great mod to do, amazing it doesn't come with it....

Trans stick for sure just for POM....

64BAwagon · July 18, 2023

Since I now have a 2024 with the L8T and the 10 spd Allison branded trans I am looking for a way to make this one easier to service. SInce this trans never came with a dipstick theres no way to add one (that I am aware of)

I am currently working on a setup to simplify the process of adding fluid after a service. I want to avoid the ridiculous process of pumping fluid into the case while the hot exhaust scorches my face.

The parts should be here in a week or so, I will post when I get them.

Hoginedgewood · September 30, 2023

Excelent details, been waiting for cooler weather, thanks for the heads up.

it's amazing how long the cat stays hot after just a few minutes to get the truck on the ramps.

64BAwagon · October 1, 2023

Since I was under the truck anyways I bought some 2" wide exhaust wrap and wrapped the pipe that crosses under the transmission pan. It didnt cost much at all and anything that keeps heat off of or out of the trans should help, I realize it may not have a big difference but why not try it. Seems kind of silly to run a screaming hot pipe just 3" away from a fluid pan.