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

spm1us · October 1, 2023

Be aware that the exhaust pipe heat wrap is known to cause rapid deterioration of the metal tubing from constant heating/cooling cycles and accompanying condensation.
Proceed at your own risk!!!

64BAwagon · October 1, 2023

44 minutes ago, spm1us said:

Be aware that the exhaust pipe heat wrap is known to cause rapid deterioration of the metal tubing from constant heating/cooling cycles and accompanying condensation.
Proceed at your own risk!!!

It was widely used on almost every diesel truck we had at work. Many of them were 15+ yrs old and I never once saw any deleterious effects from it.

spm1us · October 1, 2023

I don’t deny it’s sold and used in many applications but just google header wrap and headers and judge for yourself. IYKTYK

Grumpy Bear · October 2, 2023

12 hours ago, spm1us said:

Be aware that the exhaust pipe heat wrap is known to cause rapid deterioration of the metal tubing from constant heating/cooling cycles and accompanying condensation.
Proceed at your own risk!!!

Header Wrap: What You Should Know About Wrapping your Pipes (chevyhardcore.com)

Give that some more thought. What effect does a wrap have on the NUMBER of cycles? NONE!

What effect does it have on the final temperature of cool down. NONE!

What effect does it have on the rate of cool down? A bunch. Much slower and less stressful.

Have used wrap on an off for 50 PLUS years. Have never experienced a single issue. 90% of my headers were mild steel.

Mike Heartburn · October 14, 2023

I just want to say to the OP, Epsilon Plus thank you for your concise instructions and part numbers. I was able to install my dipstick in less than 30 mins.

I originally was looking into this because my transmission was clunking on downshift in my 2020 Silverado 2500 HD WT with a 6L-90. I use it to tow a fairly light 5th wheel and only have 16k miles on it. With so few miles, I wasn’t interested in a pan drop and filter replacement so soon. Adding the dipstick allowed me to suck out about 50% of the old fluid (5qts) and add some fancy cherry flavored juice from Amsoil.

No more clunking and now shifts like butter. Thank you - Mike

Pryme · October 15, 2023

18 hours ago, Mike Heartburn said:

I just want to say to the OP, Epsilon Plus thank you for your concise instructions and part numbers. I was able to install my dipstick in less than 30 mins.

I originally was looking into this because my transmission was clunking on downshift in my 2020 Silverado 2500 HD WT with a 6L-90. I use it to tow a fairly light 5th wheel and only have 16k miles on it. With so few miles, I wasn’t interested in a pan drop and filter replacement so soon. Adding the dipstick allowed me to suck out about 50% of the old fluid (5qts) and add some fancy cherry flavored juice from Amsoil.

No more clunking and now shifts like butter. Thank you - Mike

Did you suck it out with a mityvac? So is the amsoil fluid fully compatible with the stock stuff?

Grumpy Bear · October 15, 2023

1 hour ago, Pryme said:

So is the amsoil fluid fully compatible with the stock stuff?

Yes.

Mike Heartburn · October 15, 2023

2 hours ago, Pryme said:

Did you suck it out with a mityvac? So is the amsoil fluid fully compatible with the stock stuff?

Oddly enough my truck has a factory drainplug at the back of the transmission, it allowed me to drain out about 2qts. Then since I'm a cheap SOB, I sucked out the rest with a shopvac, flexible tubing, and a 64 oz glass jar. It took a while and if I had to do it again I'd probably do it differently.

Amsoil swears up and down their Pro Series cherry juice is compatible with just about everything.

Epsilon Plus · October 21, 2023

On 10/15/2023 at 8:06 AM, Mike Heartburn said:

Oddly enough my truck has a factory drainplug at the back of the transmission, it allowed me to drain out about 2qts. Then since I'm a cheap SOB, I sucked out the rest with a shopvac, flexible tubing, and a 64 oz glass jar. It took a while and if I had to do it again I'd probably do it differently.

Amsoil swears up and down their Pro Series cherry juice is compatible with just about everything.

That drain plug is actually a fluid level check plug for the cockamamie way they want you to check fluid level without a stick.

PML has custom stock height (5/8 deeper) and deep pans for our trucks with a proper magnetic drain plug.

https://yourcovers.com/pml-gm-6l90-6l90e-deep-transmission-pan.html

I don't think the extra pan depth would affect fluid level reading as the extra capacity is physically lower than where the stock low point would be. Does that make sense? Be nice if they made a 2019 pan without the extra level check hole of the 20+ (leak point).

64BAwagon · October 27, 2023

Has anyone seen a new pan for the L8T 10 speed combo ? There are offerings for the diesel/10 spd combo but the pan for the gas engine 10 spd is different due to the exhaust. If I dont find a replacement pan I will likely install a drain plug in my stock one during the first service but a couple extra qts of capacity wouldnt hurt.

DHBWA · November 22, 2023

I tried installing a dipstick on my ‘19 1500 and no way … Tried and tried…Thought I had it coming from the bottom but still no go. I wonder if the HD models have just a touch more clearance between the cyl head and firewall?? B

mtbadbob · November 24, 2023

On 10/27/2023 at 7:27 AM, 64BAwagon said:

Has anyone seen a new pan for the L8T 10 speed combo ? There are offerings for the diesel/10 spd combo but the pan for the gas engine 10 spd is different due to the exhaust. If I dont find a replacement pan I will likely install a drain plug in my stock one during the first service but a couple extra qts of capacity wouldnt hurt.

I bought the GM dipstick for my '22, but just traded it in on my '24 w/Allison before I ever installed the stick. I'm also curious if the stick will work on the Allison, or if the 10 speed has one. I'll have to investigate soon as I haven't even looked under the hood yet!

Edited November 24, 2023 by mtbadbob

64BAwagon · November 24, 2023

@mtbadbob The Allison doesnt have provisions for a dipstick like the 6 speed did.

I posted about how to use a fitting and a hose to refill the sump without having to pump up into the case. It simplifies the process of a spill and fill. My plan is to either replace the trans pan with one that has a drain plug or install a drain plug on the original one. I use this method on my cars that have drain plugs. I drain the fluid and calculate how much came out then replace that amount( 4.3 qts) . Once youve determined the trans is full by going through the ridiculous process of checking it, you can then use this method assuming you have no evidence of a leak.

That way I could change out fluid with less work. So far I have not seen a replacement pan for the gas engine applications but I am confident someone will bring one out soon.