Advice Please: Planning 4L80 Conversion

[Mogman]

I have an M1123 so I think it comes with a 4L80? Looks to be in rough shape. Would a 6L80 bolt right into the same spot and also if I put a 6.2 LS in there can the transmission stay where it is and I mount the motor and build motor mounts to it or does the whole combo need to move around?

Here is my build thread NO it will not just bolt up, but it is doable, probably not practical unless you have a fully equipped shop.

6L80 in my M998

EDIT, as you read this thread I ended up using a 6L80 as the 6L90 was toast and the 6L80 has the same output shaft as the 4L80/3L80. I was at a machine shop auction the other day and picked up a 6L90 with a MP1626XHD transfer case, it is complete with T/C, the front shaft, cooler lines and shift...

www.steelsoldiers.com

 

[springer1981]

Springer1981, please tell me about the fan kick down switch relocation parts, where you got them etc. That's one thing I still need to do from my 4l80e conversion.

You either need the complete switch "kit" that has the switch and bracket (5 in the picture) you already have and a Rod ( and Clip (9) you need. In addition to the kit you also need a relocation bracket (10).

The kit is expensive and all you really need is the rod and clip.
https://www.ebay.com/itm/184562882620

Here is the bracket you need
10 Bracket 12460125

EC12460125 / 01-473-8626 5340-01-473-8626 - BRACKET, FAN SWITCH | Hummer Parts Guy (HPG)

www.hummerpartsguy.com

If you call hummerpartsguy and ask them about these 2 parts, they might have them and you just use your switch.
8 Rod 12460124 / 3040-01-411-4191

12460124 / 01-411-4191 3040-01-411-4191 - ROD, FAN SWITCH | Hummer Parts Guy (HPG)

www.hummerpartsguy.com

9 Clip 12460160 / 5340-01-439-1156

EC12460160 / 01-509-9613 5340-01-509-9613 - CLIP, FAN SWITCH | Hummer Parts Guy (HPG)

www.hummerpartsguy.com

 

[springer1981]

I forgot to mention that I couldn't get the clip and used a dab of silicone to hold it. Also I think I have a used setup (switch, rod, relocation bracket) less the clip if your interested.

 

[kzeyus]

I forgot to mention that I couldn't get the clip and used a dab of silicone to hold it. Also I think I have a used setup (switch, rod, relocation bracket) less the clip if your interested.

pm sent

 

[FlameRed]

I would like to post more questions on the 4L80 conversion. I picked up that 4L80, along with the transmission cross-member, mount, 242 gearbox, and torque converter.

The torque converter is really, really rusty. I can try to clean it up and paint it. I looked down the inside and it looks nice an shiny, I don't see rust on the inside. Is it too far gone and should I get a new one?



What is the best way to connect the 4L80 cooling lines up to the M998 cooling fittings. Is rubber hose and clamps hold up? AN fittings? Something else?

When I got the stuff home, I noticed a nail from the palette it was on punctured the tranny pan. I don't weld, but I could take the pan somewhere and have it tig welded up, or better still have them weld in a oil drain. I planned on changing out the transmission filter anyway. I was kind of surprised that there was no oil drain on the 4L80 like there was on the M998.

I'll probably have many more questions. Thank you in advance for your advice.

 

[Maxjeep1]

I don’t know about the rusty stub going into the new seal? New pan with drain plug and gasket is 75.00 on HPG site. Probably find it even cheaper. I would be curious if the Humvee stall is the same as normal torque converter?

 

[springer1981]

I don’t know about the rusty stub going into the new seal? New pan with drain plug and gasket is 75.00 on HPG site. Probably find it even cheaper. I would be curious if the Humvee stall is the same as normal torque converter?

No, different stall for Diesel engines.

 

[springer1981]

What is the best way to connect the 4L80 cooling lines up to the M998 cooling fittings. Is rubber hose and clamps hold up? AN fittings? Something else?

The lines on the truck don't change. The lines to and from the transmission cooler are the same and are mounted to the frame rails. Then there are rubber lines that connect to the metal lines on the transmission assembly. Simply remove the rubber lines from the metal lines attached to the frame rail under the truck. Then after you mount the 4spd transmission the lines connect back to the same metal lines with hose clamps. You need to study the TM's. ALL the information is there.

 

[FlameRed]

Another followup question regarding the 4L80E conversion.

I have been told that I might need a different fuel tank to install the 4L80E? I have been told there are two different fuel tanks. The one that has an X embossed on the bottom is the one needed for the 4L80, and the other one without this will either require some modification or swapped out for the one with the X.

Can anyone tell me what modification needs to happen on the tank that does not have the X?

 

[Retiredwarhorses]

You either need the complete switch "kit" that has the switch and bracket (5 in the picture) you already have and a Rod ( and Clip (9) you need. In addition to the kit you also need a relocation bracket (10).

The kit is expensive and all you really need is the rod and clip.
https://www.ebay.com/itm/184562882620

Here is the bracket you need
10 Bracket 12460125

EC12460125 / 01-473-8626 5340-01-473-8626 - BRACKET, FAN SWITCH | Hummer Parts Guy (HPG)

www.hummerpartsguy.com

If you call hummerpartsguy and ask them about these 2 parts, they might have them and you just use your switch.
8 Rod 12460124 / 3040-01-411-4191

12460124 / 01-411-4191 3040-01-411-4191 - ROD, FAN SWITCH | Hummer Parts Guy (HPG)

www.hummerpartsguy.com

9 Clip 12460160 / 5340-01-439-1156

EC12460160 / 01-509-9613 5340-01-509-9613 - CLIP, FAN SWITCH | Hummer Parts Guy (HPG)

www.hummerpartsguy.com

View attachment 877129

its easier to add the switch to the pump as they do on the turbo engine….

 

[Retiredwarhorses]

Another followup question regarding the 4L80E conversion.

I have been told that I might need a different fuel tank to install the 4L80E? I have been told there are two different fuel tanks. The one that has an X embossed on the bottom is the one needed for the 4L80, and the other one without this will either require some modification or swapped out for the one with the X.

Can anyone tell me what modification needs to happen on the tank that does not have the X?

You can’t modify an early tank….and you wouldn’t want to, the cost of a new tank is negligible, and it’s a good time to refresh what now 30yrs old.

 

[FlameRed]

Another followup question regarding the 4L80E conversion added to my list:

• Can anyone tell me what modification needs to happen on the fuel tank that does not have the X embossed on the bottom?
• Should I use Dexron 6 fluid in the 242 gearbox or GM Manual Transmission and Transfer Case Fluid 88861800

 

[Mogman]

GM Manual Transmission and Transfer Case Fluid 88861800 is for cast iron transmissions and transfer cases, it is gear oil and should not be used in an aluminum transfer case.
I use DEX III but many use DEX VI

 

[Coug]

Another followup question regarding the 4L80E conversion added to my list:

• Can anyone tell me what modification needs to happen on the fuel tank that does not have the X embossed on the bottom?
• Should I use Dexron 6 fluid in the 242 gearbox or GM Manual Transmission and Transfer Case Fluid 88861800

DEX 3 is what GM recommends for non-automatic transmission applications. They have a manual gearbox fluid that is basically just DEX 3, but not sure what their part number for it is.

 

[Vapor Trail]

I've got a 4L80E and fuel tank in my M1123 I'll be selling. I'm not ready to take it out yet but if you're interested send me a PM. Might sell the prop shafts and drive shaft too.

 

[Coug]

GM Manual Transmission and Transfer Case Fluid 88861800 is for cast iron transmissions and transfer cases, it is gear oil and should not be used in an aluminum transfer case.
I use DEX III but many use DEX VI

I thought that the 88861800 was supposedly repackaged DEX III fluid.
Looking at the label, it even says it contains automatic transmission fluid (along with other oils)




Then here is what I found on another site.

Originally Posted by GM #04-07-30-037D
MANUAL TRANSMISSIONS / TRANSFER CASES and POWER STEERING

Any vehicle that previously required DEXRON®-III for a manual transmission or transfer case should now use P/N 88861800. This fluid is labeled Manual Transmission and Transfer Case Fluid. Power Steering Systems should now use P/N 9985010 labeled Power Steering Fluid.

Consult the Owner's Manual or Service Information (SI) for fluid recommendations.

Some of our customers and/or General Motors dealerships/Saturn Retailers may have some concerns with DEXRON®-VI and DEXRON®-III Automatic Transmission Fluid (ATF) and transmission warranty claims. DEXRON®-VI is the only approved fluid for warranty repairs for General Motors transmissions/transaxles requiring DEXRON®-III and/or prior DEXRON® transmission fluids. Please remember that the clean oil reservoirs of the J 45096 - Flushing and Flow Tester machine should be purged of DEXRON®-III and filled with DEXRON®-VI for testing, flushing or filling General Motors transmissions/transaxles.

DEXRON®-VI can be used in any proportion in past model vehicles equipped with an automatic transmission/transaxle in place of DEXRON®-III (i.e. topping off the fluid in the event of a repair or fluid change). DEXRON®-VI is also compatible with any former version of DEXRON® for use in automatic transmissions/transaxles.



image near the top taken from https://www.amazon.com/Genuine-Fluid-88861800-Manual-Transmission/dp/B00BK7M1EK

The service bulletin portion was found at the below link, and the image below was found there as well

DextronIII vs Dextron VI - CorvetteForum - Chevrolet Corvette Forum Discussion

C5 Tech - DextronIII vs Dextron VI - I've had conflicting answers on whether or not Dextron VI is suitable for the 99 C5 standard transmission. Can anyone advise Thank you

www.corvetteforum.com

 

[Mogman]

I of course could be wrong, here is where I got my info.

ACDelco 88861800 ACDelco Manual Transmission Fluid | Summit Racing

Free Shipping - ACDelco Manual Transmission Fluid with qualifying orders of $109. Shop Transmission Fluid at Summit Racing.

www.summitracing.com

 

[Coug]

So you learn something new every day.

According to Royal Purple, GM 88861800 can be replaced with either their HPS or XPR 5W-30 OR their Max Gear 75W-90.

Reading up somewhere else, the "gear oil" weights are actually basically the same as motor oil weights, but they use a different scale/numbering system so people don't confuse bottles of gear oil and motor oil, which could lead to some pretty expensive repairs as gear oil and motor oil, even if the same weight, use completely different additive packages in them.

Is 75w90 the same as dexron 3 atf??? - CorvetteForum - Chevrolet Corvette Forum Discussion

C6 Tech/Performance - Is 75w90 the same as dexron 3 atf??? - I'M LOOKINGTO CHANGE MY TRANNY FLUID AND MY REAR DIFF FLUID ON MY 2005 C6 VERTE M6 LS2 WITH MAGNUSON S/C AND I SEE THAT THE REAR DIFF TAKES 1.8 QUARTS OF 75W90, AND THE TRANNY TAKES 4.1 QUARTS OF DEXRON 3 ATF. I'M LOOKING TO USE THE...

www.corvetteforum.com

http://www.royalpurple.com/wp-content/uploads/2019/01/Royal_Purple_Transmission_Reference.pdf

 

[Mogman]

Gear oil is much thicker than ATF , as far as I can remember the viscosity weights are directly related from gear oil to automatic transmission fluid to engine oil.

 

[Coug]

Gear Oil vs. Engine Oil: What's The Difference? - AMSOIL Blog

When looking at gear oil vs engine oil, their viscosity ratings and additives are two primary things to keep in mind.

blog.amsoil.com