front pump seal

[santon]

1997 GMC Yukon 4WD, I noticed a drop of ATF at the bellhousing. There are no paddles under the truck. The transmission shifts fine. The truck has 217k km on the odometer. Is it a front pump seal? Do you guys think I can monitor the ATF level and drive the vehicle meanwhile?

 

[Mooseman]

Sure. The 4L60 is known to develop leaks at the front pump/torque converter seal. You could keep driving it like this and keep an eye on the fluid level but it will likely come to a point you'll have to drop the tranny and replace that seal or even rebuild it.

 

[santon]

The truck was sitting for most of its life. The previous owner used to drive on weekends only. Somebody told me to try to add the additive to revitalize the seal. Is it worth trying?

 

[Mooseman]

You could try but follow the directions carefully. I don't have experience with additives for leaks but I have had great results from Lubegard for the shuddeer fixx. Got this from AI:

For a GM 4L60E transmission experiencing leaks, especially in older or high-mileage units, the most highly recommended and commonly used additives are Lucas Oil Transmission Fix and ATP AT-205 Re-Seal. These products are designed to condition hardened seals and stop leaks without damaging the internal components of the 4L60E.
Here are the best options based on user feedback and product specifications:

Top Recommended Additives for 4L60E

• Lucas Oil Transmission Fix (24 oz): Widely regarded for its ability to stop seal leaks while also reducing slip and, in some cases, hesitation and rough shifting. It is a non-solvent formula that works well for high-mileage transmissions.
• ATP AT-205 Re-Seal (8 oz): Often praised for being a fast-acting, professional-strength sealer that restores rubber seals to their original size and flexibility. It is safe for all types of automatic transmission fluids (ATF).
• Liqui Moly ATF Additive (250 ml): A highly rated option for cleaning internal passages and keeping rubber/plastic seals soft and pliable. It is particularly useful for reducing noise and improving shift performance.
• Lubegard Red ATF Protectant: Recommended by professional transmission rebuilders for use with DEXRON-III or DEXRON-VI fluids. It helps to condition seals and improve shifting.

Tips for Using 4L60E Leak Fix Additives

• Application: These additives can generally be added directly to the existing transmission fluid through the dipstick tube, with no need to drain fluid first.
• Effectiveness: These products are best for minor leaks caused by dried or brittle seals. If the leak is caused by a torn, ripped, or physically damaged seal, an additive will likely not be a permanent fix.
• Prevention: These products can also be used as preventative maintenance to keep seals pliable.

 

[santon]

I called some shop, and the mechanic told me that sometimes the problem is not only the front seal but also the torque converter and some bushings, so this bushing must be replaced together with the front seal, and the torque converter must be rebuilt. Which bushing is this? Is it indeed so? The truck was sitting in the parking lot for 3-4 days, and today I found an ATF stain under the transmission. Still thinking about trying an additive.

 

[santon]

I think I see some ATF on the bellhousing, but I also noticed ATF on some bolts of the pan gasket (a couple of front bolts and maybe one on the front right corner). The previous owner also told me that the pan gasket must be replaced. Maybe it is just the gasket?

 

[Mooseman]

Maybe it is just the gasket?

Quite possible. If it's the cork style gasket, it is more prone to leakage. Another possibility is the pan bolt holes were deformed by the last person to drop the pan by over-torquing the bolts, which is quite easy with a cork gasket. The best gasket is the OEM style rubber/metal type. They are so good that they are reusable.

 

[santon]

Quite possible. If it's the cork style gasket, it is more prone to leakage. Another possibility is the pan bolt holes were deformed by the last person to drop the pan by over-torquing the bolts, which is quite easy with a cork gasket. The best gasket is the OEM style rubber/metal type. They are so good that they are reusable.

I think the old gasket is a cork. The previous owner gave me the filter and gasket kit, GM #24236799. According to the Autozone website, the gasket in this kit is made from Farpak material. I will drop the pan this weekend and replace the filter and the gasket. Do you recommend adding some RTV?

 

[Mooseman]

No RTV. It's installed dry.

 

[santon]

I replaced the filter and the pan gasket. Now I dont see ATF on the bellhousing or on the gasket bolts. The only wet area is around the selector swtch. It has a orange silicone gasket, the gasket is wet. What should be replaced, this gasket or the shaft seal?

 

[Mooseman]

I have never dealt with that seal so I don't know. The one you see from the outside may just be an external dirt/water seal.

I did find this video that shows the process very well. It does require a specialty tool.

 

[santon]

I have never dealt with that seal so I don't know. The one you see from the outside may just be an external dirt/water seal.

I did find this video that shows the process very well. It does require a specialty tool.

Ordered the tools and the seal; will try to replace it. Thanks!

 

[santon]

I have never dealt with that seal so I don't know. The one you see from the outside may just be an external dirt/water seal.

I did find this video that shows the process very well. It does require a specialty tool.

I replaced the seal today. With the special tool, it was an easy job. It seems like it fixed the leak. Thanks a lot, Mr. Mooseman!

There is an additional small leak under the transfer case. I see drops of ATF on the shield of the transfer case. Cannot figure out the exact place of the leak. What are the most common places of the leak there?

 

[Mooseman]

Could be the output shaft seal from the tranny. That's the only one I can think of that would be leaking tranny fluid unless the Transfer Case is using other than the blue fluid that it's supposed to use and it's leaking.

 

[movietvet]

I replaced the filter and the pan gasket. Now I dont see ATF on the bellhousing or on the gasket bolts. The only wet area is around the selector swtch. It has a orange silicone gasket, the gasket is wet. What should be replaced, this gasket or the shaft seal?

Keep an eye on that pan gasket you replaced. @Mooseman mentioned deformed transmission pan bolt holes in the #8 post, caused by a previous over tightening on the transmission pan bolts, likely during a transmission service. If you did not flatten the holes back level, they are still deformed. When the pan is dropped, you take a small ball peen hammer and use the flat surface and tap the holes down to where they are flat again. This is done from the gasket side of the pan. You want to use the flat part of the hammer because using the ball side will deform the holes to the other side. You will know you have them flat by using your hand to rub across the holes or lay the pan down on a flat surface, like glass or a stainless steel top on a tool box or even using a straight edge tool. Then, during reassembly, you torque the pan bolts to the proper torque.