Want to change running gear fluid

[Frankenchevy]

Hey, I’m looking at what it takes to do fresh fluids in diffs, tcase, and trans.

1. Correct me if I’m wrong on any of this...

TH400HD-Dexron 3

Np208-Dexron 3

14ff with Detroit locker-75w-90 GO of preferred brand

King Pin D60f with trac lok LSD-75w-90 GO with additive

2) I know asking which oil is problematic on a forum, but...

What do you guys like to run for the each of the oils and gaskets. I planned on sticking with Napa trans filter.

3) anything to look for other than metal pieces when the diff covers and trans pan are off?

As always, thanks a ton for your input!


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[Honky Kong jr]

I run Type F in my TH400

 

[twinturbo427]

I run Type F in my TH400

Only because you are shifty and too cheap to buy real B&M fluid.

 

[1987 GMC Jimmy]

I think you've got it all right. I think any filter you use will be fine. I'll always use the cheapest Dexron III I can find. Same for Type F if you wanted to go that route. I don't think the filter's a big deal. I'd find the cheapest one I could. Fram is the only brand to steer clear of when it comes to filters in general. I like to also cut open the filter to see what's in it in addition to looking over the magnet. I don't know if TH400s are like this, but 700R4s had a separate filter seal, and now they make them with an integrated seal so you had to pick the old one out of the valve body or the new filter won't seat properly. I don't know if the same applies, but the instructions should mention that if it is a concern.

 

[twinturbo427]

Hey, I’m looking at what it takes to do fresh fluids in diffs, tcase, and trans.

3) anything to look for other than metal pieces when the diff covers and trans pan are off?

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The brand is far less important than the actual maintenance. Changing the fluids is a great start, keeping them topped up regularly is important too.

On well used vehicles, or engines of unknown condition, I always do the first change with whatever I have on hand, or can find on sale. Then I use my brand or whatever is the correct spec on the next and subsequent changes. Axles are a bit different, being more difficult to change you should use a quality fluid on the first change as long as no leaks are present.

Always look for bluing, or any discoloration, chipped gear teeth, grey sludge, and grit lines.

 

[Honky Kong jr]

Only because you are shifty and too cheap to buy real B&M fluid.

Cheap or smart...... lol does the same thing and I’ll keep the extra cash for beer.

 

[Frankenchevy]

To the guys with th400, did you “shim” the filter tight with washers? I’ve read a lot of trans builders and off road guys will do this rather than leave the factory slop in the filter...

 

[Honky Kong jr]

To the guys with th400, did you “shim” the filter tight with washers? I’ve read a lot of trans builders and off road guys will do this rather than leave the factory slop in the filter...

Mines tight and has a deep pan with the filter extension.

 

[Frankenchevy]

Mines tight and has a real pan with the filter extension.

What brand or was that an oem option?

 

[Honky Kong jr]

What brand or was that an oem option?

I have Th400s from 1 tons they have factory deep pans. There is a but though. To run the 1 ton 400 you need a “special” slip yoke as they have a fixed home. On my V10 I had a spacer made because the output shaft is the wrong length. It can be switched out for the right length shaft but I didn’t feel like it. Lol also I meant deep pan not real pan stupid phone.

 

[Frankenchevy]

Can you tell what my setup is based on these photos? I could slide under the truck to take better ones when it’s not raining. The depth of the pan is about 3-1/4”.

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[74 Shortbed]

Looks like a TH400 with a truck pan.

 

[Frankenchevy]

Looks like a TH400 with a truck pan.

But just a standard depth..not a deep pan?

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[74 Shortbed]

They are deep compared to passenger car units..

 

[Frankenchevy]

Not sure why it attached the image again, sorry