Rear differential and 120% tranny flush

[xopher]

I needed an oil change, and I still don't have the gear/space to do the work myself, so I went to a decent full-service oil change place today for 6.5 quarts of 5W-20 Mobil 1, which she drinks pretty well every 3000 miles. They did the full inspection, commented on how worn the back tires were, and added that they didn't blame me one bit.
When they got to the rear differential fluid, they said it was pretty dark needs to be changed every 30k miles or so, and recommended synthetic 80W-90. I erred on the side of saftey/being scammed and told them to do it. I watched them put in 75W-90. How many miles should it be between changes? What should I be putting back there? They also put in some kind of performance additive (without charge). Does this sound right?
Last, they said the tranny fluid was getting dark and might need a change soon. He said they have a machine they hook up which "uses the old fluid to push the new fluid in" and results in a 120% flush. Whenever people start talking about percents greater than 100, I ask myself if they are making a joke/figure of speech, or if they are completely full of crap? Which was it in this case? What does a 120% flush mean?

[fastblackmerc]

I needed an oil change, and I still don't have the gear/space to do the work myself, so I went to a decent full-service oil change place today for 6.5 quarts of 5W-20 Mobil 1, which she drinks pretty well every 3000 miles. They did the full inspection, commented on how worn the back tires were, and added that they didn't blame me one bit.
When they got to the rear differential fluid, they said it was pretty dark needs to be changed every 30k miles or so, and recommended synthetic 80W-90. I erred on the side of saftey/being scammed and told them to do it. I watched them put in 75W-90. How many miles should it be between changes? What should I be putting back there? They also put in some kind of performance additive (without charge). Does this sound right?
Last, they said the tranny fluid was getting dark and might need a change soon. He said they have a machine they hook up which "uses the old fluid to push the new fluid in" and results in a 120% flush. Whenever people start talking about percents greater than 100, I ask myself if they are making a joke/figure of speech, or if they are completely full of crap? Which was it in this case? What does a 120% flush mean?

Engine oil capacity is 6.0 quarts (5.7 liters).

Differential fluid is usually dark. Factory spec is 80w-90, 75W-90 is OK. Most of us that have replaced the stock gears run 75W-140 full synthetic. The additive they put in was most likely friction modifier which you don't need if you go with a full synthetic oil.

Never heard of a 120% flush. Unless you replaced all the parts in the system - tranny, converter, lines and cooler you'd be hard pressed to get 100% of the fluid out. 30K intervals is good for fluid changes. It certainly can't hurt.

[RCSignals]

............He said they have a machine they hook up which "uses the old fluid to push the new fluid in" and results in a 120% flush. Whenever people start talking about percents greater than 100, I ask myself if they are making a joke/figure of speech, or if they are completely full of crap? Which was it in this case? What does a 120% flush mean?

He must mean "uses the new fluid to push the old fluid out", or draws the old fluid out drawing the new fluid in

What they are trying to do is push out the capacity of the transmission (100%) plus 20% over to try to get all the old fluid out. It's a bid of smoke and mirror talk.

[RF Overlord]

To answer your questions/concerns in order:

Diff fluid DOES get dark and that allows less scrupulous places to scare people into having it changed. You were probably fine, but there's no harm in changing it early. I do have 2 concerns, though. The first is with the "performance additive"...if it was actually friction modifier they installed, that's good as it's required with the Trak-Loc axle in the Marauder. If it was anything else, then your guess is as good as mine, but I wouldn't want some unknown miracle-in-a-can in my car. My second concern is that they installed 75W-90 when Ford now recommends 75W-140 synthetic in the Marauder. Those 2 factors would cause me to have it all changed out again, this time using the correct fluid and friction modifier.

Now on to the transmission. It sounds like they use a T-Tech or similar machine that does in fact use the transmission's own pump to push out the old fluid while simultaneously pushing in the new. As far as giving a "120% flush", they are probably used to dealing with average Joes who know nothing about cars and it's easier to say "120% flush" than it is to explain that the machine actually runs slightly more fluid than the transmission holds through it, so it has the effect of doing a complete exchange "and them some"...see? I can't even explain it a lot better. :rolleyes: Suffice it to say that it's legit, even if their description is dumbed down. BTW, here's (http://www.cloreautomotive.com/site_prod.asp?sku_pk=151) the link to the T-Tech site for a better explanation.

For change intervals, if you don't do any towing, then 50,000 miles for the differential is more than adequate. As for the transmission, doing a fluid exchange every 30,000 miles borders on the obsessive/compulsive. ;) :D

[RF Overlord]

The additive they put in was most likely friction modifier which you don't need if you go with a full synthetic oil.Actually, friction modifier is required in the MM regardless of the fluid installed. Some synthetic fluids already have the friction modifier in them (Royal Purple, for one) and therefor don't need any extra, but most do not have it, including Ford's own Motorcraft.

[fastblackmerc]

Actually, friction modifier is required in the MM regardless of the fluid installed. Some synthetic fluids already have the friction modifier in them (Royal Purple, for one) and therefor don't need any extra, but most do not have it, including Ford's own Motorcraft.

That is what I meant... I use Redline and it already has the friction modifier.

[larryo340]

For change intervals, if you don't do any towing, then 50,000 miles for the differential is more than adequate. As for the transmission, doing a fluid exchange every 30,000 miles borders on the obsessive/compulsive. ;) :D
Servicing the trans at 30K on these transmissions is good cheap insurance. Especially if you are driving it hard :burn:

I'm not sure what the manual says, but it used to be full drain and fill including torque converter 30K normal driving, and 21K in severe use.

Anybody know:
Does the stock torque converter in Marauders still have a drain??

[VAmarauder03]

I needed an oil change, and I still don't have the gear/space to do the work myself, so I went to a decent full-service oil change place today for 6.5 quarts of 5W-20 Mobil 1, which she drinks pretty well every 3000 miles. They did the full inspection, commented on how worn the back tires were, and added that they didn't blame me one bit.
When they got to the rear differential fluid, they said it was pretty dark needs to be changed every 30k miles or so, and recommended synthetic 80W-90. I erred on the side of saftey/being scammed and told them to do it. I watched them put in 75W-90. How many miles should it be between changes? What should I be putting back there? They also put in some kind of performance additive (without charge). Does this sound right?
Last, they said the tranny fluid was getting dark and might need a change soon. He said they have a machine they hook up which "uses the old fluid to push the new fluid in" and results in a 120% flush. Whenever people start talking about percents greater than 100, I ask myself if they are making a joke/figure of speech, or if they are completely full of crap? Which was it in this case? What does a 120% flush mean?

The Trans Flush Machine we use at work is hooked into a trans line somewhere and uses the line pressure of the old fluid to put in the new fluid, it however does not pump in more than what the trans holds, it only pumps in as much trans fluid as the amount that came out....

[GrazniM]

Servicing the trans at 30K on these transmissions is good cheap insurance. Especially if you are driving it hard :burn:

I'm not sure what the manual says, but it used to be full drain and fill including torque converter 30K normal driving, and 21K in severe use.

Anybody know:
Does the stock torque converter in Marauders still have a drain??



Nope - unfortunately they did away with that on the GM's & Vics back in 2001/2 or 3.... ixnay for Marauder also. To verify I popped the access plug and shimmed the converter one rev... no plug. :mad: ...so I put in a extra capacity pan and drop 3-4 quarts of tranny fluid with every or every other oil change, depending on my usage, to make up for it.

[larryo340]

Nope - unfortunately they did away with that on the GM's & Vics back in 2001/2 or 3.... ixnay for Marauder also. To verify I popped the access plug and shimmed the converter one rev... no plug. :mad: ...so I put in a extra capacity pan and drop 3-4 quarts of tranny fluid with every or every other oil change, depending on my usage, to make up for it.
That sucks, it is one thing I don't see why they removed it. I know a couple cents a car adds up but jeeeese.

When I service my trans after dropping the pan and draining the converter it takes 11.5 quarts of Mercon V to fill it up. I'm aware that some fluid is still in the lines, but I can live with that very small amount of old fluid mixed in.

[xopher]

...the "performance additive"...75W-90 when Ford now recommends 75W-140 synthetic in the Marauder...have it all changed out again, this time using the correct fluid and friction modifier.
Hopefully before the possible miracle-in-a-can or 75W-90 have a chance to do any real damage I can swap out for 4.10s and do it right.


Engine oil capacity is 6.0 quarts (5.7 liters).
Is that to halfway between the dots on the dipstick?


Servicing the trans at 30K on these transmissions is good cheap insurance. Especially if you are driving it hard :burn:
You can bet your a$$ I do.. :)

Thanks guys! I love a forum filled with people who contribute valuable information rather than arguing like slack-jawed mouth-breathers! You guys are the best!

[fastblackmerc]

Is that to halfway between the dots on the dipstick?


From the owners manual:

6. Wipe the indicator clean. Insert the indicator fully, then remove it again.
If the oil level is between the MIN and MAX marks, the oil level is acceptable. DO NOT ADD OIL.
If the oil level is below the MIN mark, add enough oil to raise the level within the MIN-MAX range.
Oil levels above the MAX mark may cause engine damage. Some oil must be removed from the engine by a service technician.
7. Put the indicator back in and ensure it is fully seated.

[xopher]

...MIN and MAX marks...
Do we know how much oil fills to Min and Max, respectively?