Rear Differential Access on Chevy Based Roadtrek

[ManWonder]

I thought I'd do a little maintenance on my 2004 Chevy-based Roadtrek 190P. I had in mind to replace the fluid in the rear differential. But when I looked under the van I saw that the generator was very close to the differential - maybe too close. Does anyone know if one needs to remove the generator to gain access to the differential?

[booster]

Originally Posted by ManWonder

I thought I'd do a little maintenance on my 2004 Chevy-based Roadtrek 190P. I had in mind to replace the fluid in the rear differential. But when I looked under the van I saw that the generator was very close to the differential - maybe too close. Does anyone know if one needs to remove the generator to gain access to the differential?

I am assuming you have the non towing package rear axle? Might be similar for the larger towing pkg axle, but even tighter.


There is no drain the housing so you either have to remove the cover or suck the oil out with a suction gun. Both are messy and tough with genny right there, but doable. If the fill plug has never been out, in may be very, very, stuck and hard to get out, even to the point of needing to get the cover off to put heat on it. Refill needs to be done with suction gun or pump. Anyway you look at it, it is an ugly job.

[Stevemo]

There are 4 nuts to remove in order to drag the generator back out of the way.

https://www.youtube.com/watch?v=d6ZsgJkWISI

Checking the fluid level when you are done is the hardest part.

https://www.youtube.com/watch?v=fcDu2GONDUo

[ManWonder]

thanks for all the helpful info especially on the genny removal which in my case would likely mean i would not put it back in

[tomnorman457]

If you remove your Onan 2800? I’m looking to buy one if it’s running right, and it’s one of the more recent versions. (Spec K)

[cruising7388]

Originally Posted by booster

There is no drain the housing so you either have to remove the cover or suck the oil out with a suction gun. Both are messy and tough with genny right there, but doable. If the fill plug has never been out, in may be very, very, stuck and hard to get out, even to the point of needing to get the cover off to put heat on it. Refill needs to be done with suction gun or pump. Anyway you look at it, it is an ugly job.

Is this also the case for the 60S differential in current production?

[booster]

Originally Posted by cruising7388

Is this also the case for the 60S differential in current production?

Yes, the 60s and 70s have the same style cover. The only difference for here is that the 70s stick back about 3/4" further toward the genny than the 60s. This is assuming they are still using the 60s and haven't gone to the similar American Axle axles on current production.

[cruising7388]

Originally Posted by booster

Yes, the 60s and 70s have the same style cover. The only difference for here is that the 70s stick back about 3/4" further toward the genny than the 60s. This is assuming they are still using the 60s and haven't gone to the similar American Axle axles on current production.

Whose idea was it to turn a brief and simple operation into a lengthy tedious messy job?

IIRC, the 70 full floater has dry axle tubes but the 60/60S semi floater has flooded axle tubes to lubricate the rear wheel bearings. Without a low drain point, how is this fluid recovered and how are the axle housings recharged?

[SteveJ]

I'm gonna have to investigate exactly what rear end is installed on my y2k 200 RT. It has a drain which I didn't discover until I was re-installing the rear cover. The genny was in a different location on this unit, so no interference with removing the cover.

I wonder if the cut away chassis or the antiqueness of it explains the drain on it.

[booster]

Originally Posted by cruising7388

Whose idea was it to turn a brief and simple operation into a lengthy tedious messy job?

IIRC, the 70 full floater has dry axle tubes but the 60/60S semi floater has flooded axle tubes to lubricate the rear wheel bearings. Without a low drain point, how is this fluid recovered and how are the axle housings recharged?

The 60s is a semi-floater with the axles supporting the wheel weight and single outboard wheel bearings.


The 70s is a full floater that has no weight on the axles and uses two wheel bearings in a hub similar to front wheel bearings.


Both of the axles lube the wheel bearings with differential oil so would have wet axle tubes. The 60s drains straight back after getting oil by splash, and the 70s wheel bearing hubs get fed by splash but also have small capacity to hold some oil.



Of interest is that the 60s uses a roller bearing for wheel bearings that does not have an inside race. The rollers run right on the axle, so if you eat a bearing is will normally also take out the axle. Side load is carried all the way back to differentlal and pickup off axle clips inside the carrier bearings. The 70s uses two very large tapered roller bearings in each hub which pick up the weight and side load. The axles have only torque on them and carry no weight or side load.


Interesting about the earlier model on a cutaway having a drain. That is one generation older than the other Chevies post 2003 which might be it, but also it is cutaway which is normally sold into heavier service so that could be it also. I added a drain to our differential case and to floating hubs to make oil changes much easier. I can fill ours though the floating hubs so don't have to fill though the cover plug. I do remove the plug, though to know when I am full.

[peteco]

Originally Posted by booster

I added a drain to our differential case and to floating hubs to make oil changes much easier. I can fill ours though the floating hubs so don't have to fill though the cover plug. I do remove the plug, though to know when I am full.

How did you add a drain to the case.

[booster]

Originally Posted by peteco

How did you add a drain to the case.

I had good access because I had it mostly apart during the axle swap, but it can be done in place easily also.



I just chose a place that was low in the housing so would drain the most oil, and that had enough wall thickness to drill and tap a pipe plug into.


I used a small 1/8"npt plug to keep good thread length, others have used 1/4", though, at least on the 60s. I think the 70s actually had a thinner casting wall than the 60s. May be cast steel instead of cast iron. It is a good idea to have the cover off when you do it so can be certain to get all the chips out.


I did similar in the floating hubs with 1/8"npt plugs.


Of interest is that the 70s full floaters hold oil in hubs so they always get lube even before the splash get there on starting out. This does a couple of other not so good things, though. First is that you don't get all the oil out of the hubs when you change the differential oil, maybe 1/2-1 pint or so may be left, and if you replace a hub seal or bearing, when you put it back together there is no oil in it for a while which is a bad thing with new, dry bearings.


There are a couple of ways to address it all. I put in the drains which takes care of both issues as I get all the oil out, and I fill back into the hubs so they are full of new oil immediately. For hubs with no drains, the truck guys and shops will usually put a light coating of wheel bearing grease on the bearings when installing them to get through the initial fill delay. Many will also either jack up on side of the vehicle as high as they can get it safely to let the diffy oil gravity into the hub, then do the same on the other side. Parking side hill in a steep ditch also works, I have been told.

[dicktill]

Originally Posted by peteco

How did you add a drain to the case.

Originally Posted by booster

<snip>
I used a small 1/8"npt plug to keep good thread length, others have used 1/4", though, at least on the 60s. I think the 70s actually had a thinner casting wall than the 60s. May be cast steel instead of cast iron. It is a good idea to have the cover off when you do it so can be certain to get all the chips out.
<snip>

Pete,

My 09/10 C190P Roadtrek (still) has the Dana 60 rear axle. I was able to drill and tap for a 1/4" NPT drain with the rear axle "in-situ". Not overly difficult with the rear cover removed, but then I had the Onan out too, so YMMV. I used a lot of paper towels and a magnet to remove the chips inside, which weren't that many as most of them will fall down as you are drilling from below. I think that I stuffed the housing with a bunch of paper towels when I was drilling/tapping. I also flushed the casing out a bit with some oil with the drain plug still removed, and then re-wiped with more paper towels (the drain hole is not at the very lowest point). Having the Onan in place should only affect cleaning out the chips, not the drilling and tapping. Of course, if you have an add-on rear sway bar as I do, it has to be removed. I can take and post a picture of it if you wish.

Manwonder,

In answer to your original question, you should be able to remove the rear cover to drain the fluid with the Onan in place, although it is a bit more difficult to do. The cover does not use a gasket, so you must meticulously clean both it and the rear axle before reassembling. Here (per Booster) is the special goop to use when replacing the cover:

Right Stuff is a black special RTV that originally came in a cheese whiz type aerosol can and was claimed to be OK for auto trans pans without a gaskets. Most RTV won't handle ATF, but it did seem to work good. They still make it that way, but also have in tubes under another name like Ultra Black or Super Black. The stuff is really strong and sticky so can help hold the cover in place while you get the screws is somewhat. Pretty sure it is Permatex/Loctite brand.

One final note to all,

I had a lot of difficulty "chiseling" the cover off, because of the goop that attached it, and because the cover is only 0.060-0.080" thick, and has no "lead-ins/chamfers" to help you get a chisel under the edge. Therefore I did a bit of damage to both the cover and the housing, which I fixed with a bit of filing. Then I chamfered the inner (forward) edge of the cover on both left and right sides, so the job would be easier the next time. Perhaps I needed a chisel that was shallower/more tapered, more like a wood chisel (I think I actually used some sort of gasket scraper).

Regards, Dick

[peteco]

I have used a Mityvac oil extractor to suck out the differential fluid on my 2006 RT 210P Dana 60 (I assume). I did this at 55,000 miles and 110,000 miles. After the initial oil extraction from the differential plug opening, I raise one side a few inches to let the oil in the axle drain into the differential. Then I raise the other side for that side to drain. Only a very little amount of oil seems to drain into the differential, so I don't know that raising each side is that important. I do try to bend and force the extraction tube to the bottom of the differential but don't know for sure that I get it there.

My question for booster, dicktill, or others that have had the cover off: do you think that using an extractor has a high likelihood of leaving a lot of oil in the differential, and that I should remove the cover for a complete drain and/or install a low drain plug?

[booster]

Originally Posted by peteco

I have used a Mityvac oil extractor to suck out the differential fluid on my 2006 RT 210P Dana 60 (I assume). I did this at 55,000 miles and 110,000 miles. After the initial oil extraction from the differential plug opening, I raise one side a few inches to let the oil in the axle drain into the differential. Then I raise the other side for that side to drain. Only a very little amount of oil seems to drain into the differential, so I don't know that raising each side is that important. I do try to bend and force the extraction tube to the bottom of the differential but don't know for sure that I get it there.

My question for booster, dicktill, or others that have had the cover off: do you think that using an extractor has a high likelihood of leaving a lot of oil in the differential, and that I should remove the cover for a complete drain and/or install a low drain plug?

I think that "lot" is a highly variable term to different folks


There is often a low spot that is right under the ring gear in many differentlals, but I don't recall on the 60s or 70s for certain. That area would be blocked if it is there, does a cup of oil not out make much difference, probably not, but you would see the new oil darken quicker.



Not too surprised on a 60s that you would not get much out by tilting, as the bearing butts up against the axle seal in the tube so no reservoir that I know of. They sling oil up into the tube fast enough so it gets to the bearings, I think, and then it all drains back to the diffy. They normally would not like to keep oil laying on the axle seal when sitting, as if it leaks it get into the brake area many times.


Many people tend to run the diffy oil a bit high on both the 60s and 70s it appears from what I have read. They claim lower wheel bearing temps if the oil is just above the axle tubes in the diffy. I could see this at cold start, but at highway speed much of the oil would be being slung around so the level would still be below the tubes, but who knows for sure.

[Stevemo]

You can see in part of my video where I scoop out a fair bit from the bottom of the 70S so you would want to keep sucking until you get 1 US gallon as that is what I put back in.
I hope the 70S really is a full floater, the GT4 axle code did not reveal much useful information or even a proper cover gasket when I researched it.

[booster]

Originally Posted by Stevemo

You can see in part of my video where I scoop out a fair bit from the bottom of the 70S so you would want to keep sucking until you get 1 US gallon as that is what I put back in.
I hope the 70S really is a full floater, the GT4 axle code did not reveal much useful information or even a proper cover gasket when I researched it.

Very easy to tell if you have a full floater.



Just look at the wheel with no hubcap or cover on it. If the hub center is nearly flush, it is a semi floater. If the hub sticks out past the wheel center and has mounting bolt heads on the end of it, it is a full floater.


If you really want to get all the oil out for a change, you will need to put drain/fill holes in the hubs as there is no other way to get the oil out without removing them.

[Luv2Go]

Originally Posted by dicktill

Pete,

My 09/10 C190P Roadtrek (still) has the Dana 60 rear axle. ....

Regards, Dick

Dick, do you happen to remember how many quarts of gear oil you needed to fill your Dana 60S, and what type/brand you bought? I'm working on mine soon and it would be nice to know before-hand.

[dicktill]

Originally Posted by Luv2Go

Dick, do you happen to remember how many quarts of gear oil you needed to fill your Dana 60S, and what type/brand you bought? I'm working on mine soon and it would be nice to know before-hand.

I am pretty sure that it took almost 3 quarts (I bought 4 and have an unused one left over). The expen$ive oil I used was Red Line full synthetic 75W90NS, on the recommendation of ... drum roll ... who else but ... Booster.

[Luv2Go]

Originally Posted by dicktill

I am pretty sure that it took almost 3 quarts (I bought 4 and have an unused one left over). The expen$ive oil I used was Red Line full synthetic 75W90NS, on the recommendation of ... drum roll ... who else but ... Booster.

Thanks!

For some reason on mine 3 quarts filled to 1/4" below the hole, good according to the GM manual but I bought another quart of Red Line anyway to top it off. With the issues I have with this axle I don't want it running low.