Need help on rear axle fluid change on 41 Sedanette.

[Eddie-O]

Hello folks,

This might sound like a dumb question, but I need some advise on changing my rear end fluid. The manual leaves a lot to be desired and I want to be sure I'm doing this right.

Do I drain the fluid at the rear cover and refill through the cover plug? Or, do I drain from the bottom plug in front of the axle behind the torque tube and refill on the top plug? I plan on cleaning out the housing and gears and replace with 85-90 W hypoid oil (do you all agree?) and refill. Is the correct level when the oil is just below the hole on the rear cover plug or else where?

Thanks for your help in advance. 

Ed

[Ben Bruce aka First Born]

Drain from bottom cover bolt hole.  Don't touch that one on the torque tube.  Refill through the rear cover plug and full is at the level of the plug.

 

  Ben

[Matt Harwood]

My preferred oil is this:

 

 

Available at NAPA or O'Reilly's. GL4 is what you want for a '41. The thicker viscosity will be beneficial since you don't run it in cold weather. We have all experimented with various types and viscosities, but there seems to be a general consensus that this stuff is the right stuff for big Buicks of this vintage. I've been running it in both the transmission and rear end of my Limited for three or four years and it not only shifts better, but it's quieter and cooler. I'm pleased with it.

 

Here's a link to my trials and tribulations when I decided to simply change the rear end fluid in my Limited. It turned into a major ordeal that included some custom made parts, but now that it's back together I still recommend this Sta-Lube oil. You can safely ignore the part where I installed the rear end cover with the wrong orientation and over-filled the differential and the part where I let others goad me into taking everything else apart until I dropped something important and broke it. My advice? Drain it and fill it, leave the rest alone.

 

 

Edited April 2, 2020 by Matt Harwood (see edit history)

[Eddie-O]

Thanks Ben and Matt. I'll drain from the cover bolts and fill to the plug level. Since this is my first pre war I'm curious about the unit on the end of the torgue tube in front of rear housing. It has what appears to be a drain plug on the bottom and a fill plug on top. Should I service this also and if so, use the same gear oil? I know it's a stupid question, but what is it and what's it's purpose?  Have never worked on a rear axle with this unit on it and I can't find anything in the manual about this unit. It shows the axle assy. but not that unit! The manual is very vague. Is there a better manual  like Chiltons or Motors for a 41 available? Did a search, but no luck on the 41.

Sorry for the nieve questions, but I am very new to pre war.

Thank's again guys

Ed

[southpaw]

Ed,

I think you may have an overdrive unit installed. We need pictures!

Jim

[Matt Harwood]

Go to the link below and download the 1942 Buick shop manual, which is widely regarded as the most complete manual for our cars. Yes, I know yours is a '41 and this is for '42, but the cars are mechanically identical and the '42 manual really has a lot more than the '41. Note that to make this download work, you can't just hit the DOWNLOAD button, you have to hit each individual category, open each page file, right click on the page and select "Save as..." and download each page separately. It's tedious and will take you a half-hour or so, but that's the only way to get it. I reference mine almost daily.

 

Here's the link: http://oldcarblog.com/manuals/1942/Buick shop manual/index.html

 

Hope this helps!

[Eddie-O]

South paw, I'll post some pics tomorrow. It has me stumped since I've done more than one rear axle overhaul through the years and have never seen this. Like I said earlier, there is a fill and drain plug on the unit so I'm sure it needs to be serviced at times with fresh fluids which I'm going to guess would be gear oil. But since I'm in doubt, I want to be sure. I'll have pics ASAP tomorrow.

Thank's

Ed

[Matt Harwood]

Does it look like this?

 

Or like this?

 

Those are overdrive units installed in torque tubes.

 

 

Edited April 2, 2020 by Matt Harwood (see edit history)

[Ben Bruce aka First Born]

I THINK he is talking about the pinon bearing lock sleeve  lock screw and nut. NO SERVICE NEEDED.

 

  Ben

[neil morse]

Matt, I don't want to hijack Eddie's thread, but thanks for that tip about the '42 manual.  I hadn't heard about that.

 

Neil

[Eddie-O]

Matt,

Yes, it is similar to those pictured. Like I said, I'll post some pics tomorrow and hopefully get this resolved and what to do for servicing it.  I don't know when anything was done to it before since I just got the car last Friday.  Been going through the whole car and doing all fluid changes and am almost ready to do a decent road trip ( shake down cruise ) as soon as I work this out. I did look at the 42 manual, but nothing I could find in there either. 

I'm not  talking about pinion lock sleeve and nut! I'm familiar with those and have done many rear axles in 25 years with Chevrolet. Just never pre war cars.

To be continued with pics.

Thank's to all

Ed

Edited April 3, 2020 by Eddie-O (see edit history)

[Eddie-O]

Matt,

Would that 140 gear lube be a bit to thick for a Sedanette both in the axle & trans? Just curious since I'm going to go with that brand but was concerned that since it would be driven at limited distances ( under 100 miles ) at a time it might make a hard shift situation?

[Matt Harwood]

Vehicle size and distance don't matter. The thicker oil will slow the gears down when you come to a stop, making it easier to shift into 1st. I used 85W90 at first and it was always a fight to drop it into gear at a red light. The 140 cured it. Since you will not be using it in cold weather, the thicker oil will work just fine.

[neil morse]

I second what Matt says.  I'm using the 140 weight on his recommendation, and my transmission seems very happy.  Shifting is smooth and quiet.