Red Line MTL is the best bar none.

https://www.penngrade.com/penngrade-1/gear-lubricants/


I had to get special oil for my Super T-10. It's green in color.....it's out in the shop & I'll get info later.


Some of the new oils cannot be used in "classics".

Multi-Purpose ‘Classic’ Gear Oil GL-4 SAE 80W-90 (7729), 85W-140 (7735)

 
•Used with “yellow” metallurgy (brass, bronze, copper) and other ‘soft’ metals used in synchronizers, bushings, thrust washers and other components typically found in classic manual transmissions and transaxles

 
•Best for traditional manual transmissions, Muncie, Rockwell, NVG/New Process, Borg-Warner, Saginaw and Ford and many imports, including Nissan UD trucks, Mitsubishi Fuso trucks, Volvo trucks, and Mercedes Benz truck manual transmissions,  transmissions/transaxles on Nissan cars and SUVs, Mitsubishi vehicles and Suzuki vehicles calling for a GL-4 level lubricant

Ok dick so use atf in the trans?


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Ok checking the rear end and I do not see any drain or fill plugs


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The only thing the manual says it's a German trans


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The fill plug is probably on the driver's side of the third member.

There is no drain plug. You have to pull the third member to drain the fluid, which is BS in my opinion. If your trans is the stock 4-spd, then it's probably the same way: a fill plug and no drain.

Sta-Lube is my go-to for GL-4 gear oil for use in older transmissions. Redline MT-90 is also GL-4, but I would only use it for very long drain intervals or hard driving.

Thanks
Please excuse my inexperienced but what is the third member




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A couple of things to bring this together:

1. You car doesn't have a T-5 unless it was a 5 speed swap. Even if it did there were some early T-5's that used gear oil, or an after the fact recommendation of a gear oil/ATF mixture. So, ATF in a T-5 is not a complete given.

2.  Since you state it is a German trans we can assume it is a factory 4 speed. It more than likely specs GL-4 as the gear oil. Be watchful because GL-5 is often what you find and they hint (the old "meets or exceeds") that it is OK to use because it exceeds GL-4. However, there are a lot of warnings out there that something in the GL-5 eats the brass syncro's in the trans.  So, go with GL-4 only (specifically) in the trans. You just have to find it.

3. I'm not exactly sure why the center section of the rear end (where the gears are) is called the third member.  Perhaps because the axles count as one & two??? The term is also more commonly used on the rear end that you have (Ford 8") because that front section is removable as a unit with the gears.  It is what you see in the first picture in post #7. The lesser Pinto rear end, the 6-3/4," has the center section and the axle tubes as one unit and the gears have to be fitted into it. It has a simpler stamped steel cover for access.

4. Yes, a lot of cars have no drain plug, you have to pull covers and let it flow.  Some people drill a hole, weld on a nut and use a gasketed bolt to help the "next time" they need to do the task. I do it to my Auto Trans pans and it does make the process nicer.

 Without the drain plug on the 8" rear end you have to loosen the whole third member and run the risk of damaging the gasket. Which becomes a pain to replace because you then have to drop the drive shaft, pull the brake backing plates and slide out the axles. On the 6-3/4" it is easier because the cover simply slides off.  So, keep that in mind if you opt to change the fluid in your 8". If you find the fill plug you might consider removing the fluid by suction (though thick as it is...).

The rear end has no brass in it so so you can use GL-4 or GL-5 in it.

I'm not up on OEM Pinto diffs..... that looks like it may be a 9" ?

If so, it may have a traction lock ?
If so, it will also need friction modifier.

Thanks

Not sure what' rear is in there it was like this when I bought it. It's a 1980 cruzing  wagon


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It's a 8" rear end. The 8" flattens on the top and bottom where as a 9" is round. See for yourself .

Poor guy is really getting confused with T-5 lubrication recommendation s and 9" speculations.  As far as has been mentioned he has a stock 1980 Cruise Wagon with the factory 4 speed (he mentioned German trans) and an 8" rear end (visible by the pictures in post #7). Use GL-4 for the transmission and either GL-4 or GL-5 for the rear end.  Also see below about the mentioned additive IF you have traction lock.

The easiest way to know if you have a traction lock (sometimes call "limited slip") system is to safely jack up both rear wheels. Turn one wheel. If they both turn in the same direction you have traction lock. If the opposing wheel turns in the reverse direction you have what is referred to as an "open" rear end. Should you find you have a traction lock system (I doubt it, but you never know) you need to investigate what is the proper additive. I have no experience to make an additive recommendation . But it was a good point made to consider when replacing fluids in the rear end.

I want to thank everyone for  all the assistance


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For clarification to the original poster and to avoid further confusion the "Third Member" is also known by "The Center Section", "The Carrier", "The Pumpkin" and sometimes just "The Rear End."