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Hello all, I am finished with the cosmetics on my 70 and now want to change fluids and standard tune up.
I know asking the oil/fluid questions come with allot of personal opinions so just want to know I am on the right track with my decisions
Motor oil I am using Mobile 1 15w50 as I always do here in AZ.
4 speed transmission fluid I plan on ordering this
as for differential fluid I plan on this combination
I know opinions will be personal but is this all a good excepted products package.
I will research capacities, my 4 speed has a lower drain plug and I have a fluid pump for diff... when it comes to the diff, I will suck out as much as I can but when filling should I premix the fluid and additive to a specific ratio before filling... I read to add the additive first then the fluid but what about the unknown remaining fluid in the diff... will that not throw off the fluid/additive ratio or am I over thinking this.
I will also be ordering a set of plugs, coil, cap and points... its been a very long time since ive done a points tune up, will I want to get anything more.
Thanks in advance
Last edited by Golfobsessed; Oct 19, 2025 at 10:23 AM.
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No expert by any means but I use Mobil 1 15w-50. The other fluids look ok to me. Id add the bottles of posi fluid first to the rear diff. Yes, you will get many different opinions.
Thanks guys... just wanted to verify what im ordering for trans and diff are good options, doesn't appear to be a documented ratio of diff fluid to additive and I read as many people suggesting 1 4oz bottle as 2 bottles of additive... perhaps I will go in the middle
I think your fluid brand choices are good ones. Nothing skimpy about either Driven or Lucas. I've used both in my cars and not had any problems.
I used 2 small bottles of GM posi-additive and don't think it matters much the sequence of when you put it in compared to the base lubricant -- it's all going to get mixed up very quickly when the diff turns. That said, I squirted about 1/2 bottle of lube into the diff, poured the additive into the bottle, shook it up and emptied the rest of the bottle into the diff. I don't recall how much base lube it takes, but think you're going to open a second bottle to top off.
Originally Posted by kansas123
Is there anything in the world that smells as bad as differential gear oil? Yuck, you'd think it was something biological rather then geo.... wow
How do you feel about grape-flavored? The GM diff lube has a quite pleasant grapey smell, as if that really matters in life...
I think your fluid brand choices are good ones. Nothing skimpy about either Driven or Lucas. I've used both in my cars and not had any problems.
I used 2 small bottles of GM posi-additive and don't think it matters much the sequence of when you put it in compared to the base lubricant -- it's all going to get mixed up very quickly when the diff turns. That said, I squirted about 1/2 bottle of lube into the diff, poured the additive into the bottle, shook it up and emptied the rest of the bottle into the diff. I don't recall how much base lube it takes, but think you're going to open a second bottle to top off.
How do you feel about grape-flavored? The GM diff lube has a quite pleasant grapey smell, as if that really matters in life...
I think your fluid brand choices are good ones. Nothing skimpy about either Driven or Lucas. I've used both in my cars and not had any problems.
I used 2 small bottles of GM posi-additive and don't think it matters much the sequence of when you put it in compared to the base lubricant -- it's all going to get mixed up very quickly when the diff turns. That said, I squirted about 1/2 bottle of lube into the diff, poured the additive into the bottle, shook it up and emptied the rest of the bottle into the diff. I don't recall how much base lube it takes, but think you're going to open a second bottle to top off.
How do you feel about grape-flavored? The GM diff lube has a quite pleasant grapey smell, as if that really matters in life...
Thank you... perfect, I wasn't concerned about the sequence only ratio... didnt want to get two bottles of additive in and not enough room for diff fluid if I couldnt get all the old stuff out... I will see how much I can remove with the pump and judge from there.
Most of the unpleasant smelly stinky odor of heavy gear oil is due to Sulfur; no coincidence Sulfur's a big part of those "who did that?" pharts as well.
Fluid changes motor, trans and diff.
