AirtekHVAC

Soooo, what have we learned here??? Dexron III is good for our 5-spds? At least mine? (Hehe)...If so, sweet for me...I got a whole case of the stuff in me storage shed....I was going to get rid of it, but now....or should I go 75w90?

Hilton

I would be tempted to see what your shift quality/syncros are like with 75W90 before using Dex III.

I'd also choose based on your diff - if LSD I'd go with a 75W90 that has the correct additives for LSD. If open diff, I'd have no problem using Dex III per the WSM.

If you're not sure which you have, you can tell by having a look through the fill plug using a cheap ebay endoscope, or just take snaps with a digital camera in macro mode.

Take pics/look at 90-degree positions around the diff (i.e. rotate the rear wheels) - the massive holes and gears visible in the open diff cage are easy to spot.

85euro928

Ron,
after reading about fluids today more than anyone should have or want to I have two things to say: 1) make sure the DIII is the old type (thicker), and 2) I will be using Redline 75w90NS and adding the friction modifier 1oz at a time until my LSD no longer chatters.

hacker-pschorr

Funny how one of the top experts posts the perfect answer and yet everyone ignores him.

The Fixer

Ron,
See how your car shifts first,

i added it to mine only because i have slightly hard downshifts 4th to 3rd and 3rd to 2nd, otherwise i wouldn't use it because it's pretty thin.

It helped a great deal. I am still surprised how much it helped. Warm up time is much shorter. I only did half Dexron & 1/2 cheapo conventional 75/90 from Walmart as a test.

rgs944

That is why I asked about compatability about using this as an additive to quiet down my 2nd gear syncro but still keep most of the heavier oil in there.

The Fixer

Already well aware of this fact. It is a trans-axle.

But when you have tiring hard shifts and are faced with a rebuild anyway, why not give the DEXRON a go? There's nothing to lose.

Also Dexron was used in the rear axles of big American cars protecting them from wear just fine.

85euro928

Yup, it meant nothing to me the second time I read it too.

The Fixer

Probably going with Redline
Matt

Mike Simard

I just looked at some syncromesh I have and noticed it's thin. It's thinner than any other type of oil in my shop except WD40.
I bet it does improve shifting though!

Mike Simard

The original Dexron had whale oil which made it superior to anything available today. It's a superior lubricant and doesn't go bad requiring changing. It was a good idea to use that even in diffs, they kept LSDs happy and didn't need to be changed out.

There's no "equivalant" to that Dexron today.

Mike Simard

When the 928 was designed, Dexron had whale oil as I Discussed above. It was NOT Dexron III Porsche intended, I don't think III was even available until much later anyway but anything after the original Dexron is nowhere near the oil the original was.
Again, there is no equivalant to real Dexron available today and hasn't been since the 70s.

rjm65

Right, looks like Dexron II is what was around when the 928 was introduced, and that came out in 72 after they banned the use of whale oil in the original Dexron.

Mike Simard

I assume your manual says "Dexron" and not "Dexron II" or any other number.
They really should have stopped using the Dexron name completely after the ban, anything else is basically just bulk hydraulic oil with friction modifiers.

Just thinking out loud here but I contend that if Dexron (or any other whale oil lubes) weren't around in the 60s, limited slip diffs would have been designed differently to prevent complaints of creaking.

hacker-pschorr

If you had a 78-84 this would make a lot more sense. The 85+ transmission are not "known" for that so I would investigate the real problem before something gets worse.

With the early cars it's clear to me mis-adjustment of the double disc clutch combined with the Porsche style synchros is recipe for bad shifting.

You know as well as anyone around here, do a search and you will find thread after thread on the "horrible" notchy transmissions in the 16V cars, 2nd gear is difficult, they grind etc... along with endless chemical solutions to "fix" the problem.

Meanwhile I have over 100,000 miles on the original transmission in my 81 with over 400rwhp and it's smooth as silk. I'm also one of the most **** retentive owners when it comes to clutch adjustment (had it out 20 times i one day trying to source a slight hang up issue).

You know what they say about leading a horse to water.........