sail2fast

After five years of storage I revived my '94 C4 with a full tune and some other fixes. Runs like a top.

Since we have a 914 around as well, I had plenty of Swepco dino tranny fluid (the 914 leaks tranny fluid and we have to keep it stocked). So I put it in the C4...

Result: cold shifting was _very_ notchy. Difficult even. Only somewhat better when warmed up.

I looked up what the last shop to change tranny fluid used (Kendall NS-MP), so I just changed back to Kendall.

Result: silky smooth shifting, even when cold.

I know there are lots of threads on this, but I'm just giving a plug for the Kendall

P-daddy

Bought my car with Swepco by PO. It was somewhat notchy in cold weather (<40F). I thought maybe the fluid was getting old and a trans fluid change would fix that. Wrong! I drained and filled with fresh Swepco and the result was the same...crunchy shifts! This winter I will try Mobil Delvac. Thanks for sharing your experience with Kendall.

Rocket Rob

Glad a simple switch of fluid solved your problem. I'm running Swepco in both of my cars and its been working well for me.

jody stowitts

Heard that the synthetics (mobil1, et. al.) work better with these Bendix type synchros, as opposed to all the pre-1988(?) transmissions (915 types $ earlier?).

sml

from my research ... 2 options ...

1. Mobil Delvac 75W90, or

2. Or the premium defence/military oil ....
Lubrication Engineers Synolec 9919 75W-90 ...
I live in the wrong country and this stuff was about US$150 per litre!

and just remember what GT Gears advised ....
"Delvac is a Mobil, not a Mobil 1 product. I've had customers go buy Mobil1 gear lube thinking it was Delvac. The primary difference is the Mobil1 has LSD friction modifiers in it and Delvac does not."

FeralComprehension

FWIW, I use the proper Redline product (75w90?) with a shot of Heavy Shockproof in it. It's never notchy, but seems a little slow to spin up. No problem if I double clutch.

sml

'proper' .... ?

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If you track your car do NOT use the Redline. It's got the same slippery issue that Geoffery was talking about with the Mobil1 LS. When the Redline gets really hot at the track it gets too slick and they synchros don't work right.

You constantly see guys posting about how the Redline cured their balky shifting issues in 1st and 2nd when the car is cold or in the winter. That's because it's more slippery. That same slickness that's an advantage for the street guys becomes a liability at higher temps. on the track.

Regards,

Matt Monson
Guard Transmission LLC

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That's correct. I disagree with Redline and what they would recommend you put in your gearbox. I've just seen too many gearboxes in race cars go bad when using their products in a racing application. Like I said, it's a decent street oil and a lot of people like it. In my business, my bias is racing. When I give input and advice on gearbox care it's going to be influenced by what we see at the track.

For a street car that sees weekend track use as a DE vehicle we recommend Mobil1 Delvac or Porsche's factory fill, which these days is made by Shell. They are both reasonably priced and relatively easy to source, at least here in the states they are.

While both of the above oils would also be satisfactory for track use, what we recommend for dedicated racecars is Lubrication Engineers. A number of the Grand Am and PCA teams that we work with have used that oil with great success in their vehicles. They have seen an average of nearly 20 degrees lower gearbox temperatures over the length of a race, which for a PCA enduro is a 1 hour+ and for Grand Am can be 3-6 hours in duration. Heat is what kills these sorts of parts and if it runs cooler it's gonna last longer. However it's probably overkill for a street car, especially since you've got to buy it in 5 gallon pails.

But you know what the best thing about free advice is? One is free to ignore it. It won't hurt my feelings if you choose to use Redline in your car.

Regards,

Matt Monson
Guard Transmission LLC

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Brant,
I think that I may need to further clarify my earlier statements that were quoted above. The complaints that have come to me from customers who have used Redline in their synchronized race gearboxes had to do with shifting quality. In short, their complaints had to do with synchronizer issues.

I say this because I have NEVER seen any evidence to suggest that Redline gear oil is a danger to your gearsets themselves, and in fact the feedback that the pro teams are giving me is that their sequential gearsets seem to be wearing better with Redline than when they used Delvac.

I mention this because I don't want you to be at all concerned that you are hurting your gearbox by using this oil. In fact, your personal experience on two different gearboxes, one of which you have had apart, suggests quite the contrary. So please, don't be concerned.

We all know the old saying that Opinions are like A-holes and that we've all got one. That was the primary reason for me commenting in this thread at all. I am not the end all answer to the great gear oil debate and in fact I usually try to stay out of the fray because I think there's a bunch of good gear oils on the market.

In fact, I probably shouldn't have made such a generalized blanket statement above in the first place because I don't know the mileage on the gearboxes that had the issues I described. I don't know the customer's service interval on their gear oil. I don't know if they had OEM synchros in it, or one of the new aftermarket options. There's too many variables at play there for me really to have any business speaking so absolutely on the subject. I should have been a bit less dogmatic and said something to the effect of, "you should be aware that in some instances we've had race customers complain of shifting issues late in a race on a hot day when using that particular oil" or something to that effect.


Really, if it ain't broke don't fix it. You've had no problems with Redline NS up until now, so why change? There's really only a couple of hard and fast rules in my book with gear oil for Porsches:
1. GL5 rated. The ring and pinion is built into your gearbox. You've got to go GL5 because of that.

2. Change it often. For a racecar, every 2 or 3 race weekends. For a DE car with some street use in between, probably twice that interval is best.

3. If you have an LSD in the car do NOT use a gear oil with LSD friction modifiers. Friction modifiers are an NVH thing, not a performance thing. They make it more slick and the LSD doesn't lock as well. And in some instances, the friction modifiers may be guilty of some shifting issues because the synchros do in fact need friction to function.

If you follow those three simple rules, you'll do all right. Delvac, Redline, Motul, Royal Purple, Lubrication Engineers... They are all good oils. I don't recommend just one as best, which is why I so rarely even post to the gear oil debates that happen so frequently on this board.

Matt Monson
Guard Transmission LLC

FeralComprehension

Proper viscosity is all I meant.

My car is not a race car; I can buy redline locally and have used it for years in all my machinery without dissatisfaction provided I chose the right fluid for the car. I did once use the wrong weight fluid in a Miata 'box and the results were less than desirable.