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What oil to run in my ZF gearbox?

G Guest
I've spent hours reading everything I can find about what oil is best for the ZF gearbox.

I read the GL5 oils are bad for the "yellow metals" in the transaxle, and I've been told there are no "yellow" metals in the ZF, unless rebuilt with cheap parts.

The box was rebuilt by a reputable builder, I know this, with an extra tall 5th gear installed so freeway cruising is not buzzing the engine. I forget the name of the company but it's 3 letters like RBT or something.

I want to run the best oil I can get for my new ZF box.

I've been told "any good 90 weight is fine", I've read about people running the Castrol Hypoy C GL5 that one of the reputable builders here recomends. I found that but it was like $33 a quart (maybe a misprint?).

I've read about people using all the different Red Line offerings, "Shock Proof Medium", "Shock Proof Heavy", and Red Line "MTL".

I found Brad Penn who makes an 80-90 GL4 non-synthetic, that is probably first in the running, my local shop can get it in a day or 2.

I know I might be opening a can of worms here, because the more I read, the more different answers I get.

I'm OK with switching to synthetic, but I've read if you use too slippery of an oil, the synchros don't grab enough, and don't slow the gears down between shifts and cause shifting issues.

SO, my first inclination is to run a non-synthetic GL4 formula oil, probably the Brad Penn (I know Brad Penn is good stuff).

If the GL5 thing doesn't matter, I'd love to run Swepco oil in my gearbox, but it's GL5, so I'm hesitant until I get solid advice or information/proof that running GL5 has no negative effects. I know Swepco is REALLY good stuff, from my Porshe racing days.

I've asked 10 different people and gotten 10 different answers, so I know if I run Brad Penn 80-90 GL4 non-synthetic, I should be fine, but I'd like to hear what others have to say.

My ZF gearbox is very dear to my heart now, and I want to run the best oil I can run in it.

IF, there's no issue with GL5, is there any advantage to running the Red Line Shock Proof heavy or medium? The "Shock Proof" part sounds like it might be a good thing to run, if that's what it does. I don't plan on beating on this box very hard, so again, probably any 90 weight would be fine, but I'd like to hear what others think about the subject.

Thanks for any help or advice,

Mike
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jfb05177jfb05177Member
quote:
Originally posted by mike the snake:
...The box was rebuilt by a reputable builder, I know this, with an extra tall 5th gear installed so freeway cruising is not buzzing the engine...


DO you know what 5th gear ratio was installed? Do you think they also changed 4th to even out the shifting rpm droop?
and finally, what rpm are you running at 70MPH?

As for which lube, I'll just wait till Ron tells me what he put back in mine Smiler
George PGeorge PAdmin.

The gearbox lubricant needs to satisfy the requirements of a limited slip differential, the "spiral-bevel" ring and pinion gears, bearings of all types, transmission gears and the synchronizer rings. The lubricant must also be non-corrosive to the metals used to manufacture the various parts within the gearbox.

ZF's original recommended gearbox lubricants had viscosity ratings of SAE 80 or SAE 80W90, and an API GL-4 rating. Castrol 80W90 Hypoy Gear Oil (rated GL-4) was among the lubricants ZF originally recommended to Ford. GL-4 lubricants are medium load lubricants in which the additive package has been specifically formulated to meet the requirements of limited slip differentials and synchronizer rings, while being non-corrosive to aluminum and yellow metals. API GL-4 lubricants are common lubricants for transmissions and transaxles.

Some guys have good luck with synthetic oils, others find the synthetics tend to leak (drip) from all the seams between castings and from the seals, in those cases the owners have returned to petroleum based oils, and the leaks stopped leaking.

Last edited by George P
lf-tp2511lf-tp2511Member
quote:
hypoid ring and pinion gear sets (such as the gear set within the ZF 5DS-25

I have come, after doing oil research some months ago, to believe the Pantera ZF is NOT a hypoid ring and pinion style.

All I know is what I read.

Can anyone add some clarity to this?


Cutaway of our ZF - note the pinion and ring gear centers are on the same plane, not offset:

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George PGeorge PAdmin.



Larry, nothing personal. Honest. Forgive me just the same. My concern is that I'm already behind on forum clean-up.

This topic should remain focused on the lubrication needs of the ZF, i.e. the OP's original question.

A new topic in regards to Larry's point may be educational for all of us. It seems Lloyd could answer this question quickly.

Last edited by George P
lf-tp2511lf-tp2511Member
Nothing personal George, but the topic of hypoid versus spiral bevel is not a thread hijack when discussing the needed gear oil in our ZF transaxles.

The forces found in an offset (hypoid) R&P are greater than those in a spiral gear R&P, and thus the two styles have different lubrication requirements.

I'm posting the RBT FAQ Andy refers to.

I only know what I read.

Larry

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davidnunndavidnunnMember
George,

It seems that new Pantera owners (and some of us long-time owners) are looking for specific gear lube recommendations, as opposed to reading debates on whether to use GL-4 vs. GL-5 and to a lesser degree synthetic vs. mineral based gear lube. As far as the synthetic vs. mineral based oils are concerned, Lloyd Butfoy says synthetic based oils are fine to use but the ZF might leak a bit when using them. Lloyd told me, even brand new or freshly rebuilt RBT's (ZF's) can leak a bit when using synthetic oil. In these cases, some will stop leaking after a period of time, when the gaskets "swell up". The only real benefit to synthetic oil, in a street driven Pantera, is the ZF may shift a bit better.

Oddly enough, the specs in our owner's manual calls for GL-5; however, I have always believed that to be a misprint or a typo. I'll take RBT's recommendation over DeTomaso's without hesitation!

As mentioned in previous postings, it's vital that the oil is changed in a ZF once per year. The reason for this is, condensation tends to form inside the ZF's case.

Here are a few gear oil recommendations. All of these oils are safe to use in our transaxles:

Redline MT-90. This is a synthetic, GL-4 gear oil, 75W90.

Redline 75W90-NS. This is a synthetic GL-5 gear oil but without the friction modifiers for hypoid gears, common to GL-5 gear oils.

Brad Penn (formerly Kendall) Classic. This gear oil is a mineral based GL-4, 80W90.

I hope this helps.
R 1Rocketship (Guest)
Just a thought...If given time when using synthetic gear oil, the gaskets will "Swell Up", would pre-soaking the gaskets in the synthetic gear oil help eliminate the initial leaks/ing ?.

On aside note, I would Definitely use the gear oil recommended by a ZF transmission specialist like RBT, as patently obvious their experience & expertise is unmatched in the industry...Mark
R 1Rocketship (Guest)
quote:
Originally posted by mike the snake:
I inquired and Roger did the gearbox himself, using parts and seals and the tall 5th gear from RBT.

The box is butter smooth right now, but I have no way of knowing if Roger used brass synchros or bushings, so I'm going to stick with a GL4 oil.
Hello Mike; I would suggest with a great deal of confidence, that if you spoke with RBT & referenced Roger's name along with the serial number of your ZF, that chances are very likely that RBT has the invoice & parts list of Rodger's order that would determine what type of syncros were ordered/installed.
MT mike the snake (Guest)
Ahhh, GREAT idea!

Thanks for the tip.

The group of Pantera people I'm meeting and talking with are all he nicest, most helpful bunch of people.

I appreciate the tips.

Thanks again.

Mike



quote:
Originally posted by 1Rocketship:
quote:
Originally posted by mike the snake:
I inquired and Roger did the gearbox himself, using parts and seals and the tall 5th gear from RBT.

The box is butter smooth right now, but I have no way of knowing if Roger used brass synchros or bushings, so I'm going to stick with a GL4 oil.
Hello Mike; I would suggest with a great deal of confidence, that if you spoke with RBT & referenced Roger's name along with the serial number of your ZF, that chances are very likely that RBT has the invoice & parts list of Rodger's order that would determine what type of syncros were ordered/installed.
O osofastMember
Hi Mike I haven't welcome you to the forum yet so welcome to our addiction.
I am a big fan of synthetic lubricants and a very big fan of Redline products. I love how they work and what they can do. It is amazing how well this oil works, from reducing gear mesh noises, to ease of shifting when this oil is used. Also from how "thick" the HeavyShok is you will not experience any leaks that others have reported from the ZF with other brands of synthetic oils.
I would recommend that you change the oil in the ZF yearly to.
Jeff

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panteradougpanteradougMember
quote:
Originally posted by 1Rocketship:
quote:
As soon as I put it in, the shifter felt tight and new.


"As soon as I put it in, the shifter felt tight and new".



HEY Doug!!!...You are talking about the ZF transmission right??!! Yeah Baby!...Mark


Yes. Hall recommended I try this stuff 20 years ago. Maybe 15, before I tore the ZF apart.

It had the effect of tightening the feel of the shift mechanism and certainly quieted the second gear grind to not being there.

Even if it doesn't work for you and you have to change the synchros, at least it is worth the shot at about $50 vs. the cost of new gears, synchros and whatever else.

I think it might have a particular component of a friction additive that even though it is synthetic and therefore slipperier than dinosaur remains, the synchros seem to like it?

I'm thinking that maybe the original formula of lube was miss prescribed, or maybe just that's all there was back then? I don't question it. Just a suggestion to those who are changing their trannie lube now.

Do whatever you feel appropriate. I'm not making any money on any of this stuff. I have no dog in the hunt.
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