I have been using Valvoline Synthetic Blend Gear Oil SAE 80W-90 in the gear box for about 6 years.
Valvoline.com > Products > Grease Gear Oil > Gear Oil > DuraBlend® Synthetic Blend Gear Oil

I have also been using Mobil 1 Synthetic Gear Lube LS 75W-90 for the differential.
Mobil 1 Synthetic Gear Lube LS 75W-90

 

Gary, thanks for the response.
Looking at the specifications for those two oils I noticed that the Mobil specifically states that it is intended for use with 'yellow metals'-ie brass synchro rings-but the Valvolene does not--that would concern me given that the ZF box fitted in the Montreal uses brass synchro rings.

 

Interesting, I checked all over the net and the general thought is...

"Lubes which meet MT-1, will not attack yellow metal even if the temperature does climb to this extremely high 250 degree mark."

Valvoline says it's gear oil is, “Recommended for (conventional and limited slip) manual transmissions where an API GL-5 or MT-1 fluid is specified.” So maybe I'm safe?

There is a lot of interesting information on the web site called, “Bob is the Oil Guy”. Bob Is The Oil Guy - Forums powered by UBB.threads™

 

Link

Dear members,

Have a look at the following link:
http://www.alfabb.com/bb/forums/164-168-1991-1995/163727-manual-transmission-gear-box-oil-2.html

Ciao, Olaf

 

Dear members,

Have a look at the following link:
http://www.alfabb.com/bb/forums/164-168-1991-1995/163727-manual-transmission-gear-box-oil-2.html

Ciao, Olaf

Hi Olaf, I am not sure how you cunningly slipped that in while I wasn't looking!
Lots of opinions---I have sent a request into ZF to ask for their recommendation.

 

Hi Gary, yes that "Bob is the oil guy" thread is interesting alright. The problem as always is sorting fact out from uninformed opinion, and there is a LOT of that on the 'net of course.
ZF recommends the Pennzoil/GM "Synchromesh" for their new manual transmissions but that doesn't mean it would be OK for the older designs. Does anybody know if the transmission in the Montreal-the ZF S5-18/3-uses Porsche style synchromesh. Many later transmissions use Borg Warner style synchros which have different lubrication requirements and operate best on ATF type fluids I have learned that earlier Porsche style synchros require thicker oil and more friction to operate properly.

 

The Zahnradfabrik Friedrichshafen AG (ZF) published assembly, maintenance and operating instructions manual for the S 5-18/3 gearbox states the following on type of lubricant;
1. mild EP gearbox oil preferably SAE 80
2. HD engine oils SAE 30

Does anybody know if the transmission in the Montreal-the ZF S5-18/3-uses Porsche style synchromesh.

From the parts breakdown pics, the syncros are Borg-Warner.

 

From the The Alfa Romeo Montreal Website:

Alfa Romeo recommended changing the gearbox oil at intervals of 18,000 km. Both the fill plug on the right side of the box and the drain plug at the bottom require a 19 mm socket. Alfa initially recommended the use of a monograde SAE 30 engine oil such as Shell Rotella T30. In December 1972 approval was given to Shell Rotella SX30. The viscosity of these oils is 10.9 cSt at 100 deg C, which corresponds to ISO viscosity grade 100, on the border between gear oil viscosity 80W and 85W. Shell Rotella oils are no longer sold in some countries and Shell Aseol (Switzerland) recommend the use of Shell Rimula X30 as a substitute. For proper synchromesh operation, it is probably unwise to use synthetic oils or any kind of friction-reducing additive in the gearbox. However, Philip Hehir uses Redline Blue Schockproof oil in the gearbox of his racing Montreal. The gearbox drain plug is fitted with a magnet which should be cleaned with each oil change.

 

I use Redline products in the transmission and diff. Been using them in the Montreal since '97.

 

This from the Reline Oil website:

"GEAR AND SYNCHRONIZER WEAR PROTECTION
Most manufacturers of manual transmissions and transaxles recommend an 80W or 90W GL-4 lubricant. GL-5 gears oils which are required in hypoid differentials are not used in most synchromesh transmissions because the chemicals used to provide the extreme pressure protection can be corrosive to synchronizers, which are commonly made of brass or bronze. Typically, the use of a GL-5 lubricant in a synchromesh transmission will shorten the synchronizer life by one half. The extreme pressure requirements of spur gears and helical gears found in transmissions are not nearly as great as found in rear-wheel drive differentials. A GL-4 lubricant provides adequate protection for most manual transmissions, unless a unique design consideration requires the extra protection of a GL-5."

So unless your transmission fluid is also lubricating the differential you don't want or need GL-5 is how I read the above.

 

I just received this response from ZF:

"David,

Thank you for contacting ZF Service North America in regards to the S 5-18/3 transmission. I was able to locate a paper copy of the assembly, maintenance and operating instructions. I have included the first several pages including technical data, description, maintenance and lubrication. As an automotive enthusiast I appreciate the need to keep up with modern technologies and all the advances in fuel, lubrication and tires to just name a few to keep are our older vehicles operating safely and provide the service life we expect.



Under the maintenance and lubrication section you will find a reference to EP gear box oils with a military spec, preferably SAE 80 or HD engine oil SAE 30. I am not an expert in lubrication but do recall the new Synchromesh fluids to be a lower viscosity. Due to the need for better fuel economy many manual fluids moved to 5w30 motor oil or Dexron. These fluids if used may cause leaks or difficulty with the clutching action of the Synchro’s. You may want to contact someone in the lubrication field to compare specs on some of the new fluids but I feel using any fluid that meets the MIL-L-2105 spec should provide sufficient protection. Due to the removal of Zinc from modern motor oils I am not sure if use of SAE 30 will have an effect on wear properties within the transmission.


As for the comparison of the Synchro’s to Porsche I would need the identification numbers from the ID plate located on your transmission. If the S 5-18/3 was also used on Porsche I should be able to locate an application and compare parts. As far as I’m aware all synchronizers work the same way while some newer versions may use composite coatings or powdered metal in place of brass. I have only viewed the catalog pictures on the S 5-18/3 and could not identify their composition.


Hope this helps,


Best Regards,

Steve


Best Regards / Mit freundlichen Grüßen

Steve Jaffe

Regional Service Manager

ZF Automotive Technology Group



ZF Services North America , LLC

777 Hickory Hill Drive

Vernon Hills, IL 60061

Phone 847-478-6784

Steven.Jaffe@ZF.com "

 

Montreal gearbox specifications

Hello David,

I checked the book "Montreal, the essential companion" written by Bruce Taylor. He states that the gearbox is a Synchroma S 5-18/3 of which several versions were built. The Montreal gearbox type has reference: 1255 003 019 and this number should be quoted when ordering spare parts from ZF. This might help for the contacts with ZF.
The S 5-18/3 was, again accoording to the book, also fitted to the Alfa 6 and to the early versions of the Maserati Biturbo, launched in 1981. The assembly, maintenance and operating instructions manuals have a reference number: 1255 751 101.
The indications on gearbox oils have already been mentioned.

Ciao, Olaf

 

Thanks Olaf. I have copies of the official workshop manual but it was published in 1972 and there has been a lot of research and develpment done with oils since then-hence my question: Is Pennzoil/GM Synchromesh or other similar oil a good lubricant for these transmissions?
I will try asking Pennzoil I think.

 

I would do so too



Hello David,

Yes, asking Pennzoil would be the best thing to do. You could also ask the Dutch register leader of the Montreal Register/Alfa Romeo Owners Club (SCARB). Here is his name and address:

Will Mertens
Oud Boshoven 10
6002 NW Weert
The Netherlands
Telephone: +31495 536453
E-mail: montreal@alfaclub.nl

Ciao, Olaf

 

Hello,
As we discovered recently, The Syncros from my 1974 Alfa Montreal are Steel. I believe the earlier Gearboxes had Brass Syncro Rings. There are no signs of wear but after the rebuild, I would like to know what the best oil is. My Gearbox has a sign in the side "blue" plate that says the recommended oil from ZF is a 90 Grade.

 

Hi

Like many others I use redline products in the transmission and diff. Oils have come a long way in 50 years, so going off manuals that refer to grade and oils in existence back then won't necessary provide you the best solution for today. I find the redline products to be very good from cold and have no shifting or slow synco issues.

Regards Phil

 

Hi all,

I am not a Montreal owner, but I drive an Alfa 1750 GTV (105 series from 1970) since 2003 and a Fiat Dino 2400 since 2016.
As I am working as automotive engineer in engine and transmission development for more than 25 years, I am of course interested to feed my classics with the best possible oil.

The Montreal has more or less a similar ZF S 5-18/3 transmission as the Fiat Dino 2400. I just finished a complete gearbox overhaul at ZF classic in Germany and asked them for the recommended oil.

Their top recommendation is "Castrol Syntrans B75W". The ZF gearbox has Borg Warner synchros either in brass or in steel, both need high quality GL3 or GL4 which is not "slippery", any GL5 oil would cause severe shiftability and wear issues.

"nehmen Sie das Castrol Syntrans B75W freigegeben nach ZF TE-ML 11.
Die auf dem Datenblatt aufgeführten moderneren ZF Getriebe haben wie Ihr S5-18 Synchronringe und Gleitsteine aus den selben Werkstoffen.
Mit freundlichen Grüßen/Kind regards
Rüdiger Nitzschke
Leiter Technik ZF Tradition ( VTR )
ZF Friedrichshafen AG
88038 Friedrichshafen, Deutschland/Germany
Telefon/Phone:
+49 7541 77-2236, Telefax/Fax +49 7541 77-902236
e-mail: ruediger.nitzschke@zf.com

If you prefer Redline products, best choice is MTL .
IMPORTANT: Redline 75W90 NS GL5 is completely wrong for the Montreal ZF transmission, this oil is most likely the best recommendation for Alfa 105 transmissions with Molybdenium coated Porsche Synchronizers (and also for e.g. Fiat Dino 2000 transmissions), but much too "slippery" and chemically aggressive for BW synchros.

YvesMontreal has the same opinion and explains it very well in this thread:
What is it with this GL-5 gear oil??

 

The ZF Gearbox in a Montreal has a small plate on the side of the Gearbox Housing which calls for a 90 grade oil. I am currently using this in the ZF Gearbox which has recently been rebuilt by Larry Dickman Jr. It works perfectly, shifting even when cold. The best it’s ever been in the 35 + years I have owned it!

 

For your information, the Gearbox had never been rebuilt. It’s a 1974 model. All that was required was a Bearing on the Countershaft, we changed both. In my car the synchros are steel. The clearances were checked and assembled. I have posted the Thread on AlfaBB Montreal

 

I should have been more specific on the type of Redline oil. I use Red Line Light Shockproof Gear Oil (Blue) and my experience is with it in my race Montreal and from experience from other racers also using ZF transmissions (still using syncros and not straight cut) e.g. Ford Escort rally cars and the popular circle track stockcars here in NZ. This oil works great with the syncos in my transmission shifting smoothing and quickly (watch some on track footage as I'm don't believe I'm a slouch when shifting gears) when cold to when super hot at the end of a 12 lap race (I don't run a transmission cooler). As such I'd have no issue recommending this to a production car even though Redline provides the caveat (on all of it's race products) that it doesn't recommend for production cars. But I don't believe anyone is driving their Montreal in a "production car" manner e.g. a daily driver with all round weather conditions and doing high millage to be of concern.

Oil seems to be a topic that polarizes people with ones preference over another that can be so subjective based on build tolerances and materials, usage (or lack of) or the manner used/driven. There seems to be a topic regularly on oil in the Alfa BB so not surprised it can be confusing to get a consensus given both the breadth of oil products and peoples experiences.

Cheers
Phil.