T10-M1 best gear oil 90W

[6s1640]

Hi all,

I am refilling the BW T10-M1 with new gear oil.  The owner's manual says 3.5 pints and to use 90W, mild to extreme pressure-M568-D. When filling, I was only able to get 3 pints in.  So just for grins, I check with the internet on best way to fill and what I learned was to only use GL-4 80W-90 gear oil.  It turns out I put in GL-5 80W-90. The info I am getting and confirmed with the NAPA guy, the GL-5 is corrosive on the brass synchro's and should not be used on our older transmissions.  I have drained it out.  Ugh.  Now I am looking for the correct GL-4 80W-90 gear oil, but none of the retailers stock, so I am having to go mail order or special order.

Do you have a recommended brand, old school gear oil 90W?  I want to stay away from synthetic and used regular gear oil, just like back in the day.

Thanks

Cory

[CSX4781]

Hi all,

I am refilling the BW T10-M1 with new gear oil.  The owner's manual says 3.5 pints and to use 90W, mild to extreme pressure-M568-D. When filling, I was only able to get 3 pints in.  So just for grins, I check with the internet on best way to fill and what I learned was to only use GL-4 80W-90 gear oil.  It turns out I put in GL-5 80W-90. The info I am getting and confirmed with the NAPA guy, the GL-5 is corrosive on the brass synchro's and should not be used on our older transmissions.  I have drained it out.  Ugh.  Now I am looking for the correct GL-4 80W-90 gear oil, but none of the retailers stock, so I am having to go mail order or special order.

Do you have a recommended brand, old school gear oil 90W?  I want to stay away from synthetic and used regular gear oil, just like back in the day.

Thanks

Cory

Cory,
  Redline makes some good products. I have a wide ratio toploader on my exSCCA 67 Mustang sedan racer use their gear oil in it, works well. You might give it a looksee.

Dave

[6T6/7]

Another option is PennGrade.

[6T6/7]

To add, Redline is synthetic. PennGrade is conventional.

[s2ms]

Hi Cory,

I ran Redline MT90, 75W-90, GL-4, for years but would occasionally pop out of 2nd gear under hard deceleration, just figured it was because the original gear was worn and that's the way it was. Then tried Redline 75W90 NS, which is GL-5 but advertised as synchro safe and recommended for "Muscle Car applications like Ford Top Loader, Muncie transmissions, Borg-Warner T-10 and Super T-10", but had the same problem. Then tried PennGrade 80W-90,GL-4 conventional and so far it hasn't popped out of 2nd, very smooth shifts.

Dave

[Road Reptile]

Hi Cory,
Should be easy to find-try the nearest Ford dealership.Just bought some for a rear axle and it was in stock.Hope this helps.
R.R.

[brandosaac]

All of the Toploader / T10 rebuilders ive spoken with stress to use GL-4
and NO GL-5 , NO synthetics that can wear out your brass

[68stangcjfb]

From David Kee's Toploader website about lubrication. T 10 should be similar. https://www.davidkeetoploaders.com/specifications.htm

 OILING SPECIFICATIONS

BREAK IN

Fill your Toploader with any quality 80W-90 GL-4 gear lubricant until the oil level reaches the fill plug opening. It should take approx. 2 quarts. We recommend changing the gear lube for the first time between 500 and 1000 miles to remove the grease used to pack the needle bearings that has dissolved, Permatex, break in metal, glass beads etc. We use several new parts in our transmissions and they will seat in with each other during the break in period. It is not uncommon to see very fine metal on the magnetic drain plug when you drain the oil the first time.

MAINTENANCE

We recommend changing the gear lube every 20-25,000 miles in normal street driving applications. If you have higher than stock horsepower or drive your car aggressively you should change the gear lube every 10-15,000 miles. We recommend Brad Penn 80W-90 GL-4 gear oil.

ROAD RACE TRANSMISSIONS

Toploaders used in racing applications need a break in period. Put some EASY laps on the transmission at low to mid rpm lightly accelerating and decelerating in each gear. This will give the gears a chance to break in and dissolve the grease in the needle bearings used during assembly. After a few laps, drain the transmission and clean the magnetic drain plug, then fill with 2 quarts of high quality GL-4 gear lubricant. Once completed, the transmission should be race ready. We recommend Brad Penn 80W-90 GL-4 gear oil.

SYNTHETIC GEAR LUBE

Synthetic oil is very popular in the automotive industry today. The way a Toploader is designed it needs a certain amount of friction for the blocker rings to synchronize shifts. We have had people try synthetics and say it works great and some say it doesn't work at all. Everyone agrees that standard gear lubricant does work. The biggest determining factor as to whether it will work or not is the driver. If you drive your car normally and shift it normally synthetic would be a great choice. If you drive aggressively or want to shift fast then synthetic may not work well. If you try synthetic gear lube and it does not work for your driving style drain the transmission and try standard 80W-90 GL-4 gear lubricant.

GL-5 GEAR LUBE

GL-5 gear lubricant should not be used in a 4 speed Toploader due to the extreme pressure additives that are aggressive to the soft metals.

[6s1640]

Hi All,

Thank you for your input.  It has been very helpful and educational.  I hope others will benefit too from your input.

Take care

Cory