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80/90 weight in the transmission?

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Luke_Healey

Luke_Healey

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Tonight I finally got around to cutting the carpet on the tunnel of my 'new' 66 Sprite to get access to the rubber plug that lets me get at the transmission fill plug. To my surprise, there was gear oil in there.

I drained it out and refilled the transmission with 20w50 motor oil. Hopefully there is less than 10,000 miles on this arrangement, and the transmission looks like it was entirely replaced, or rebuilt completely when they put the car together in 1989.

The car shifts fine and all the synchros work fine. It's quiet in all gears. There would be no situation where the transmission would require 80w90 after a rebuild??
 
When I had my gearbox rebuilt they recommended synthetic 90 rather than 20/50.

I might see a guy this weekend who rebuilds boxes (Silverstone Classic), if I do I'll ask him.
 
MG always said to use engine oil in the gearbox (that I know of - haven't read any other recommendation made by the factory)....remember, these are not the huge US transmissions.....20w50 is fine.
 
What would be nice is a magnetic drain plug so I could keep an eye on wear to the steel parts. I guess I'm more concerned about wear to the brass parts.

My other Sprite has apparently had the right oil in it its whole life, but grinds when shifting into 2nd or 3rd, so I have to double clutch it into those gears to smoothly engage.
 
The viscosity of the gear oil is determined during the design process. Some newer AGMA standards refer to the pitch line velocity, and may recommend thicker oil for their gearboxes. But the MOWOG gearbox was designed using the BGA standards. The factory recommended viscosity is necessary to allow the correct oil film between contacting teeth. Don't try to re-engineer something that gear engineers spent a long time designing. In worst case, thicker oil may shear and prevent good lubrication of the surfaces, therefore surface pitting.
 
Yeah, I'm running what's originally supposed to be in there. I was just curious if for any reason you'd be running 80w90 gear oil after a rebuild or something.

I will get under both of my sprites to make sure they're running at least the same transmission case. Do the 1500 Midget transmissions look different?
 
Since we're running 20w/50 in our gearboxes, what would be the effect if you dropped in some of the Lucas oil treatment? Would you use the one for engines, transmissions, or not use it at all? I've got 20w/50 in mine, but considered putting Lucas in mine to smooth it and quiet it down a bit, especially 1st gear.
 
I drive mine on the interstate every day and found that there is a heat build up with the 20W50 after about an hour. I found that stright 30 weight non detergent with eight ounces of the Lucas stabilizer has given me the smoothest shift and the least heat on the long drive. Before this combination I ran 20W50 castrol synthetic and then the Synthetic blend. Which in both cases cause hard shift problems after the heat build up. I have been running the 30 weight Lucas combination for over a year now with no issues. That would be about twenty five thousand miles.

Anthony
 
jhorton3 said:
but considered putting Lucas in mine to smooth it and quiet it down a bit, especially 1st gear.
Click to expand...

Remember, 1st gear in any Spridget tranny other than the 1500 boxes is a straight cut gear, and is inherently noisy.
Jeff
 
I dunno Anthony. You've only tried that combo for 25,000 miles... report back when you hit 100,000. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
 
So which Lucas stabilizer did you use, the one for engine oil or one for transmissions?
 
""""""""What would be nice is a magnetic drain plug so I could keep an eye on wear to the steel parts. """""""""

Always a good idea. Search for "wondermagnet"......I have no idea if he is still in biz.....Colorado I think. Use the 1/4" x 3/4" magnets for drain plugs. He has Neobedmium (SP??) magnets for real cheap. Drill a 1/4" hole in the plug and epoxy a magnet in.


"""""""""""""" The factory recommended viscosity is necessary to allow the correct oil film between contacting teeth""""""""

The material of the blockers and synchro rings have a lot to do with the type of lube required.


"""""""""""""I drive mine on the interstate every day and found that there is a heat build up with the 20W50 after about an hour. """"""""

Two things..... you should be using straight 40W or 50W. Best case is an ILSAC rated oil or better yet Redline 40 or 50W withthe BLUE label and NOT the RED label. However , using a synthetic, it will find more places to leak....especially the fiber washers on the bottom of the trans case. I would suggest NO additives. Second thing.....the input and output shaft shims (clearances) could be too tight. Clearances decrease with heat. With only 1.3 quarts of lube that trans get really really hot running at 3- 4k rpm.


"""""""""""I will get under both of my sprites to make sure they're running at least the same transmission case. Do the 1500 Midget transmissions look different? """"""""

They should both be the Sprite trans (ribcase or smooth case) the Stanpart trans (1500) is way physically diferent and was never in a Sprite...just the 1500 Midget. Look in your Moss or VB catalog for pix/line drawings.
 
I used the Lucas stabilizer for the engine. By the way if you have Dollar General store in your area they carry the Lucas for seven dollars a bottle that the local parts stores sell for thirteen. Although the first gear is stright cut the lucas still quiets it down a bit. It also enabled me to downshift when below five MPH without grinding. Trevor, I hope to put that many miles on it. The odometer tripped back over to zero and now has another 14K on it in the last five months.

Anthony
 
My personal preference, but I don't like all those additives...
 
This whole time I'd been seeing Lucas and thinking it was a UK product, but now I know what you're talking about.

I bought some Lucas transmission fix stuff and finally decided not to use it in my F150 after seeing that demonstration about it making oil foam up on one of those oil guy websites.

Instead I use it in an oil can to lubricate rusted metal stuff /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
 
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