Transmission oil? Rear end oil?

[cdsmith]

Okay … The car went on its second road trip (another 1 tenth of a mile – no license or insurance, so the best I can do is a quick run up and down the street).

Now I’m thinking about changing transmission and rear end fluids. So here is the question: What kind of oil should be used in transmission and rear end? I've read that I should use motor oil (at least in the transmission), but nothing specific about what type, weight, whether or not it should be multi viscosity, and so on…

So… anyone out there willing to go out on a limb and make a definitive statement on this subject?

I do appreciate the help…
cd

 

[Tom Rynne]

20/50W motor oil in the tranny
90W gear lube in the differential

 

[spritenut]

I agree with Tom.
20/50 tranny
90 or 90/140 in the diff.
Stay away from synthetics in the tranny.
Something about synthetic oil that attacks the brass (or bronze) parts in the gearbox.

Frank

 

[cdsmith]

Thanks for the info....
cd

 

[sparkydave]

Depending on what year yours is, it may take SAE 90 oil for the transmission. The ones from '75-'79 did, but I'm pretty sure the Haynes book said all the spridgets took 90 weight in the trnasmission and differential.
-Dave

 

[77MidgetMkIV]

Sparky- so are you running the SAE 90 in your tranny? I am loking to do mine whilest it is on stilts for the brakes, and originally was going for the 20w50, but your comment on the 75-79 caught my eye, as I have a '77.

thx

 

[sparkydave]

Hi Mark, I've got SAE 90 gear oil in both the rear end and transmission. Supposedly the MGB calls for 20W-50 in its transmission, but my original owner's manual, the Haynes manual, and the MG Factory Workshop manual all call for SAE 90 in the Midget. BTW, if you need something to remove the fill and drain from the rear end, I made one from a 3/8" to 1/2" drive socket adapter. I just used a Dremel to grind the edges of the 1/2" end and it works nicely.
-Dave

 

[77MidgetMkIV]

Good to know! The wife is off on a girl's weekend this weekend, so I am stocking up everything for a couple days in the garage, so I will be picking up the oil today.
thx

 

[dklawson]

I've never heard of synthetics attacking anything in a gearbox. My understanding is that the additional friction protection normally attributed to synthetics makes them unsuitable for gearboxes as they reduce the effectiveness of the synchros (which must work by friction). Regardless, don't run synthetic in your gearbox.

Early Minis like mine share some gearbox parts with the rib case transmission Spridgets. Minis use 20W50 but we have to change it very frequently since they use the same oil for the gearbox, engine, AND the final-drive (differential) unit.

 

[77MidgetMkIV]

Yeah. I have gotten all the warnings on synthetic in the tranny, and if memory serves, there is a thread here somewhere regarding synchro functionality and synthetics.

 

[aeronca65t]

All 1500 cars run gear oil in the trans (typically 90 weight or so). This is the Spitfire/Marina all-syncro trans.

1275 and earlier cars (with the "ribcase" and "smoothcase" tansmissions) use motor oil (20W-50 works nicely).

As for sythetics, I do not use them in the engine but have had excellent results with Mobil 1 sythetic gear oil (and also Red Line gear oil) in the trans of my 1500 racer. When I switched from regular gear oil to sythetic, the trans shifted much faster and smoother. Every other Spridget I race with, also uses sythetics (they are all 1275 cars and use sythetic motor oil).
I'm using sythetic gear oil in the final drive also.....Sprite rears tend to be a bit more leaky than other cars, but the sythetic actually seems better in my car (hasn't lost a drop so far).
That's my experience anyway.

 

[Matthew E. Herd]

I'm just running generic hypoid gear oil in the diff and it leaks a bit (looks like I'll be rebuilding the rear axle soon, so I'll take care of that now). However, I definitely second Nial's comment about using synthetic gear oil. I replaced generic 75W90 hypoid oil which was blowing out of the trans with the Redline Synthetic offered by Moss. The stuff is wonderful! Shifts are faster and smoother, with generally a better feel. I also thought that I was losing trans oil, but discovered upon attempting to fill it that it was actually at the same level as it had been when I last filled it with Redline. I guess that means my rear main seal is leaking a bit ... hard to say. At any rate, using synthetic transmission oil in your 1500 is a good idea. I can't really speak for the older A series transmissions that take motor oil.

Matt

 

[77MidgetMkIV]

Well, this puts a new spin on it. I run synthetic in the engine, and it has been great. Aeronca and Matt- you have my interest perked on the synth. gear oil for my tranny. Are you of the opinion, then, that the cautionary tales regarding potential damage to the tranny's innards from synth. oil are off base?

 

[aeronca65t]

I'm basing my comments on my experience and I note that others I race with also seem to like syn-oils in tranmissions and final drives.
I'm not a chemist so I do not claim any technical analysis on the subject.
I am a mechanical engineer and I have noted no extreme tranmission wear (other than the normal wear-and-tear of racing).
Red Line has a bunch of tech-papers on line and they claim that their products do not void any warrantees. Here's a lnk:

https://www.redlineoil.com/tech.asp

 

[77MidgetMkIV]

Thanks for the input. At this point, I think I am leaning toward synth. gear oil. I also use Mobil 1 products, in my other vehicles and equipment, and am happy with it, so I will stay with that if I go this route.

 

[Matthew E. Herd]

Ditto about being a mechanical engineer ... except I'm just finishing my bachelors. /ubbthreads/images/graemlins/smile.gif Nial's done quite a bit more studying than I. All I can say is that moss recommends it and I think it works well in terms of shifting feel. If it's eating my synchros, at least it drives well at present! However, I'd bet that since it drives well, it probably isn't causing them to deteriorate. The same synthetic oil has been sitting in my transmission since last august and I've noticed no problems from the synchro standpoint (I had hydraulic issues, but they are unrelated).