Tranny and LS Diff Fluid replacement

[nils_h]

I am planning to change the manual transmission fluid and rear LS differential fluid on my 74 GTV 2000.

I was planning on using Redline synthetic products in each, but have been told that I will have major leakage if I do. I don't know what type of fluid is currently in either. Is there any way to tell what's in there now?

BTW, I use synthetic Castrol oil in the crankcase...the PO used synthetic in crankcase too.

Also, I purchased a pump to remove and refill the tranny and rear axle. Any gotchas I should watch out for?

[aussie74GTV]

I use Agip Rotra MP (80W90) for both my tranny and my LSD and I haven't had any problems. Don't know about the Redline stuff cos I haven't seen it down here.

I don't think there are any gotchas. While you're under there though you'll propbably want to check the condition of your rubber donut and rubber driveshaft supports. If you find any tears (not just cracks) you'll need to replace the part.

[Roadtrip]

Transmission gotchas/suggestions:

1. Remove the FILLER plug before you remove the drain plug. Use the correct size wrench and don't round off the edges. If you bugger up the filler plug, you're going to have to add the exact amount of fluid through the shift tower since the filler plug hole sets the correct quantity. A buggered filler plug will likely have to have the transmission out of the car to repair.

2. Drain and refill while the car is LEVEL. If it's not, you'll likely overfill it.

3. Fill it with a long tube from the engine compartment, or use a pump.

4. Transmission oils: DO NOT use "EP" rated gear oil in the transmission. The syncros are lousy enough as it is and EP oil will just make it worse. Besides, the additives in EP oil may cause accelerated wear on the gears.

a. Alfa's recommendation: Shell SPIRAX 90W HD

b. Synthetic recommendation: Redline 75x90 NS (make sure it's "NS") If the gearbox is old and prone to leakage, the synthetics won't help that situation. If you're getting seepage now with non-synthetic, I probably would shift to it now. I've heard some people say Redline helps weak syncros. I heard some people have had very good success with Redline MTL (Manual Trans Lubricant) helping weak syncros as well. Maybe someone else on the board can confirm or deny that.

c. For worn boxes with weakening syncros, PAPAJAM recommends just straight 50W motor oil (NOT multigrade). I've never tried that, but it sounds interesting. I guess the straight 50W motor oil is about the same viscosity as 90W gear oil, but maybe a little stickier.

Differential gotchas/suggestions:

1. If you've got seepage out of the pinon seal, this would be a good time to fix that.

2. Oil: Alfa recommendation: Shell SPIRAX 80/90W, but just about any GL-5 hypoid gear oil should work fine.

3. While you’re down there, grab your pinion flange and give it a good yank and see if you have any play. You shouldn’t. I would remove the bottom plate to drain the oil completely and inspect whatever is visible.

When you replace the drain plugs, I would recommend that you use anti-seize compound to make removal easier in the future.

[ar1750gtv]

Has anyone used Spirax S (synthetic) in their gearbox and/or differential?

I wonder if there is much difference between this and Redline synthetic gear oils?

Are there any compelling reasons to not use synthetic gear oil?

Thanks for your input.

Shell Spirax S

[Naplesworkshops]

The only experience that I have in this matter is that I did switch to Redline MTL in my '74 GTV to try to resolve a baulky shifting problem when cold. The first to second gearchange was very difficult for the first five or ten minutes of driving in cooler weather and so I thought that a switch to synthetic may alleviate the problem.

With MTL I was in fact able to change up and down immediately even in the coldest weather and I felt that all the gearchanges were somewhat smoother. I did not experience any additional leakage due to the use of the synthetic lube.

Thanks