QuestionQUESTION: I just purchased a 1980 Spitfire that has sat for 3 years. I just got the engine running and now I want to change the remailing fluids but don't yet have a manual, these are on order. Can these fluids be easily changed and replaced with the car on jack stands> Where are the drain and filler plugs located? Can I use an 75 / 90 synthetic gear lube in both units. I will also change the brake and clutch slave fluids.
ANSWER: Hi Jim,
Unfortunately, BLM in their infinite wisdom decided not to put a drain plug in many of the differentials so first just remove a couple of the lower bolts holding the 3rd member to the rear housing and if it does not have a drilled through hole, you will have to loosen all of the bolts or get a suction pump and remove it through the side filler / level plug.
The gearbox has a drain plug in the bottom and a filler / level plug on the side.
As far as synthetic gear oil, I have no experience with them and since you can't ware gear oil out, you can only contaminate it. So I ask why bother with synthetic oil. The factory recommended 80/90 hypoid gear oil.
Howard
---------- FOLLOW-UP ----------
QUESTION: Thanks very much for responding....Yes, this is why I didn't see anything that looks like a drain plug on the Differential. I'm not sure what you mean by 3rd member to rear housing? Is this a differential cover similar to covers on american made differentials? Will there be a gasket replacement needed?
The interest in synthetic is I have used this for many years on all my 60's muscle car 4 speeds and differentials. in addition to consistant viscosity over a wide range of temperatures the coffeficient of friction is lower than normal lubricants so less drag.
Again thank you.
AnswerHi Jim,
By 3rd member, I mean what domestic mechanics call the "chunk". There is a danger of braking a gasket but if you are going to use synthetic, I think you should clean it out as I don't think the two are a good mix.
It may be better as far as friction fighting, it is just that I quit working on these cars in a dealerships before any synthetics were available so I had no experience with them. If you are sure they work in a transmission, that may be true but I do know from experience that you can't get the trans too friction free or the syncros will not operate at all. We had customers bring their MGs and Triumphs in to us when they put STP in their trans. and found the syncros quit working and they got a lot of gear clash on every shift. The fine edges of the syncros could not brake through the surface of the STP to gain enough friction to get the gear and the hub assembly at the same speed so as to not cause gear clash (spline clash)
Let me know if it works ok so others will know. I am building a 215 Olds V-8 for a MG V-8 conversion and plan to use synthetic oil in the engine only since I can build it from scratch with synthetic oil.
let us know,
Howard
