FLUIDS

[Joe C.]

My 1985 Corvette with 700R4 is starting to leak trans fluid from the pan gasket, whose bolts are tigtened firmly, but not overtight. The car has 33,000 miles, with the original trans fluid. I BELIEVE that the change interval is around 65,000 miles, with no TIME stipulation. Anyway, I will change fluid/screen/gasket. But have a few questions:

1. Is there a drain plug on the converter?
2. Recommendations for fluid. I use Castrol motor oil, so how about Castrol Dexron?
3. Is the generic Purolator screen/gasket kit as "good" as a GM kit?

I took Duke's advice, and filled my '65's crankcase with Rotella 15W-40 last fall. Should I do the same for the '85? Recommended oil for the '85 is 10W-30, and I have always used Castrol GTX 10W-30. I no longer drive the '85 much, maybe 500 miles/year.

Thanks in advance,
Joe

[Joe L.]

Re: FLUIDS

Joe----

1) There is no drain plug that I am aware of on any 700R4 converter. Consequently, a significant amount of the "old" fluid will remain in the transmission;

2) Castrol Dexron III will be just fine;

3) Personally, I wouldn't use the Rotella in the 1985 L-98. The Rotella, itself, would be fine. However, as you know, it's not available in the 10W-30 viscosity. I would recommend continuing to use the 10W-30 viscosity for your engine as GM also recommends;

4) Personally, I don't like Purolator products, alhough I'm sure that they will work just fine. If it were me, I'd use the GM kit even though it costs more. You can probably get one through Delco dealers for a price which is competitive with the Purolator. The filter kit you need is GM #8657926 and it currently GM lists for $39.35. I believe this kit contains the filter + all the gaskets you'll need;

5) Torque the pan boltsin a crossing pattern to the torque specified in your service manual. After 1,000 miles, or so, retorque to specifications.

[Jim T.]

Re: FLUIDS

No drain plug on the 85's converter. I used Texaco Dextron when I changed mine. Used the GM filter, don't know the better of the two between GM and Purolator. I changed my fluid at about 45K back in 1992 and will be going it again soon, it has 102K on it now. I use a inch pound torque wrench torque on the pan bolts. Noticed a little fluid on the pan few months ago and retorqued the pan bolts with my inch pound torque wrench. Looks like it stopped the seepage. Like driving the 85, the air conditioner is a great performer in hot weather.

[Duke W.]

Re: FLUIDS

I am hesitant to recommend CI-4 oils for cars equipped with catalysts. Modern oils for spark ignition engines don't have as "rich" an additive package as they did 20 years ago since some of these additive combustion byproducts are believed to degrade catalysts.

On the other hand, "modern" catalyst-equipped fuel injected engines don't need as rich an additive package because they have much better fuel flow control, so they don't wash down the cylinder walls or contaminate the crankcase with fuel like vintage cars with carbs that run, on average, much richer than modern EFI cars, especially during cold start and warmup.

From the standpoint of emission control systems, any O2 sensor-equipped engine is "modern". If it doesn't have an O2 sensor it's "vintage". The first O2 sensor car in the US was 1979 and most had them by the mid-eightes.

For my non-catalyst cars I use Chevron Delo 15W-40, which is a heavy duty diesel engine oil with an API CI-4 rating. For my "modern" cars with catalysts I continue to use motor oil designed for modern spark igntion engines, and the current API spec is "SL".

Regardless of your annual mileage I recommend that you change the oil and filter once per year and time the change before winter storage (if you store during the winter) or at the end of the driving season, when cars usually see less use until the following spring.

The brake fluid and antifreeze should also be changed on a time basis (every couple of years) regardless of miles driven.

Duke

[Stephen W.]

Re: FLUIDS

One tip on those trans pans ( and any tin pan or cover) Once you have cleaned the pan don't forget to straighten it. Use a small hammer to gently tap those bolt holes down to make them flat again. I like to back up the pan with a large socket. The key word is gently tap them down flat.

[Terry M.]

Re: FLUIDS

For spark ignition (SI) oils the latest API standard is SM. It started the first of the year, that is for oils brewed beginning in 2005. There is probably a lot of SL oil still in the supply chain, but look for SM. It is showing up in the mid-west already.