2/7/03

QUESTION 1

Mike,

I have a question related to the 4L80E transmission in my tow vehicle, a 1997 one ton dually. Is it or is it not advisable to tow in overdrive? I have talked to experts in this area and I even took a transmission overhaul course at the local tech and they all say absolutely not. However, no one has been able to give me a real good explanation as to why not. GM doesn't mention anything in the owners manual and the local dealership doesn't know or won't say.

I understand that if the transmission keeps downshifting that it should be run in a lower gear, but I'm talking about cruising down the highway on fairly level ground in lower wind conditions. Part of my concern is that I have 4.1 gears and when I run in third gear, not only am I using more fuel, but the engine is turning 30 percent faster than in overdrive, which puts a lot of wear and tear on the engine.

I have a transmission temperature gauge in the cab and the temperature stays about the same (220 max) whether I'm in overdrive or not. The truck has the factory towing package with a separate trans cooler and engine oil cooler.

Any information would be appreciated. Thanks.

Tom Ales

Tom,

Let's use some common sense here. We have a temp gauge so we can see how hot we're running. If we aren't loading it hard on flat ground, why not run overdrive? There is no problem there.

When climbing a hill or on an incline, you need a tachometer to watch so you can set your rpm limits for each gear so you can also keep the engine at the sweet spot for pulling that particular hill.

I don't see any problem towing on flat ground in overdrive, just use your gauges and use your head.

Mike

QUESTION 2

Hi Mike,

I have a '50 Ford pick up with a 671 GMC blower on a 350 c.i. Chevy small block, two 700 Holleys boosting 8 to 10 lbs, a 350 turbo transmission, Boss Hog converter, 3500 stall, 4.56 rear drive, and 32/14.5 slicks. I footbrake to 2800 rpm -- any more and I push through the lights. When I leave, the engine goes to about 5,000 and stays there through the quarter-mile.

Tranny guys say I am driving through my converter. How can I keep my cost down and get the converter to hold? I run 11.80 at 109 mph. It seems like the truck should be a lot faster than that. It weighs 3,000 lbs.

Please help.

Terry

Terry,

With your blown motor combo you are making a lot of torque, so I agree that you're probably driving through the torque converter. Generally, blown set-ups will use a tighter converter than a normally aspirated one. You need to put a load on that power plant and get some of that power to the ground. The truck should pick up a bunch with a good converter.

Mike

QUESTION 3

Mike,

I'm just finishing up a four-year restoration on a 1959 Corvette. I have a question that has been driving me nuts! The car is quite original and it's a 245 hp 283 with dual quads. The car has the original cast iron Powerglide, which I had a local shop rebuild. However, I'm really suspect of the fluid level dipstick. Somewhere along the line, the handle portion has been broken off.

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I've researched a lot of the old Corvette books, and they show a gauge with a long pull handle with a loop on the end (kind of rod-shaped handle). My filler tube looks correct, however it's kind of short - maybe seven or eight inches long.

If I could determine when the transmission has been filled to a proper level, I'd just mark this stick and be on my merry way. The question is, are there any sight plugs on these old transmissions, or anything I could loosen up to check at least the cold fluid level?

I understand the Corvette Powerglide was a tad different from other Powerglides or that era and the dipstick may have been unique.

Any info would be much appreciated.

Tom

Tom,

The old Iron Glide is a tough unit, but it doesn't have an oil pan. You will notice the dipstick tube is short and fat. The area in the case where the oil sump is goes all the way across the bottom front of the trans. The fluid level in it should probably be one inch to 1.5 inches deep. To finish off your restoration job nicely, you really need to find the right dipstick.

Mike

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