Top Recommended Driving Speed

I just recently got my truck road legal, and have taken a couple of short (30 min) trips to get the feel of everything. This truck is almost entirely stock, and I plan on keeping it that way. What is the top recommended driving speed to prevent problems with the t-case overheating? Seems like it is comfortable moving at 50-55 on a flat road, but I want to make sure this will not damage anything. I don't plan on taking any super-long trips, but an hour-long drive isn't out of the question. Thanks.

I consider 50 max cruise speed, but if necessary I'll hit 55 for a short time. I went on a 150-mile road trip in June, and had no transfer case issues using this guideline. The oil was at the proper level when checked at my destination.

Thanks Nailhead. I don’t mind going a little slower to keep the truck happy. Also let’s me take in a little more of the view while driving along :)

Top speed is going to depend on your particular truck. I have cruised at 65-70 with my sbc truck without problems. But my brakes are great, Michelin radials, and plenty of power. Lot's of wind noise though. So listening to the radio or talking to a passenger is not going to happen. Just smile and hum to myself.

I have had my stock truck cruising at 60 and it did fine on the flats. Had to slow down on the hills though. But it has michelins and well-maintained brakes.

With 500 hp, a hardtop and 4.56 gears with 40" tires you might cruise at 80.:happy10:

I took this picture in 1970, driving our M715 SVC-175 on the German Autobahn. Yes, that is how fast we really were going. Of course, the truck was only two years old and had new Goodyear tires on it. No shimmy.

http://i1067.photobucket.com/albums/...er1/Speedo.jpg

I do love that picture Don. I've seen it several times on here and thought about being 19 again and how the average 19 year old probably drove these trucks back in the day - when no one was watching.

Run whatever speed you want. As Kwai pointed out, each truck is different. My NP200 will go 45 miles at sustained speeds over 60 mph. Then I start to smell the gear oil vapor cooking out.

My happy speed with the Michelin tires is 52-54 mph. Which with stock tires would be 48 mph. I can and have driven hundreds of miles at that speed in a day with no issues.

We had a member 10 or 15 years ago who drove a stock M715 pulling a M101 trailer go from New Jersey to Washington state and back one summer. He posted just about every evening of the trip. Mostly with pictures of the speedometer at or above 60 mph. No issues of any kind.

Each truck is different. I would suggest an infrared thermometer. Drive whatever speed the truck and you seem happy at for at least 30 miles. Get a temp reading of the transfer case. If you are below 220° with mineral based gear oil, slow down for the next 30 miles and check again. I would say 250° for synthetic gear oil.

When I first put the Big Block 396/NV4500 in my truck I still had the stock tires and drove it 230 miles to the 2005 Texas FE. I had the power, so we were going down the road at 70 mph. 50 miles from home I was smelling the gear oil running with no top. I checked the case temperature and it was 289° and climbing with Mobile 1 inside. I did the next 50 miles at 48 mph. 210° case temp the next stop. That is how I found my happy speed.

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Originally Posted by Large

Also let’s me take in a little more of the view while driving along :)

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Exactly: if I want to drive fast, I'll do it in my '08 Power Wagon, radio blaring, A/C humming.

It's amazing how many cool old trucks can be found behind barns, under trees, etc., while dawdling along at 50.

All kidding aside, I don't advocate going much above 50 MPH. The transfer case whines enough at above 30 MPH and it really doesn't like going faster than 50 MPH. I took the picture of the speedometer in 1970 So, I was only 22 years old at the time.

In the truck that I have now, I will get a shimmy at any speed above ~48 MPH. I have swapped the tires around and it helps. What would really help would be to get them balanced. But the tire people around here are so afraid of split ring tires that they don't want them on their property.

As other comments were made, a lot of our members are much younger and accustomed to hydraboost power disc brakes, power steering, 6-speed automatic transmissions etc. So our trucks in stock form seem strange (and slow). But they are doing exactly what they were designed to do and usually do it well.

I am a stock guy and love to see it this way:

http://i1067.photobucket.com/albums/...vflyer1/lf.jpg

Picture taken summer of 1970 at Wiley Kaserne, Neu Ulm Germany. I put a lot of miles on that truck.