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Same Old Van, Need More Advice

Another question about my 87 GMC van:

I'm have a rear axle that's making some noise. It's going to have to be repaired or replaced. I'm really dissatisfied with it anyway because it has

2.73 gears. This is in a 3/4 ton Full Size GMC van with a raised roof and 700r4. Overdrive is useless in the current configuration.

Using online calculators, I've figured that I currently turn only 1,550 rpm at 70 mph. That's great on flat ground, but I live in the mountains. The least bit of grade causes a downshift, or at least a TC unlock.

I'm going to change gears to either the 3.42 or 3.73. With the 3.42, the engine will be turning about 1,950 RPM at 70mph. With the 3.73, it'll turn about 2125 at 70mph. These are the numbers in OD with the TC locked.

I do at least 75% of my driving at interstate speeds (limit is 70 in WV where I live). Considering all this, which gear would you go with?

Thanks again,

CJ

Reply to
CJBrown
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Are you sure you calculations are right? You have really tall tires on it? All those RPM numbers seem low. If they are right I think I would go with the 3.73.

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Reply to
Scott M
3.42's if you don't tow

3.73's if you do

and put an auxiliary cooler on that 700 !!!!!!

Reply to
Gary Glaenzer

I'm running a slightly taller than stock size, 235/75R15. Believe me, the thing really turns that slow...

CJ

Reply to
CJBrown

he's correct

had a late-model K-1500 in last summer with 235's on it and

2.73's.........1650 rpm at 65 mph with TC locked up

what a dog.....and 4WD to boot and they towed a 4-horse trailer with it !!!!!!

Reply to
Gary Glaenzer

I don't tow, but I do load it down a bit with passengers and luggage often. My big concern is not so much the wear and tear of the higher rpm, but of that feeling that I'm constantly winding the engine up. That's why I haven't considered a 4.10, for example. Does that make sense?

CJ

Reply to
CJBrown

very good sense

just keep the transmission as cool as possible.....in your part of the world, a Tru-Cool 4590 or Hayden 1679 cooler will work wonders

Reply to
Gary Glaenzer

============= On that big heavy van I think I would go with the 4.73. It will keep your torque converter locked up more thus making it run cooler.

Reply to
Scott M

============== I hate when I do that, 3.73 not 4.73 LOL

Reply to
Scott M

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