82 Chevy C-10 rear end gearing

[corymunson]

:) I have picked up a 82 C-10 6.2L with a 4 speed o/d A833 manual trans and rear end code of GQ1. It has 16000 original miles verified by carfax. 1 owner and used on a farm here in Georgia. I think it has 2.73 gears in the rear end because it will not accelerate in 3rd gear on flat level road pulling a 5000lb trailer. I am trying to find out what the optimal rear end gear for towing and and good MPG would be. :confused:

[john8662]

The perfect gear ratio for stock sized tires (235/75 R15's) is 3.42, good fuel economy.

For pulling 5k regularly, I'd suggest 3.73 gears, which will still grant decent fuel economy running empty.

2.73's really won't allow you to pull a stump out of the ground, or 5k at highway speeds with a tail wind ;)

GM geared a LOT of these 6.2's will TALL gears, mainly cause the target was maximum fuel economy, later on, they wouldn't pull well and the owner usually suspected the poor diesel engine under the hood. It's the gears.

J

P.S. Welcome to TDP's forums!



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[moondoggie]

Good Day!

My 82 has 3.08 gear; of course, yours maybe different... It has the New Process 4SPD with 4th being OD (3rd is direct). If it's the same as mine, I'm surprised you can pull a boat trailer with no boat in OD - I couldn't. :eek:

Blessings!

[corymunson]

Yes I be leave my gear ratio is 2.73 or 3.08. Which ever it is it won't pull my travel trailer any faster than 50mph on level road. I am thinking of trying to find a 3/4 ton axle with the gearing I want. I plan on going with 3.70s to 4 some thing. I feel this will give me the pulling power I need. So far I have not found a lot info in the A833 trans. Some say its a light truck trans not good for towing. I find this hard to be leave. Has anyone had problems with this trans for towing?

[moondoggie]

Good Day!

I think I might have had this same tranny in a 70's or 80's mid-size Plymouth with a slant six. I've been told it's a New Process, which was a joint venture between GM & Mopar. I've also been told it's pretty lightweight, & to NEVER tow in OD; no idea how much of this is true or not. Good news is, a 6.2 NA truck with this tranny & a tall diff is never gonna tow anything in OD anyway. :eek:


Blessings!
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[corymunson]

So far the research I have done has shown the A833 with the aluminum case can be weak. I have a cast iron case with aluminum tail shaft case. Also it looks like to me that the use of ATF fluid instead of gear lube would be a cause of wear and make it the weak link. I drained mine and only found a few steel filings. I refilled the Trans with 1 qt of Lucas and then ATF to finish the refill. But it still looks like I will be towing in 3rd gear most of the time. I am going to start looking at my local salvage yards for rear ends does anyone have a good idea what the price range should be for a ½ ton rear end. Thank you all for the help.:)

[moondoggie]

Good Day!

"Also it looks like to me that the use of ATF fluid instead of gear lube would be a cause of wear and make it the weak link." Before I knew it was supposed to be ATF, I changed it out for gear lube; it got so stiff I almost couldn't shift it. Hard to believe it made that much difference.

Blessings!
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[DmaxMaverick]

Gearboxes (trannies, TC's, etc.) that require/recommend ATF do so for more than just one reason. There is usually a pump involved, and I think we'll agree, ATF pumps a lot easier than 90 weight gear oil. In most cases, the pumps are plastic, and either won't pump 90W, or die trying. Some trannies, like the 833, IIRC, has an oil slinger. Well, 90W doesn't sling well, either. ATF may not lube as well as gear oil, but it has to be able to get there to be any good. Also, if the gearbox is designed to use ATF, the tolerances will be too tight to allow heavier oils to do any good.

If you fill with too heavy oil and it doesn't shift or makes noise, it isn't complaining because the oil is too thick. It's because there is no lubrication where it needs to be.

[moondoggie]

Good Day!

Yup, I only took one short trip with gear lube in 'er; got it replaced with ATF pronto.

Blessings!
(signature in previous post)

[corymunson]

I have about 2 1/2 quarts ATF and 1 quart Lucas. The Lucas is supposed to mix with ATF so we will see as I get some miles on it. So far the Trans does not feel any different. I found a place that rebuilds these transmissions and am going to call them to get their advice. If I get anything note worthy I will post it.:)

[corymunson]

Well I tore down the rear end and it had 2.73 gears. I'm in the middle of swapping them out for 3.73s. I am doing the alignment of the ring and pinion and the contact pattern on the grease on the drive side is centered and toward the toe. On the coast side the mark is on the toe side almost to the center. To me it looks good for forward but in reverse the contact seems to be on the toe of the gear. Any of you that have setup rear ends have any advice. :confused: