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Re: To Brownie or not to Brownie
DavidBraley #1376020 Sat Sep 05 2020 04:28 PM
Joined: Jul 2014
Posts: 234
1
Shop Shark
This sounds like a really interesting project. I'd like to travel faster too in my 3800 with camper but I'm unwilling to pay the fuel bill. I run right around 60MPH at engine 2850RPM. The brownie has a 17% overdrive and 24% underdrive plus direct. Gas mileage before 10% alcohol was added was ~11.5 MPG. Now it's barely 10. As I travel east from Washington State gasoline prices go down and speed limits go up. When I hit Idaho it's 75. When I hit Utah for a while the sign said 85 but now it's 80. Montana now has a speed limit on interstates, 80MPH, at least on I15 north of Idaho. Last month when I drove to Salt Lake City air temperature was around 100. I was concerned about tire temperature and held speed below 60. I'm right at the limit of tire capacity at max inflation pressure. On interstate 84 there were many alligators (chunks of truck tire) to dodge in the slow lane particularly at the bottom of hills. Guys blow by me in the hammer lane like I'm standing still; then an hour later I pass them sitting by the side of the road with the triangles set up. It's a long way from Sublett, Idaho to the nearest tire repair shop. Super singles are not your friend out here.

So aside from oil starvation in the rear axle, there are other considerations to traveling at modern interstate speeds. I added oil temperature gauges to the engine, brownie and soon the rear axle. Big trucks (class 8) have such gauges and they are not to be ignored. Climbing mountain passes temperatures go up by 100 degrees or so over the flats, much more than that and you've got bearing beginning to fail. Mind you these are manual gearboxes. Automatics are a different story.


51 3800 PU, 55 235 (w/cam, headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.
Re: To Brownie or not to Brownie
Hotrod Lincoln #1376021 Sat Sep 05 2020 04:42 PM
Joined: Feb 2016
Posts: 70
D
Wrench Fetcher
Originally Posted by Hotrod Lincoln
OK- - - -it looks like you've got the torque problem addressed, if not completely solved. Do you plan to do any dyno work before you assemble things? I'd be looking for a very flat torque curve, one that will avoid having to downshift frequently. With a Brownie and a 2-speed axle, you'll have a good variety of ratios to choose from, and probably even a few selections that won't be needed if you make good choices of camshaft and ignition timing.

Do you have a crankshaft grinder yet? I might be able to help out on that subject, but that conversation would be better by PM.
Jerry

Jerry,

The only dyno I have close to me is a chassis dyno (It's actually just across the street from me). I would prefer an engine dyno, but anything would be helpful to know what's up. I'm told the engine will make more torque than horsepower. The cam choice will cause the engine to start to fall off at around 5,200 RPM, and the sweet spot for towing up a steep grade under heavy load to be somewhere around 3,600 to 3,800 RPM. Conservative estimates are 500 max HP at 5,100 ish RPM, and 550 foot pounds of torque at 3,800 ish RPM. I'm also told to expect at least 450 foot pounds of torque at about 2,000 RPM. We will see. The EFI will help me extract more power from this engine more safely. Being able to electronically detect detonation and control spark advance prevents damage under less than ideal conditions.

I will read your PM.

Thanks,

David


-David

1953 2-Ton GMC

Horsepower determines your speed when you hit the wall. Torque determines the size of the hole you make...
Re: To Brownie or not to Brownie
DavidBraley #1376039 Sat Sep 05 2020 07:42 PM
Joined: Feb 2004
Posts: 21,052
H
Boltergeist
A trick we used on the dirt track cars was to use a small cooler for the rear axle lube- - - -made from the condenser coil for a mini refrigerator. The flare fitting for the flex tubing from the rear end to the cooler was drilled and tapped into the rear end housing where the spray from the ring gear gave enough pumping action to move the fluid, and the return line was plumbed into one of the axle tubes near the center section. It made a LOT of difference in the rear end temperature.

Too bad you're not closer to Tennessee- - - -I've got a water brake bellhousing dyno that has handled up to 700+ HP so far.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: To Brownie or not to Brownie
DavidBraley #1376053 Sat Sep 05 2020 10:04 PM
Joined: Feb 2016
Posts: 70
D
Wrench Fetcher
1Ton_Tommy and Hotrod Lincoln,

Great ideas on managing rear axle gear oil temps. EdPrus also suggested running a synthetic gear oil. If a person where to run synthetic gear oil, monitor temps and actively cool the oil, it all sounds like a great way to make the rear diff last a lot longer to me!

So now I've got good news, and bad news...

Good News first!

I think my worry about the pinion speed being to high is not as bad as I thought. This is what I've learned:

I decided to compare the Eaton 1350 2-Speed in my 53 GMC to a more modern comparable rear axle (in ring and pinion size that is). The Dana S110 and S135 commonly found in the Chevy/GMC 4500, and 5500 trucks, and the Ford F450 and F550 trucks (both respectively class 4 and 5 vehicles) have a ring gear of 12.5" in diameter. My 1350 has a ring gear of approximately 12.25" in diameter (I know, the 1350 is ancient, so maybe a poor comparison).

So how fast does the S110/135 pinion spin at 75 miles per hour? For my example, I chose a 2002 F550 with the V10 gasoline engine. The factory rear gear ratio is 4.88 to 1, and the stock tire size is a 225/70R-19.5. This tire is 31.9 inches in diameter. The truck is built to cruise at 75 miles per hour all day long. With a 4.88 ratio S135 and a 31.9" diameter tire, traveling at 75 miles per hour, the pinion is spinning at 3,855 RPM. My Eaton 1350 with a 5.83 ratio and a 38" diameter tire, traveling at 75 MPH, spins the pinion at 3,866 RPM. Only 11 RPM difference. I consider that good news for sure.

And now the bad news!

I drained the gear oil out of my 1350 this afternoon and immediately suspected I had a problem. The first half gallon of liquid that came out was water! I then pulled the rear diff cover off, and after careful inspection, the ring gear is in really bad shape. Because the main ring gear in my truck is heavily worn, I predict the pinion will be in much worse condition. The pinion gets an additional amount of wear, multiplied by the ratio of the two gears. So in my case, my pinion will be 5.83 times more worn out then the ring gear!

Aren't these old trucks so much fun!!! And we roll with the punches... LOL!!!

But seriously, there are very few things in life more satisfying then solving problems.

Take care everyone!

David


-David

1953 2-Ton GMC

Horsepower determines your speed when you hit the wall. Torque determines the size of the hole you make...
Re: To Brownie or not to Brownie
DavidBraley #1376067 Sat Sep 05 2020 11:45 PM
Joined: Jun 2011
Posts: 3,631
E
Shop Shark
David, the ring gear extends to the bottom of the case, however, the pinion only extends part way down, so, perhaps the pinion didn't get wet with water, however the bearings are a different situation.

Ed


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Re: To Brownie or not to Brownie
DavidBraley #1376083 Sun Sep 06 2020 01:23 AM
Joined: Oct 2019
Posts: 251
T
Shop Shark
I don’t know how your doing your calculations but I’ve found this site to be a great way to calculate rpm vs speed at various gear ratios:

www.4lo.com [4lo.com]

Last edited by Tony292; Sun Sep 06 2020 01:24 AM.
Re: To Brownie or not to Brownie
DavidBraley #1376086 Sun Sep 06 2020 01:47 AM
Joined: Feb 2016
Posts: 70
D
Wrench Fetcher
I use the Wallace Racing Automotive Calculators site.


-David

1953 2-Ton GMC

Horsepower determines your speed when you hit the wall. Torque determines the size of the hole you make...
Re: To Brownie or not to Brownie
DavidBraley #1376190 Sun Sep 06 2020 11:34 PM
Joined: Jul 2014
Posts: 234
1
Shop Shark
The cheapest and quickest thing to do is scout your favorite truck wrecking yard for a suitably heavy axle assembly. If you're lucky it'll have the same U-joint flange. Also it would be nice to not have to move the spring saddles. You may even have some choice of Gear ratios. Forty years ago I got one out of a GMC450 and put it in a 57 350 but I had to buy a 12V shift motor. The 450's was 6 volt and spun way too fast. Once the dust settled it ran until the owner died about 10 years ago. He called once to see what oil he should put in when he changed it. He hauled lumber for his construction business. He worked it all that time.


51 3800 PU, 55 235 (w/cam, headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.
Re: To Brownie or not to Brownie
DavidBraley #1376228 Mon Sep 07 2020 03:13 AM
Joined: Feb 2016
Posts: 70
D
Wrench Fetcher
1Ton_tommy,

I love stories like that. EdPruss has turned me on to several yards near me that I'm planning to check out. It's funny, I've lived here in Fort Collins for 30 years, and until now, I've never had a need for a wrecking yard. I'm sure something will turn up.


-David

1953 2-Ton GMC

Horsepower determines your speed when you hit the wall. Torque determines the size of the hole you make...
Re: To Brownie or not to Brownie
DavidBraley #1377060 Mon Sep 14 2020 10:58 PM
Joined: Oct 2010
Posts: 47
8
Wrench Fetcher
This is awesome, I had the same idea with my '56, I had a spare 454 lying around so we built it to run like a diesel. Conservative compression, but a nice cam profile that dynos at 408hp but makes 525ft-lbs of torque at 2,700rpm. Great vacuum, nice idle, and pulls from 600RPM to 6,000RPM with a super flat torque curve.

I'm running 22.5 tires also, I really like them. Handles great on the highway.

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