ive got a stock 87 dodge s/6 .5 ton. i use it as a dd along with moderate hauling activities associated with farming

it has a 4 speed overdrive with an open rear end and unknown axle ratio (but i am thinking it is probably 3.23's or possibly lower based on the low power)

The rear diff has developed a noise / growl / vibration when i make sharp right hand turns with the drivetrain under power. When i put the clutch in the noise stops. When i let off the gas the noise stops

Questions:
1. Is the transmission likely an 833? The linkage is getting sloppy and i need to rebuild / replace it

2. What is the likely source of the rear diff noise? I am thinking outer wheel bearings??

3. I have a good spare rear diff out of an 90 model dodge truck that is a 3.91 sure grip. What are your thoughts on installing this instead of fixing the other one. I am trying to evaluate the power / mileage tradeoff along with any other consequences of such a swap. If i do change it out i will need to replace the speedo gear and dont know what i need or where to order it.

thanks for any comments

Dean

The transmission is indeed an A833OD.

Diff noise could be wheel bearing related, but also could be spider gear related. The 3.91/OD combo is excellent; gives you an overall final drive ratio of 2.87. You would likely gain fuel economy and driveability/performancey if you're currently running with 3.21s or thereabouts. To determine which speedo drive pinion you need, you'll need to know your tire diameter. What size tires are you running?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dan
thanks for the reply. i was hoping you were on the board somewhere when i submitted the post

the tire size is p235-75r 15. Sounds like my best bet would be to just change rear diffs

one other question: my trannie sometimes has difficulty downshifting into low only when its cold. maybe wear on the synchro? Would changing the gear oil help? I recently changed it with the specified atf

thanks again
Dean

With that tire size and 3.91 rear gears, you need a 35-tooth speedo drive pinion. Part number 5206 8157 from the dealer or from www.chryslerpartsdirect.com (looks like Year One wants $70 apiece for these, which is well over double what you'll pay from chryslerpartsdirect or a friendly local dealer).

Synchro wear, yes. Changes to automatic transmission fluid that make it more suitable for use in automatics has made it less suitable for use in manuals. See if you can hunt up some Redline MTL instead.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks Dan

i will be installing the new rear diff and speedo gear. I will also try to find the gear lube you suggest

hope all is well up there


Dean

I had exactly the same symptoms you describe in down-shifting into first, and sometimes into second. Heck, sometimes up shifting into second as well. Same setup...1982 D150 "Miser" with an A833OD--3.56 rear end.

Although the transmission is filled with ATF at the factory the manual (Owners Manual and service manual) states that regular old smelly 80/90W gear oil can be used. I found that the following actions made shifting wonderful:

1. Drain the red ATF out of the the A833 transmission. Peer at the gear tooth(s) that you can see and remark on their clean, shiny nature. Note the different/not so lubricating qualities of the ATF as compared to slimy dead dinosaur gear oil. These oils really are different animals, although more than one car manufacturer specifies ATF-like oils in manual transmissions. The A833 can operate with either.

2. Fill the transmission back up with synthetic gear oil. I used Mobil One since it was handy. Redline has a avid following and is well thought of. You could also used regular Joe gear oil. Buy the pump/hose combination that screws into the top of the gear oil bottle. It is a nice way to move that smelly stuff from the bottle into the transmission. Ask yourself why synthetic gear oil smells as bad, if not worse than the "real" stuff. Try not to get any gear oil on you--wives respond poorly to its manly fragrance.

3. Remove the transmission boot (i.e. the chrome ring and the rubber boot) from inside the truck cab and clean the crap off the linkage--this is a case where blasting something with WD-40 is probably ok. A degreaser is what is needed here...you want to remove all of the old, funky, gummy grease from the shifting mechanism.

4. Marvel at the grease zerk you likely just noticed under the funky mess of dead grease, road grime, and other mung. Attach grease gun, pump, shift gears, pump grease, shift gears, repeat... Note the improvement in shifting just from greasing the shifter mechanism. You may find greasing from under the truck easier to do.

5. Drive your truck--shift firmly and slowly in those situations where it used to be hard. I drove about 1000 miles or so before shifting turned into what was expected.

I can easily down-shift into first from second gear at a reasonable speed/rpm, say maybe 15 mph or so. I was really shocked by how slick the shifting turned out--I thought the transmission was toast, i.e. dead synchros, etc. Turn out to be a case of just running the proper fluids and some TLC on the shifter mechanism.

The 3.9 sounds great...the overdrive with gearing less than 3.9 is mostly worthless unless you are on the flat and traveling at 70 mph or greater. If you did not already have a 3.9 rear end handy I would say look at a 4.1--that pencils out to ~3.0 final drive ratio...nice place to end up at RPM wise at a reasonable highway speed.

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Slanted D150

thanks tlrol,

i will try your suggestions. since i already have the 3.9 sure grip i will probably just use that for now.

my shifter linkage is also pretty sloppy and needs rebuilt or replaced. any suggestions here would also be appreciated

thanks again
dean

Not sure but try BrewersPerformance,worth a try.

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83 B-150 slant 6,4 speed. 79 B-300 360 pathfinder 4x4. 74 W-300 318 4x4 git-r-done 80 B-100 sl6,4speed

you can always try double-clutching on downshifts or throwing it in neutral and hitting the brake until you get your transmission sorted. think about it, with an automatic trans in Drive, the car is being propelled forward while hitting the brake, and even with four-wheel drums i am not changing linings enough to be bothered by it. even if i was, id sure rather replace brake linings than yank the trans out to replace the clutch and syncros.

people who downshift just to save the brake linings are complete fools. not only does it put additional wear on the clutch and syncros, it also causes the drive wheels to do the braking, which in poor road conditions with a rear-wheel-drive car is just ASKING for trouble. inertia shifts the car's weight OFF the rear wheels during braking. do you want to skid in a straight line or fishtail like a top?

Profoundly bad habit. Downshifting is only necessary during rally racing (read: Real, ACTUAL racing, not pretend racing on your way to work) OR towing a heavy load OR long downhill jaunts on twisty roads for the sole purpose of minimising brake fade caused by heat, NO OTHER TIME. maybe now's your chance to get used to double-clutching or neutral braking while youve got no other choice.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

i am lucky i guess in that my low gear sychro isnt that bad yet. It only grinds a little bit when i attempt to downshift when its cold. After warm up its ok. i will try changing to the gear lube that has been suggested and this will probably take care of this.

as for frequent downshifting you make a very good point. brake linings are a whole lot cheaper and easier to fix than screwing around rebuilding a transmission

thanks for all the suggestions
dean

before i swap my rear end i thought i would determine the ratio of the current rear diff.

as the tag on the rear diff is long gone, i thought one quick way to do this was to count the number of turns the drive shaft rotated relative to one complete revolution of the tire.

with the truck jacked up and in neutral, the rear tire marked at the 12:00 position, one turn of the drive shaft put the tire at the 7:00 position (i.e. approx 210 degrees). Two complete turns of the drive shaft had the tire rotated around once and landing at the 2:00 position (i.e. 420 degrees).

if i calculated this right, one complete 360 degree rotation of the tire would have the shaft turning only 1.7 times???

this doesnt seem right to me. what am i doing wrong?

thanks
dean

which tire and is the other tire also rotating, or stopped when you do this? if you stop one rear wheel the other will then spin twice as fast, because of the spider gears.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

one tire was jacked up the other on the ground.

with both tires jacked up the tires rotated in opposite directions (indicating an open diff) but the shaft didnt turn.

Trans in neutral, parking brake released. One tire blocked, one tire rotated through two full turns while you count quarter-turns of the driveshaft by noting how many U-joint caps come to face the pavement.

Divide that count by four and that gets you within very close range of the rear axle ratio.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

looks like i got a 3.55 then

14/4 = 3.5

aside from the savings assoc with not repairing the reaar diff on the truck now, will the 3.91 still help me?

thanks again for all the assitance

dean