Mismatched gear ratios in differentials M998

[AOR]

if the rear end is fried you aren't driving it anywhere.
Either jack it up and rotate the wheels and count driveshaft rotations to figure out the gearing, or pull the differential out and pop the cover to check and count all the teeth on both the ring and the pinion to figure out the ratio.

Sometimes the wrong tag ends up on the wrong piece of equipment, or sometimes if a motorpool needs parts and they have a truck that's getting disposed of, they'll take whatever parts they need, and toss whatever the worst parts they have into the disappearing truck and call it good. Not their problem after that.

Without physically verifying what the gearing is, it could be anything.

most of the time there will be numbers stamped into the ring rear which is easy to see with the cover off when rotated in the correct viewing area its an AMC 20 mine had them just unbolt the cover no need to remove the diff itself rotate it look for numbers example 41 10 you divide the small number "pinion" into the big number "Ring gear" comes up as 4.10 if no numbers found count the pinion teeth and ring gear teeth and divide that way but 1 tooth off can get you the wrong ratio

 

[rakhav]

most of the time there will be numbers stamped into the ring rear which is easy to see with the cover off when rotated in the correct viewing area its an AMC 20 mine had them just unbolt the cover no need to remove the diff itself rotate it look for numbers example 41 10 you divide the small number "pinion" into the big number "Ring gear" comes up as 4.10 if no numbers found count the pinion teeth and ring gear teeth and divide that way but 1 tooth off can get you the wrong ratio

Okay. Well send me your info and I'll make contact about purchasing the part. If this is a private site ,let me know and I'll forward counts tong mumbrt

 

[Action]

most of the time there will be numbers stamped into the ring rear which is easy to see with the cover off when rotated in the correct viewing area its an AMC 20 mine had them just unbolt the cover no need to remove the diff itself rotate it look for numbers example 41 10 you divide the small number "pinion" into the big number "Ring gear" comes up as 4.10 if no numbers found count the pinion teeth and ring gear teeth and divide that way but 1 tooth off can get you the wrong ratio

not one punctuation mark...

 

[rakhav]

Thank you very much.

 

[86humv]

Inside on ring gear : 41 16 is 2.56
.....................................41 15 is 2.73
.....................................40 13 is 3.08

 

[rakhav]

Inside on ring gear : 41 16 is 2.56
.....................................41 15 is 2.73
.....................................40 13 is 3.08

Thank you much. Hope this one uh s 2.56 since it's an 86. I havent taken it apart yet.

 

[azulrios]

I have a '86 M1025 that has 2.56 (41 / 16) ratio. I had understood that the geared hubs had a ratio of 1.92 : 1 . I am not sure that I am correct, these may be 2 : 1 as mentioned above.

To remove the differential covers, I believe, one needs to procure the revised brackets.

REFERENCE TO; TM 9-2320-280-20-2 (CHANGE 2 – PARAGRAPH 6-52 & 6-53)

6-21. DIFFERENTIAL COVER MAINTENANCE - PROCEDURE APPLIES TO VEHICLES WITH NEW BRAKE ADAPTERS, P/N 10453002 THE BRAKE ADAPTERS ARE CUT AWAY, WHICH ALLOWS ACCESS TO LEFT CENTER CAPSCREWS

2530 013 14 1129

22075

10453002

ADAPTER, BRAKE VALVE LEFT AND RIGHT REAR, USBL EFF 1 THRU 44824 (I ALSO USED THESE FOR THE FRONT)

 

[Eoddave]

My front differential needs to be replaced. I can't figure out what ratio it is on my M998. Where can I find a part number stamping? Is there another easy way to figure out what I have?

 

[AOR]

My front differential needs to be replaced. I can't figure out what ratio it is on my M998. Where can I find a part number stamping? Is there another easy way to figure out what I have?

If the ID tag with ratio is not bolted to the diff with a cover bolt you can remove the cover the ring gear should have numbers stamped in it which will tell you the amount of teeth on the ring and the pinion gear. If not count the teeth of each gear and divide the amount of pinion gear teeth into the ring gear teeth
example is 41/10 is a 4.10 ratio

 

[Eoddave]

If the ID tag with ratio is not bolted to the diff with a cover bolt you can remove the cover the ring gear should have numbers stamped in it which will tell you the amount of teeth on the ring and the pinion gear. If not count the teeth of each gear and divide the amount of pinion gear teeth into the ring gear teeth
example is 41/10 is a 4.10 ratio

Thank you Sir. I now have a project for this weekend.

 

[Retiredwarhorses]

My front differential needs to be replaced. I can't figure out what ratio it is on my M998. Where can I find a part number stamping? Is there another easy way to figure out what I have?

simple….if its an A0-A1, it’s a 2:56