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Difference between M988 and the M998A1

biggdadd58

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Again, I am new here. What is the difference between the M988 and the M998A1? I am in the market for something and needing some education before purchasing. Any and all input will be greatly appreciated.
 
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ikoinu

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Wire Fox

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He said it was a typo but there are other red flags as well.
Probably avoid that listing, then... There's plenty of HMMWVs out there to buy, and many of them are right here in the classifieds section. The M998A1 has several improvements over the original that I'm honestly starting to forget (3-point seat belts, better transfer case, more reliable parking brake setup). Most of these improvements would actually be made to the older M998s if they ever went in for rebuild, as I can't think of any major improvements that weren't just an MWO that called for units to replace the "inferior" parts with the newer setup.
 

Lionel

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From AM General's site;

"A1 advances incorporated across the new production fleet included: new front seats, improved parking brake lever with safety release, metal hood grille, improved slave receptacle, solid state glow plug controller, modified rifle mounts and upgraded rear half shafts."

I know my '94 A1 also has the brake upgrade that incorporates the parking brake into the rear calipers, eliminating the propeller shaft disk brake. But this was apparently done at the "reset" for any 998.
 

Skrilex

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From AM General's site;

"A1 advances incorporated across the new production fleet included: new front seats, improved parking brake lever with safety release, metal hood grille, improved slave receptacle, solid state glow plug controller, modified rifle mounts and upgraded rear half shafts."

I know my '94 A1 also has the brake upgrade that incorporates the parking brake into the rear calipers, eliminating the propeller shaft disk brake. But this was apparently done at the "reset" for any 998.
Hmm no mention of the t case upgrade. My 998 was one of the very first 1985 and serial 11xx, yet it has the park brake and t case upgrades. Not sure about the hood grille and rifle mounts but I’m guessing yes. How can you tell on the half shafts and why was it only the rears?
 

Wire Fox

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Hmm no mention of the t case upgrade. My 998 was one of the very first 1985 and serial 11xx, yet it has the park brake and t case upgrades. Not sure about the hood grille and rifle mounts but I’m guessing yes. How can you tell on the half shafts and why was it only the rears?
It's definitely there, though. There were MWOs in-place to call for HMMWVs to be upgraded to those parts if the systems failed. The parts TM indicates exactly what models accept what parts. The original light duty HMMWVs get the older T-Case (NP218?). The A1 and beyond has an NP242. There's notes in there to basically ask what other components are installed, as the NP242 can have a different spline count, depending on your propeller shaft configuration. The yoke style changes from original to A1 as well. Only the rear brakes were upgraded because with the single propeller shaft disc brake for parking being deleted, the rear calipers needed to have a parking brake actuator assembly built into them, thus different parts. This is an improvement because now there are two holding points for the parking brake, plus you don't have a hot brake assembly right next to the fuel tank in case of failure.

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