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M998 broken spring replacement?
- Thread starter jjb
- Start date
I looked at the truck he got from govPlanet....it has cast spring mounts....its in the pics.Have you checked both the M998 manual as well as the M1114 manual, and made sure you had the newest versions?
Also to add, it does seem that there are multiple springs that aren't in either manual series, due to both the H1 commercial market as well as kits that were made for the HMMWV by the manufacturer.
To continue on my post from earlier, the springs with the cast upper mount have a longer free length than those with the welded mount. It's about 12" long free length for welded, 14" for cast. Installed should be around 10 and 12" respectively.
1.3" diameter spring would be constant rate springs for the M1114 trucks (RSCK18428-2), with a compression rate of 3000 lbs per inch. That's way too high for a stripped down unloaded truck, and won't even start to feel soft until you get up near the 10k lbs mark. Great for heavy loads, bad for your kidneys without load.
The M1097R1 trucks are mostly A0/A1 trucks that got rebuilt into the M1097 heavy variant, and it's not always clear what parts they changed out to do that.
it SHOULD have the cast upper mount, which means you have to use springs from an A2 or newer version of the truck, but as I said, without actually looking, you can't know for certain, and it kind of sucks to waste money buying parts you can't use.
Cast upper mount
welded upper mount
I've seen MAK equipped trucks with either cast or welded upper mounts and super heavy springs, so once again, you never know what they will do.
- 2,974
- 4,355
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- Location
- Olympia/WA
I believe that you'd want the A2 progressive rate springs as replacements. You definitely don't want the M1114 springs unless you're using it as a shelter truck or something similar with a lot of weight all the time.
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- 4,181
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- Location
- Brentwood, Calif
That’s a variable rate rear…look in the TM and look at the UOC code For correct application
- 2,974
- 4,355
- 113
- Location
- Olympia/WA
His is a 3 speed R1 truck, and has the cast mounts. The R1s don't have a UOC that I know of, and I didn't want to just assume for him that it was the same as the M1097A1 for those parts.
- 4,397
- 4,181
- 113
- Location
- Brentwood, Calif
casted uppers is always variable rate, started on the A1 model
- 6,928
- 9,584
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- Papalote, TX
It does look like your truck is actually an R1, I have no idea why the data plate they used did not reflect that, actually the data plate does not state any model and the weight rating of a basic M998, they obviously just got lazy and used what ever they had, the plate on the passenger side was just left over from the original truck and has no real meaning.
So it looks like you have the variable rate springs 12342616, this would be consistent with an R1 that was rebuilt to M1097A1 specs and would have a UOC of AVY
So compare the dimensions to that spring and as RWH said it is best to replace them in pairs.
So it looks like you have the variable rate springs 12342616, this would be consistent with an R1 that was rebuilt to M1097A1 specs and would have a UOC of AVY
So compare the dimensions to that spring and as RWH said it is best to replace them in pairs.
- 6,928
- 9,584
- 113
- Location
- Papalote, TX
In fact the NSN number 2320-01-107-7155 is for a M998 BASIC truck which would not likely have the cast mount and variable rate spring.
Yours is obviously a variable rate spring by the fact that the diameter of the coil tapers.
Yours is obviously a variable rate spring by the fact that the diameter of the coil tapers.
- 2,974
- 4,355
- 113
- Location
- Olympia/WA
the 700xxx serial number is more consistent with being an M1097R1 truck, as regular production HMMWVs are still under the 400xxx or so mark, and the M1097R1 trucks are 500XXX and up.