M998 broken spring replacement?

[jjb]

I recently purchased an M998 at the time I did not notice that the right rear spring is broken. How do I identify which spring it is? I am hoping to just replace the bad one. The rest of them all look fine. I did search the forums and couldn't find anything relevant.

Is there a way to identify which one I have? I see lots of them online but there are a few different part numbers.

According to the TM's there are 3 different part numbers.

 

[Mogman]

Well, let's see.
You said M998 not M998A1 so the UOC (usable on code) for the M998 is H13 (all models applicable to a particular parts TM is listed a few pages after the TOC, table of contents)
After downloading the parts TM which is free here on this site and you confirm the UOC then you look up under group 16 , 1601 "springs front and rear" and then go to that page, figure 192, and then drop down to the part numbers on the following page and this is what you will see.


You will notice three different rear springs listed, but only one has the UOC of H13, there are two different numbers you can search for, the first (3) is the NSN number and the second (5) is the manufacturers part number. (12338316-2) in your case.
You will also notice that all vehicles covered in this parts TM have the same front springs, that is why there is only one part number and no UOC codes listed for it.
This is a little confusing at first but if you download the TMs and use them it will become much easier over time.

 

[Mogman]

Here is a link to the TMs, the first 7 should be downloaded as they are the most significant ones applicable to your M998
https://www.nsnlookup.com/equipment-intelligence/land/hmmwv

 

[jjb]

Here is a link to the TMs, the first 7 should be downloaded as they are the most significant ones applicable to your M998
https://www.nsnlookup.com/equipment-intelligence/land/hmmwv

Awesome, Thank you for the info. I already downloaded them. How do you tell which UOC code applies?

I am pretty familiar with TM's but its been awhile. I replaced an engine in a HEMTT M977 and quite a bit of troubleshooting and repairs to an LMTV.

 

[Mogman]

several pages under the table of contents in the parts TM you will find this table, just look up your vehicle and voila!!

 

[jjb]

several pages under the table of contents in the parts TM you will find this table, just look up your vehicle and voila!!
View attachment 917458

Sorry, I realized after I posted that you mentioned that in your original reply. Thank you again.

 

[jjb]

I double checked the spring dimensions and they do not match the ones for 12338316-2 (At least what I can find online). They seem closer to 12338316-3. According to the data plate it was overhauled in 2005 and the serial number does not seem be correct as far as I can tell. It shows 700099. Would they have changed the serial number as part of the overhaul?

The wire diameter is about 1.3". It seems to be closer to 12342616 - 5360-01-357-2413.

The wire diameter for 12338316-2 looks to be just over an inch. Mine is definitely larger than that.

 

[mgFray]

Yes they often changed the data plate serial numbers on overhaul. Especially when they went fro M998 to M1097R1 and similar "R" models.

 

[Mogman]

I double checked the spring dimensions and they do not match the ones for 12338316-2 (At least what I can find online). They seem closer to 12338316-3. According to the data plate it was overhauled in 2005 and the serial number does not seem be correct as far as I can tell. It shows 700099. Would they have changed the serial number as part of the overhaul?

The wire diameter is about 1.3". It seems to be closer to 12342616 - 5360-01-357-2413.

The wire diameter for 12338316-2 looks to be just over an inch. Mine is definitely larger than that.

Post a pic of the data plate/plates

 

[jjb]

Here you go

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[Mogman]

Yes they gave it a new serial number, the MWO was for a bumper reinforcement for the 1097/1097A1 and some of the A2 trucks.
I would say it is possible they rebuilt it to 1097, heavy variant specs but did not change the GVWR for some reason, does it look like they possibly stamped over the original serial number? It may have been engraved instead of stamped which would be much less "deep"
So it may have the 10,000lb springs witch would be the first (UOC A13) springs.

 

[jjb]

Is the serial number anywhere else on the truck?

I don't see any old numbers. Maybe they replaced the data plate too?

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[Mogman]

No the serial number is only on the data plate.

 

[Mogman]

I am curious how you know it is a M998? does not seem to be listed on the data plates.
I would say if it has a air lift rear bumper it is a "heavy variant" after rebuild, maybe they did not have any applicable data plates available.

 

[jjb]

The plate on the passenger door says M998 and govplanet had it listed as a 998.

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[86humv]

Thats one of the truck like a 1097r1....early truck with later master cylinder, 10k axles, A2 rear bumper and variable rate rear springs....which should be replaced as a pair.....so manual won't reflect properly for a stock 998.
Springs you need are: 12342616

 

[jjb]

Thats one of the truck like a 1097r1....early truck with later master cylinder, 10k axles, A2 rear bumper and variable rate rear springs....which should be replaced as a pair.....so manual won't reflect properly for a stock 998.
Springs you need are: 12342616

Thank you for the info

 

[Coug]

One thing to mention is there are 2 different types of spring mounts for the rear. Most commonly referred to as cast and stamped/welded.
Cast are just that, a chunk of cast steel.
stamped/Welded are thick sheet metal bent into shape and welded up.

The cast use a longer spring than the stamped, so not interchangeable. You might want to verify which one you have before ordering springs as sometimes they do funny things when "upgrading" trucks and you don't actually know what's there without verifying.

Just to use my truck as an example, it's an M1123 that had the MAK (marine armor kit) installed, and part of that involved changing to heavier suspension. Talking to the experts that have seen hundreds of these trucks come through their shop, about 1% might have different lower control arms than the rest. Mine happens to be one of those 1%
I've also seen multiple engines that don't follow what serpentine belt system that the serial number says they should have, because once again, when they go through any type of rebuild, all bets are off.

So just take a look and verify what spring mounts you have. I believe all the early trucks should have the stamped/welded spring mounts, and springs are same length front and rear in the truck.

 

[jjb]

One thing to mention is there are 2 different types of spring mounts for the rear. Most commonly referred to as cast and stamped/welded.
Cast are just that, a chunk of cast steel.
stamped/Welded are thick sheet metal bent into shape and welded up.

The cast use a longer spring than the stamped, so not interchangeable. You might want to verify which one you have before ordering springs as sometimes they do funny things when "upgrading" trucks and you don't actually know what's there without verifying.

Just to use my truck as an example, it's an M1123 that had the MAK (marine armor kit) installed, and part of that involved changing to heavier suspension. Talking to the experts that have seen hundreds of these trucks come through their shop, about 1% might have different lower control arms than the rest. Mine happens to be one of those 1%
I've also seen multiple engines that don't follow what serpentine belt system that the serial number says they should have, because once again, when they go through any type of rebuild, all bets are off.

So just take a look and verify what spring mounts you have. I believe all the early trucks should have the stamped/welded spring mounts, and springs are same length front and rear in the truck.

I measured the wire diameter of the spring and it's roughly 1.3". According to what I can find for spring dimensions there is only one that matches. Unless there are more than what are listed in the TM?

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[Coug]

I measured the wire diameter of the spring and it's roughly 1.3". According to what I can find for spring dimensions there is only one that matches. Unless there are more than what are listed in the TM?

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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.