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Old 06-18-2019, 03:37 PM   #1
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Seismic Leaf Springs Flattened

The leaf springs on my '16 355w have flattened out, see pic below.
I run right at GVW when fully loaded which I'm sure contributed to the sag. That and I'm sure they are not high quality springs to begin with.

So, since I need to replace the springs, I was thinking of upgrading the axles from 7k to 8k axles. Jayco started using 8k axles on the 355w in '17, so fitment shouldn't be an issue. It also would give me a little cushion from pushing the max axle rating.

Has anyone here done this? Any advice?

https://www.jaycoowners.com/forums/a...1&d=1560893776
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Old 08-13-2019, 06:20 PM   #2
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I decided to upgrade to the 8k axles. The shop has them installed and they look good.

The 8k comes with 3 3/8" brakes vs 2" on the 7k axles. I'm sure it should give me better braking performance. Hubs look stout!

The trailer is still at the shop waiting for a replacement wheel. Found a crack in the Tredit wheel that the shop caught while swapping the axles. This is the second wheel failure I have had on this trailer.
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Old 08-13-2019, 06:27 PM   #3
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I have friends who upgraded their axles from 6 to 7k, just not on a Seismic. Bolt on project from what I hear.
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Old 08-13-2019, 06:37 PM   #4
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That's exactly what mine was, direct bolt on replacement. Would have done it myself, but my shop only charged $230 for labor so I had them do it.
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Old 08-18-2019, 08:32 PM   #5
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Did you also upgrade to the 7 leaf springs that came on the newer 355’s?
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Old 08-18-2019, 09:33 PM   #6
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I didn't count the number of leafs. The new axles came as a complete assembly, with 8k springs.
I'll verify when I pick it up this week.
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Old 08-18-2019, 09:45 PM   #7
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Jayco upgraded my 377 to 8 leaf 8000lb springs. My nephew has a toy hauler that the springs flatten out on and did the same. Same axles but upgraded from 7000lb to 8000lb springs. Springs are cheap and easy to change. I would like the 3 3/8 brakes. My last 5er came with 8000lb dexters from factory but still had 2" brakes.
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Old 08-19-2019, 06:22 PM   #8
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The new springs are 7 leaf and supposed to be 8k rated. The 7k axle springs were 6 leaf.

And as a bonus, I sold the old axles today for $200 to help offset the cost of upgrading. Probably should have asked more because I had two guys wanting them and offered to pay asking price. I had no idea what the value for the old ones were and just guessed $200 thinkin I would come down if no interest.
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Old 08-19-2019, 08:26 PM   #9
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I didn't realize my rear leaf springs were looking like that on my 2017 355MBQS until one of them snapped while we were on the road. That wasn't a fun experience. I replaced both of the rear leaf springs (in a gravel parking lot 2-1/2 hours from home), the fronts looked OK yet. My axles were both 7000 lb Lippert. I'm now seriously considering a different suspension, not just different axles. Has anyone looked at or used either of these? https://timbren.com/axle-less/ https://timbren.com/silent-ride/ Looks like the silent ride could be cheaper / easier, but maybe the axle less would ride better.
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