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Review: Shaftmasters Direct Bolt-in Aluminum Driveshaft P/N FMS1517GTM35D

wildcatgoal

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Maybe a couple weeks ago now, I purchased the new Shaftmasters Aluminum Driveshaft. I waited on this one because it is a direct bolt-in. That means NO adapters that just add weight and the reputation of the company seemingly was solid. And it wasn't going to be priced at $1,000 for an aluminum tube and some U-joints. And they're based in Michigan and I went to college in Michigan. :clap2: I paid $699.99 for it plus I think very reasonable shipping.

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This is the new driveshaft compared to the old. It is SIGNIFICANTLY lighter. Like... hold it dainty-like in one hand walkin' on a cool summer morning light. That makes sense, right? Anyway, including with the driveshaft were the mounting hardware (3 hex bolts; 6 12 point bolts; washers), a 10mm 12 point socket, and a 10mm thread chaser to clean out the threads at the differential. I was pleasantly surprised Shaftmasters included the socket and chaser!

The instructions were well written but did not provide torque values, which always ticks me off. It was unfortunately 10PM at night when I was installing this, so I couldn't get a hold of Shaftmasters to ask. I decided to research installation videos of other company's driveshafts, found the closest looking driveshaft, and used those torque values. I did 76 torques for the three (3) transmission output shaft bolts and 45 for the six (6) pinion bolts. It was NOT easy getting even the supplied 10mm socket on the six rear bolts on account of some part of the U-joint always being in the way, but them there trusty swivel sockets saved the day.

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Above is what she looks like installed. Because I have the Solo Performance exhaust, which is a mid-muffler design, I did have to drop my exhaust. I'd imagine you can probably avoid doing so with other systems, but it'd be frustrating to work around. Note there are no useless stickers or welded-on plaques with the name Shaftmasters emblazoned into it. Just a driveshaft... which is all I need. :clap2:

The Results
When I installed this, my engine was lowered .5". During heavy acceleration between 3-4.5K I was getting some relatively minor but still "concerning enough" vibration. I spoke with Shaftmasters, told them my setup, and they suspected it was the lowered engine. I also contacted SteedaTech and asked them if they experience anything similar with their S550 that has an aluminum driveshaft and asked about what the driveline angles would end up being lowering the engine. I also benefited from a few Atlanta S550 members who know more than me about driveline angle rules and regulations. With all these learnings in my head I went to the shop, did some driveline angle-finding. Here were my results:

Driveline Angles with Engine Lowered .5"
- Output Shaft (Transmission) - 2.3°
- Driveshaft - 3.6°
- Pinion (Differential) - 3.4° (opposing)

My understanding is that, static, the difference between the output shaft and pinion should be as close to 0° as possible, but certainly 1° or less. So I did some geometry in my head and debated shimming the transmission crossmember or raising back up the engine. Since I didn't have shims, I raised the engine back up to stock height (which is a relatively quick process with Steeda engine mounts and my beloved swivel sockets :headbang:).

[Driveline Angles with Engine at Stock Height[/i]
- Output Shaft (Transmission) - 3°
- Driveshaft - didn't bother measuring
- Pinion (Differential) - 3.1° (opposing)

So expecting some ° margin of error, raising the engine back up brings the driveline angles in perfect spec. Perfect! So I went back on the road after making this adjustment and... waammmmyyyyy the vibration was gone!

Performance Review
On the highway, cruising, I'm going to venture as far as to say "smoother than stock by a little bit". During acceleration, there is some NVH (specifically the N part) just on account of losing a big huge rubber guibbo from the stock driveshaft and me having spherical bearings and frame bracing and all that jazz in the back and firmer engine mounts. But there is no vibration. The car now feels like a proper sports car - tight, quicker to respond to what I'm flippin' telling it to do, you get just that right amount of engine/driveline/RPM-type feedback from the chassis that I have been chasing (hence the engine mounts and all the bearings and delrin bushings and what not). The driveshaft made the car feel... natural. And quite honestly, I've jumped up the "Are you finally content, man?!" meter a lot. I think some front upper control arm LCA bearings and I might have it!

The car is certainly snappier. I wouldn't say it's "super duper faster" but it does react to your inputs instantly now. Clunks going into gear and so forth are all but gone (my engine mounts helped this a lot, too). I haven't heard the usual clunks in days, guys and gals. What a relief that is! We'll see if this makes me a super great drag racin' somabich, but... prolly not. :)

Hope this helps...
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Jmeo

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Nice write up :thumbsup:

If I didn't have the DSS carbon fiber shaft I would get this one thats for sure. Luckily for me I have zero NVH with the CF shaft but I do wish they would make a true one piece design just because.
 

Mootang

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Excellent write-up, helps a lot!
 

armykyle1 [HACKED ACCOUNT

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I like the revised setup. I wish mine went as good as yours, but I have the old style and I have to ship it back due to bad vibrations above 70mph. Great review.
 

keltymd

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I too installed this shaft a week ago and love it. There is more N, as he stated, when accelerating hard but other than that no more clunk and it is as smooth or smother when cruising. I do have what sounds like VERY slight binding when accelerating hard in 1st and 2nd from about 3500-5000 RPM but I think that is due to the soft differential bushing allowing a HUGE swing in pinion angle at WOT. I have some Steeda 80 differential bushings on the way to see if I can live with the softer differential inserts NVH (the BMR inserts make way too much NVH on my car).

My pinion angle, shaft angle, and Transmission angle mimic Wildcatgoal almost exactly.
 

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wildcatgoal

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I too installed this shaft a week ago and love it. There is more N, as he stated, when accelerating hard but other than that no more clunk and it is as smooth or smother when cruising. I do have what sounds like VERY slight binding when accelerating hard in 1st and 2nd from about 3500-5000 RPM but I think that is due to the soft differential bushing allowing a HUGE swing in pinion angle at WOT. I have some Steeda 80 differential bushings on the way to see if I can live with the softer differential inserts NVH (the BMR inserts make way too much NVH on my car).

My pinion angle, shaft angle, and Transmission angle mimic Wildcatgoal almost exactly.
I'm convinced that if you put in some differential bushings, you'll lock up the differential mounts enough to solve that. I may put a GoPro under the car to see how the differential moves under heavy acceleration... that'd be interesting.
 

keltymd

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I'm convinced that if you put in some differential bushings, you'll lock up the differential mounts enough to solve that. I may put a GoPro under the car to see how the differential moves under heavy acceleration... that'd be interesting.
I am going to put a jack on the differential just in front of the pinion to get an idea of how much it raises under load. We know from the other videos is damn near bottoms out the bushings when you take off so that should be close to the load angle
 

09jsw

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So I have this shaft and just lowered my engine 1/2 inch to fit the cj intake. I have not gone wot yet due to tune but this post has me worried about the possible binding.
 

keltymd

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So I have this shaft and just lowered my engine 1/2 inch to fit the cj intake. I have not gone wot yet due to tune but this post has me worried about the possible binding.
once your tune is set go ahead and go WOT. You will know if its binding and can let off. If it is like mine it is VERY minimal and wont really hurt it. If it is bad just let off and you will be ok
 

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09jsw

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once your tune is set go ahead and go WOT. You will know if its binding and can let off. If it is like mine it is VERY minimal and wont really hurt it. If it is bad just let off and you will be ok
I'll try to pay close attention thanks
 
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wildcatgoal

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So I have this shaft and just lowered my engine 1/2 inch to fit the cj intake. I have not gone wot yet due to tune but this post has me worried about the possible binding.
Shim the transmission bracket in small increments until you get the right driveline angles. Then move on and have fun.
 

09jsw

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Shim the transmission bracket in small increments until you get the right driveline angles. Then move on and have fun.
THat was my plan so I'll stick with that.
I had planned to shim it down 1/8th already before the mounts became a thing.
 

keltymd

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THat was my plan so I'll stick with that.
I had planned to shim it down 1/8th already before the mounts became a thing.
I will say this. I shimmed mine down 1/8 (stock Motor Mounts) and it created more binding so I have removed them.
 
 




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