Ugc fastback ....driveshaft issue

[day215]

I picked up a Fastback right before Juan closed his doors, awesome quality piece. I have read thread after thread on Fastback builds, I decided to follow the advice of those who know as I start my build. I am running my front and rear lower links at the same length as billj and dickyt, 5 1/16th rear and 4 1/4 front, measured eye to eye. My tranny has been flipped, spur forward motor on the right. My front reaches fine but the rear is about 1/2" too short. I run stampede shafts on axial yokes, in all the threads I have read, I have never seen anyone mention driveshaft issues. The rig is mocked up in a jig that sets my wheelbase at 12 1/8th, I can Frankenstein a new rear shaft, but I just wanted to know if I'm doing something wrong. I'm not running a dig, could this be the reason for the shaft being too short? Thanks for all the suggestion you can give.

[DickyT]

Lack of dig is why the rear shaft comes up short. Either frankenstein a pede shaft or get a dig

With a dig you may find the need to trim a little off the female side with pede shafts. I had to grind the collar on the male side of my mips up a bit.

[day215]

The man has spoken! Thank you, as I was typing, the dig issue came to mind, thanks for the uber fast reply.

[shizzz]

Two same questions the same day. Kind a tendency
Thank you, Richard, for the help.

[PipeDreams]

Even my MIP rear shaft is just barely long enough... I have maybe a 1/4 inch of engagement but it seems to be enough.

[day215]

A 1/4" should be enough with an MIP. I took a driveshaft for a Jato and combined two male splines sections, I threaded a 1" section of 8/32" all thread thru the center hole on the male ends and CA glued it to keep them from spinning. It looks like it will work, but dang that driveshaft is long, I'm hoping the extra leverage doesn't get the best of it.

[DickyT]

Originally Posted by PipeDreams

Even my MIP rear shaft is just barely long enough... I have maybe a 1/4 inch of engagement but it seems to be enough.

With no dig that will be the case. 1/4" is plenty with the strength of a mip

Originally Posted by day215

A 1/4" should be enough with an MIP. I took a driveshaft for a Jato and combined two male splines sections, I threaded a 1" section of 8/32" all thread thru the center hole on the male ends and CA glued it to keep them from spinning. It looks like it will work, but dang that driveshaft is long, I'm hoping the extra leverage doesn't get the best of it.

It should be fine. I ran spliced 'pede shafts while I waited for my Mips and VP dig to show up. it was not a long wait, but a good 12 hours on the rig during the wait with no issues.

[C*H*U*D]

Originally Posted by day215

It looks like it will work, but dang that driveshaft is long, I'm hoping the extra leverage doesn't get the best of it.

I ran Traxxas shafts with no problem, however the rear being as long as it is, eventually twisted enough to require a replacement. It looked like the striping on a candy cane, but that was after a lot of time on the truck.

[DickyT]

Originally Posted by C*H*U*D

I ran Traxxas shafts with no problem, however the rear being as long as it is, eventually twisted enough to require a replacement. It looked like the striping on a candy cane, but that was after a lot of time on the truck.

The great thing about trx shafts is when the do require replacement they are dirt cheap

[PipeDreams]

Originally Posted by DickyT

The great thing about trx shafts is when the do require replacement they are dirt cheap

Amen to that lol... ya I know the 1/4 is enough. It's lasted for a few runs out and it's spot on... honestly idk if it even has a 1/4 but it's enough to work lol.

[day215]

Sweet, I'll find out soon enough. A little off topic, but my rig seems to have a lot of lateral movement in the rear, I have chocked this up to the rear upper links running parallel to each other, I'm running a D mount in the rear. It flexes great and doesn't seem to cause any issues other than a slight sway side to side if you push on the chassis. Any thoughts?

[DickyT]

Are your uppers mounted inside or outside the chassis?

[day215]

Originally Posted by DickyT

Are your uppers mounted inside or outside the chassis?

Rear uppers are inside, front uppers are out. Would moving the rears to the outside help? I guess that would be slight triangulation.

[day215]

I moved my upper rear links to the outside at the chassis, the lateral movement is now gone, what a difference that small change made.

Can anyone give me a rough ride height to shoot for? I'm at 3" at the front of the skid and 3 1/4" at the back, it seems to be on par with most others, I am thinking about limiting the shocks but o wanted to get some input from those that have already ran this chassis.

[DickyT]

Originally Posted by day215

I moved my upper rear links to the outside at the chassis, the lateral movement is now gone, what a difference that small change made.

Can anyone give me a rough ride height to shoot for? I'm at 3" at the front of the skid and 3 1/4" at the back, it seems to be on par with most others, I am thinking about limiting the shocks but o wanted to get some input from those that have already ran this chassis.

Good deal, I was going to say outside on the rear. D mount + inside mounting will create the movement. As you said, outside gives a little upper link triangulation

I ran my FB comp rig at 2.75" at skid front and 3" at skid rear.

[day215]

Nice! I came across a screaming deal on some t-maxx shocks, 8 of them for 10 bucks brand new. I did the shock cap mod using a revo rod end and it made them a bit longer than I wanted, this is the reason for the increased ride height. They aren't the big bores I was hoping to get but the don't leak like my stockers did. I'll limit them a little and see how she runs. Thanks to everyone than stepped in with suggestions, its very much appreciated.

Thank you,
Daniel