FWD safe speed?

I need to run a little test to determine a vibration.

I am going to pull the rear driveshaft and go FWD for a day. I need to test at about 70mph. Just confirming this is safe.

And yes, SYE of course.

In what way are you concerned that it would be unsafe?

I would say 40 mph besides what kind of vibes do you have.........

The owners manual says not to exceed 50mph in 4wd. That would be include spinning just the front.

Not sure why you mention you have an SYE when you're pulling the rear shaft to hunt a vibe. The SYE does not effect the front output.

the owners manual says that because if you need 4wd, its going to be snowy. you can drive at any speed you want in 4wd, rwd, fwd etc. my stroker had the full time case and i hit well over 100 in full time

You will be fine so long as you have the SYE. Be prepared with only the front driving, there will be some wicked torque steer. I have driven with the front only on several occasions. First time had a lockrite in the front and about ended up in the ditch from when I steped on teh throttle. Threw in a set of factory spiders and it was cool, but still some bad torque steer. Also you can do some wicked FWD burnouts I was waiting on my rear driveshaft to come in just before I pulled the Dana 30 and install the 44 and lit the front tires up just because there was nothing to loose. The 30 had no issues with the 2ed gear tire smoking :rof:

AARON

Ah good questions...

The reason I ask:

I have the vacuum disco axle, so my front DS only turns in 4wd. I was not sure if there was any issue that would make spinning it at high speed any different from a non disco.

I mentioned that I have a SYE because if I didn't, someone would say 'The TC will puke fluid out the rear slip yoke if the DS is removed.

My other concern was heat. I know some people said they have driven in FWD for some time, but never mentioned their speeds. I wanted to check that at 70mph, the TC won't over heat in 4wd.

I should mention some other specs too:

6" lift
31's
NP231
D30 (disco)/D44
SYE/6* shims


The vibration I am trying to track down is a some sort of resonance I believe. Around 65-75mph, I get a vibration that feels like an 'up and down' shake.

I was concerned about using a 6 degree shim because it seems the most anyone uses is a 4 degree. However, I properly measured the slope/angles when calculating my necessary shim, and it called for a 6*. I seem to recall though that after the SYE install, but before the shim install, I didn't have any vibration. I want to narrow the vibes to the rear drivetrain by removing the DS and see if it disappears. If it doesn't, then I will look at the tires/wheels (which I just rebalanced this week)

I have made several long trips with just the front drive operating(8+hrs and 400 miles).It will handle differently,and I would not do any "jackrabbit" starts.It will not damage the TC as long as the fluid stays in the case.
Wayne

I have made several long trips with just the front drive operating(8+hrs and 400 miles).It will handle differently,and I would not do any "jackrabbit" starts.It will not damage the TC as long as the fluid stays in the case.
Wayne
This was at interstate speeds-

you'll be fine driving it normally; i daily drove it everywhere in FWD while the rear shaft was out for about a month

I just did the same thing with a lock right in the front.

Make sure your tire pressures are the same in each front tire.

Be prepared for the rig to want to change lanes on it's own when getting on or off the gas. I reached 80+ a few times and it was no biggie with equal tire pressure, but you still notice the left to right jerkiness.

10-4

Thanks for the advice everyone.