Topic: Duals Grinding On Coast

[Jordan7118]

Here's my setup:

R151 turbo tranny
23 spline trubo crawl box
MC07-R10 23 spline adapter
Top shift 85 t-case with MC 4.7 gears

I took it out on the highway without the rear shaft (don't worry about it...) and the grinding wasn't there.

Then, I took it out again in 2HI and something grinds real bad in 4th gear on coast (clutch in). Sounds horrible.

I put it in 4LO and it doesn't make those noises.

I'm really confused. I think it's something in the rear case. Any ideas?

[79coyotefrg]

didnt you put these together ??  from what you say  it kinda sound like the rear diff

chock the tires, remove rear shaft and se if the pinion moves at all

[Hyena]

some people had there dual cases do this like i did.  my noise went away after awhile, this was like 4 years ago too.  i pulled them apart a couple montsh ago and found a bad bearing in the rear case. 

[Marlin]

What lift are you running?

Do you have a c/v joint on the rear driveshaft?
Super common problem to get noise on the coast or when you are "floating".

Is your pinion pointed at the rear flange of the t-case?
Is your drive shaft in time?

Removing the rear driveshaft and driving the truck will not tell you much, since you are now driving the front end only.

Check out your rear drive shaft, I think this is your problem.

[Jordan7118 [OP]]

My pinion is pointed at the t-case, or just slightly below it. I have the t-case up far enough to have a flatbelly with the MC-07 R10, so it's pretty far up there.

I'm running about 4inches of lift in the rear via F150 springs.

I built the rear drive shaft out of sch. 40 pipe and Toyota components. It was only out about +/-.010".

Would a CV make that much of a difference?

I agree that taking the driveshaft off doesn't solve much. I was just putting that out there in hopes that it would help diagnose my situation.

THANKS SO MUCH FOR YOUR HELP!!!!

[Rockcrawlintoy]

My pinion is pointed at the t-case, or just slightly below it. I have the t-case up far enough to have a flatbelly with the MC-07 R10, so it's pretty far up there.

THANKS SO MUCH FOR YOUR HELP!!!!

pinion shouldn't be pointed at the t case unless you have a cv

[Marlin]

Thanks for your quick response.

You must run a c/v joint.

Remember that without a c/v joint, the flanges but be within 2 degrees of being parall.
This means that in addition to obtaining a c/v joint, the output flange must also be changed because of the larger pattern.
When you run a c/v joint, there must be no angle at the pinion.

And also try to get the runout down to +/- 0.005.

Marlin 

[Jordan7118 [OP]]

I've got a CV for the rear. It's an IFS CV, so I have to do the clearance mod. I drilled the flange on the output with the u-joint pattern (it's a CV flange in case I had to run my front shaft in the rear (it's CV'd).

What would you recommend for driveshaft, then? I dunno if I can get it down to that tight of a tolerance. Would a drive shaft shop be able to use my materials and get it in balance? Never tried that approach before.

I'm glad it might be my driveshaft and not gears / t-cases. That's a load off my mind.

Again, thanks for your input!

[Rockcrawlintoy]

What would you recommend for driveshaft, then? I dunno if I can get it down to that tight of a tolerance. Would a drive shaft shop be able to use my materials and get it in balance? Never tried that approach before.

the driveline shop should be able to use your cv and slip and just retube the shaft do its longer

[Jordan7118 [OP]]

the driveline shop should be able to use your cv and slip and just retube the shaft do its longer

Could they get something thick enough for me? Should I check into that strange size DOM (2 7/8 by 3/16 or something?) ? I just don't wanna fight the on-street wobbles or have a shaft tear up off road. Maybe I should have an on-road and an offroad shaft? Dang't...