jv9999

The Dana 44 diff in my '87 gets loose and clunky when it heats up. I'm sure it's the diff. It's gets excessive backlash when hot, but it's right on spec when cold. Splines and axles are tight.
I've had it apart and took it to a local shop. Neither of us could find a problem with it on the bench. Just wondering if anyone has been here before?

Churchkey

Had a similar issue with a C3 IRS.
If it does not have gear whine during load or coast suggest investigating the posi.

SJW

Are you absolutely sure the problem's internal to the Dana? Tell us more about what leads you to think it is. Any chance it's hub spline lash at one of the wheels?

Live well,

SJW

jv9999

Fair question. Because I went through everything else. All 6 u-joints, new teflon washers, new wheel bearings, checked the stub axle spine play and the fit with the new wheel bearings. Everything is tight. I even went so far as the go through the 4+3 in front of it, it's all tight as well. It's fine when it's cold which makes it harder to troubleshoot.

SJW

Okay, sounds as though you've covered a lot of ground trying to isolate and fix this. Now tell us more about exactly how/when/where, and under what conditions, you're hearing something that's not right.

Live well,

SJW

81c3

All I can think of is the gear lube viscosity.... Is it correct?

jv9999

I appreciate the brain storming. It's full of Mobil 1 80/90 with a bottle of Kendall posi lube.
It's fine when it's cold, but when it warms up it clunks when doing things like lifting the pedal in gear. Sounds like every other diff I've had that was worn and loose. Also it whines a little when it's warmed up. Not enough that most people would notice, but it's there.

If you rotate a tire and hold the prop shaft there is very little play when it's cold. But when it's been driven a while, I can make it clunk just by turning a wheel back and forth (off the ground obviously). Something in there gets a lot of play when hot. By "hot" I mean operating temp. It doesn't overheat.
It has 63K on it as far as I know. Hard to be sure with these.

Churchkey

Both rear tires @ the same pressure:

Check tire circumference on both rears they need to be the same size. If one tire is smaller the posi overheats = a bang or clunk noise when lifting the throttle, shifting gears, rolling a corner etc. Basically any change in the way the diff is loaded = noise.

jv9999

It's a good thought, but they are new and matching.

SJW

I'd start by making absolutely certain the lash/clunk is occurring within the diff. Stethoscope it with a helper to rock the wheel back and forth, and pinpoint the location of the clunk. Visually watch for lash between the wheel and half shaft (check both sides), etc.

Live well,

SJW

RichS

How's the breakaway on the posi? With one wheel jacked up can you turn it easy or hard? When the clutches wear the clearance in the spiders grow, causing slop.