Dmf rattling like an smf

Just finished zf 5 swap into my 85 at 2 am this morning. It's awesome I love it! One little problem it grinds in neitral and somewhat when really lugging it. Symptoms are just like a smf. Only problem is that 2\3 of us that did thee project are sure it was a dual mass flywheel. Any thoughts?

If it’s a dmf and it’s rattling like a smf, it’s probably in need of replacement

If it’s gear rollover noise it will stop when you shove the clutch in. If it’s the DMF coming apart it’s usually will rattle regardless and especially when you shut it down.

yeah... if it's a dmf, get a LuK smf to replace it. The dmfs suck, even when they work "right" - had slipping, thought 8t was the clutch, turns out that dmfs have a second clutch surface inside that can slip.
Actually... both my dmf trucks failed that way - slipping due to the "torque limiter" clutch.

With new SMFs in both... much better, if slightly noisier.

It is a luk smf. Found that out for certain. I'm now running some synthetic 80 weight stuff. Our ranch mechanic who had serviced the donor truck previously thought that he had used the 80 weight previously and we both know for sure that the zf5 was quiet when it was in the donor truck. Put 4 quarts in and it ran quiet....... Until I got back from town and pulled into the shop. At that point the noise had returned.

My thought is that I might need to fill just a hair more and that when its cold it is quiet. Any thoughts? Thanks for your responses!!

O for for to mention noise does go away when clutch is pushed in

The zf5 takes auto trans fluid, I can't remember the type but you must use auto transfluid because it will not function properly. I'm not sure the symptoms of what happens when you use gear oil instead but I know they take atf

JAKRANCH said:

I'm now running some synthetic 80 weight stuff.

Click to expand...

:***:

No.... just.... no.....
Drain it before it grenades, you now need to completely flush out the trans.
ATF or Syn 10-30 (IIRC, might be straight 30wt, I don't run a ZF)

Get that gear oil out asap!

I’ve seen so many junk trans because of gear oil. It’s too thick. It’ll heat the bearings and burn up the synchros

Hmmm that's weird as far as I know all my dads farm trucks have been maintained this way for years and he's almost always had at least one 7.3 idi on the place. Would there be a difference on the low average speed farm truck? Granted we do lots of deep mudding with hay on the back?

I doubt it. The main problem with the gear oil is it’s too thick for the synchros. It doesn’t allow them to spin up efficiently and causes premature wear

So, I'd recomend ATF, that's what it's supposed to have.

I found 30w(I think) oil in my '93 when I bought it... probably to quiet down a noisy bearing. It worked fine cold(a little stiff perhaps), quieted it down... get it hot and it makes noise.

I decided to try gear oil... cold, it barely wanted to shift, wanted to grind etc. Once warmed up, it was great.

Swapped with Amsoil ATF, and while it was a little noisier, but shifts much better.

edit:
I will point out, just for reference, that I have a pretty worn transmission I picked up from the local wrecking yard for $170-ish. Turns out that what fluid came out of it was gray and full of little metal bits.
I'm currently running 4 quarts of Lucas Universal Transmission/Hydraulic fluid(close to 5w30 in thickness) and 1 quart of ATF in there, hoping to have something a /little/ thicker than straight ATF considering all the wear. It is working fine, but it's definitely got some bearing noises. Shifts fine cold, which is important.
I'm not going to /recommend/ it, though.

Slightly off topic... But I saw a 4L60 once with gear oil in it. It literally destroyed the ENTIRE transmission. Proper fluid is vital for tranny functionality and life span.

Which disc is in it? I had a real noisy Sachs SMF with a HD disc. Swapped for a standard disc and all is well.
In the pics 10 springs in the disc is standard disc. 8 springs is the HD.