Differential and tranny lube recommendations for '95 PSD?

[Bob A.]

I've tried several searches for differential and tranny lube recommendations for 7.3l PSDs and came up with nothing. Suggestions? I would like to go synthetic with the differentials (4X4). I have a ZF 5 speed manual tranny which is spec.'d for synthetic ATF.

Two reasons for these requests:

1. I'm going to be carrying a 9 and a half foot camper here shortly and would like to change to a synthetic differential fluid.

2. I'm currently running AMSOIL ATF in the tranny which has helped some with a second gear downshift problem when cold. This shifting problem started when I had to replace the two piece flywheel/clutch assembly. Unfortunately, I chose to go with an aftermarket, single piece flywheel/clutch. I don't think the new clutch is strong enough to handle well the PSD equipment. There were no tranny problems prior to the switch.

At this time I don't have the money to switch back to a two piece flywheel/clutch assembly, so am trying to maximize my truck's performance with the best lubes I can come up with.

As an aside, the Ford syn. ATF specified for the ZF manual transmission isn't nearly as good a performer as the AMSOIL, given the tranny issue I've got. Are there other synthetic ATFs that might work better? I know AMSOIL has come out with a couple of new tranny fluids in the last year or so. How about Royal Purple's Synchromax (I think that's the name of it). Any other ideas?

In short, what differential and tranny fluids would you recommend for my '95 PSD 4X4 with ZF 5 speed mannual tranny (specified for synthetic ATF)?

Thanks.

 

[Bob A.]

Thanks, TLR. Actually, I don't have a favorite. Maybe they're all good?!!? Probably. I just thought there might be some specific recommendation for the PSDs.

How about Schaeffer's? I wouldn't mind getting connected with their products. This might be a good way to do it.

Bob A.

 

[TheLoneRanger]

Bob, the rear diff oil is a no-brainer; go with a 75W140 synthetic only, in your favorite brand. This synthetic weight is factory fill on later model Ford truck diffs, and might be in yours already. This will give maximum protection.
(You can use 75W90 syn in the front diff, if you wish.)

I'll let more knowlegeable others hash out the trans' ATF suggestions.

TLR

 

[TheLoneRanger]

Bob, I think most specs for the 75W140 are the same, but there may be minor differences in brands. To tell the truth, I buy the syn Valvoline or Mobil 1 off the shelf of the local auto parts store.

I was hoping someone would chime in on the trans ATF suggestions. To me, it sounds like the clutch isn't disengaging enough, and dragging slightly. Can you adjust it? If it's hydraulic, maybe it has some air in the lines and needs bleeding.....?

 

[unDummy]

My vote if for any full synth 140wt gear oil for the 'ends.

And, I wouldn't use an ATF in a manual tranny.

For the manual tranny, use an MTF:
RoyalPurple Synchromax
SpecialtyFormulations MTFglide
Torco MTF

If you want to go a little thicker:
Pzl Synchromesh
RL MTL
SF SyncroGlide
Amsoil MTF

 

[Bob A.]

UnDummy,

Ford specifies a synthetic MTF for the ZF 5 speed transmission. After I changed to the single piece flywheel/clutch, Ford's product didn't work well at all. I sought all kinds of input about an alternative. AMSOIL was recommended to me by a local diesel engine mechanic. It has been working well, with the exception of downshifting into second gear. The transmission actually shifts smoother with the AMSOIL in all of the other gears than it did with Ford's synthetic "MTF", which, I believe, is made (or was several years back) by Conoco.

I agree with you about the clutch not doing something right with respect to the downshifting. I asked the mechanic who installed the flywheel/clutch about the possibility of adjusting the clutch. He said it doesn't adjust.

Whether that's right or not, I don't know.

I have close to 50,000 miles on this assembly. When I get another 50K on it, I'll probably pony up the bucks to go back to OEM engineered parts. The problem with that scenario is that Ford went to their own single piece assembly because they did have trouble with the dual format. Unfortunately, I was told that Ford's single piece design doesn't fit the '95 DIT, so I ended up with an aftermarket model that was touted as being a good product.

I doubt that any lube is going to make much difference, but hope springs eternal.

The fact is that the AMSOIL ATF performs significantly better than Ford's synthetic "MTF". I was hoping maybe someone might have an idea about or experience with other synthetic tran. fluids. I think Molakule has some products he's put together. I think I'll contact him directly.

But don't let this last statement deter anyone from posting suggestions. I'm all ears.

Thanks.
Bob A.