Everyone with a T5 should download this manual:  www.tremec.com/anexos/TRSM-T5-0510-R1_173.pdf

The Tremec manual explains that the T5 uses Dextron II transmission fluid because the T5 uses needle bearings which need the lower viscosity lube to properly flow between the needle bearing rollers. Also, if you are using it in a manual transmission, the lube is manual transmission lube. If you use regular gear lube in a T5 the bearings will have a very short life.

If you are using a non-roller lifter camshaft you will have to provide proper lubrication, which means zinc and phosphorous in the form of ZDDP (zinc dithiophosphate). In the U.S. most manufacturers have quit adding zinc and phosphate because roller cams do not need them. We have to go to specialty oil suppliers like Amsoil, Royal Purple, and Joe Gibbs to get hot rod oil with these additives included. All the auto parts stores sell the ZDDP additive separately to be added to cheaper zinc and phosphate free oil.

You will have to use oil with the zink and phosphate additives both during break in and during normal driving. Without these lubricating additives, the lifters can weld themselves to the camshaft lobes.

With a freshly rebuilt engine I would use 5W-30

Hornman wrote:

Everyone with a T5 should download this manual:  www.tremec.com/anexos/TRSM-T5-0510-R1_173.pdf

The Tremec manual explains that the T5 uses Dextron II transmission fluid because the T5 uses needle bearings which need the lower viscosity lube to properly flow between the needle bearing rollers. Also, if you are using it in a manual transmission, the lube is manual transmission lube. If you use regular gear lube in a T5 the bearings will have a very short life.

If you are using a non-roller lifter camshaft you will have to provide proper lubrication, which means zinc and phosphorous in the form of ZDDP (zinc dithiophosphate). In the U.S. most manufacturers have quit adding zinc and phosphate because roller cams do not need them. We have to go to specialty oil suppliers like Amsoil, Royal Purple, and Joe Gibbs to get hot rod oil with these additives included. All the auto parts stores sell the ZDDP additive separately to be added to cheaper zinc and phosphate free oil.

You will have to use oil with the zink and phosphate additives both during break in and during normal driving. Without these lubricating additives, the lifters can weld themselves to the camshaft lobes.

With a freshly rebuilt engine I would use 5W-30

 
Thank you for teach me but there is something that still not clear about trans oil .
I havent say that is a t5 cobra z spec ( i dont know if change something about oil )
About Dextron i have found that is no longer available  . This is copy from MDL

The original Ford/Borg-Warner recommendation back in 1984 was Dextron II.  As this is no longer available, we and TREMEC recommend the 50 wt gear oil.)
Sayd that  50 wt gear oil dont mean nothing to me  .
The link you gave me refers only at dextron 2 .
Thanks !

for T5

https://www.amsoil.com/shop/by-product/transmission-fluid/automatic/signature-series-multi-vehicle-synthetic-automatic-transmission-fluid/?code=ATFQT-EA  

Alessandro wrote:

Thanks Don !
If i found amsoil z rod i have to add the zinc additive for break in ? Or this oil i enough for break in and regular use ?

z rod is all you need
 

In a T5 run either the lowest grade Dextron/Mercon auto tranny fluid you can find (either III or IV).  Or, run a quality synthetic auto tranny oil like Amsoil. 

Do not under any circumstance put a heavy weight gear oil in a WC T5; it will destroy it in short order.  The WC T5 has several tiny passages oil must flow through to properly lubricate everything.  Gear oil cannot flow through these passages, and the results are not pretty.

What cam are you using in the engine?  If its a roller cam the concern over zinc is overblown.  A flat tappet cam absolutely needs that zinc, but the reason the zinc was deemed able to be removed was because most of the US fleet at this point runs roller cams, which started being used in the late '80s.  The zinc was in the oil as an extreme pressure additive, which prevented wear at the interface of metal parts under considerable force (like the lifter/cam interface in a flat tappet engine).  In a roller cam engine that interface is constantly moving due to the roller, so the amount of pressure present is very much less, thus the lower zinc levels being okay for use in roller cammed engines. 

To break an engine in, NEVER use synthetic oil.  The rings won't ever seat with it.  A good conventional oil, or specially formulated break in oil is best.  After you get it to 10,000 miles go ahead and switch over to synthetic if you want.  Synthetic has a ton of benefits, but its actually too good to work as a break in oil.  Yes, I know that most new cars come with it from the factory, so how do they do that?  I'm told a very specific honing process on the bores, but no one knows exactly what it is, and thus synthetic may be fine for OEM engines at break in, but anything one of us rebuilt need to use conventional. 

For TKO . The engine is oem 289 with flat tappet . I will do break in with mineral oil with zddplus additive . Or if i can find amsoil but is difficult .  Thanks for tips !

Alessandro wrote:

For TKO . The engine is oem 289 with flat tappet . I will do break in with mineral oil with zddplus additive . Or if i can find amsoil but is difficult . Thanks for tips !

Amsoil is synthetic oil, good for the trans, not the engine.  Once the engine is broken in Amsoil is great.  I'm not sure what their distribution is internationally, but you can check their website here:

https://www.amsoil.com/

Its pricey oil, but I've had great results with it.  Run in my WRX for 180,000 miles changing at 8,000 with their filter.  Pulled the engine apart about 10,000 miles ago to fix damage from a broken timing belt idler pulley.  No appreciable wear on anything inside.  No ridge in the cylinders, cams and buckets all looked great, really impressive. 

http://www.enginebuildermag.com/2014/10/break-in-oils-and-assembly-lube-needs/

Don wrote:

http://www.enginebuildermag.com/2014/10/break-in-oils-and-assembly-lube-needs/

One point to be careful on here is that there is a note on using Diesel oil because it contains a higher concentration of ZDDP.  While that was true in 2014 its no longer the case.  The ZDDP has also been cut way back in Diesel oils too. 

Last edited by TKOPerformance (11/14/2017 11:17 AM)

  The ZDDP has also been cut way back in Diesel oils too. 
please could say in another way ? i dont understand it ...

The amsoil is sold in germany but is ( crazy price )   170 usd for 6 quart ... 28 $ each is too much ! . is like gold ! 

Also other brand like penn or spectro are not easy to find here .

So i have found Motul oil 20 w50 mineral base , made for old cars , before 1970  , then i will add zddplus zinc additive .