>when i get the gears done on my truck, i am going to put synthetic gear oil
>in the rear-end. i need to know what weight to get. in my manual there is
>nothing that specifies the type, however, in my Hayes manual, it says 75W90.
You've probably already been told this, but generally use the same
viscosity of synthetic oil as you would dino. For the same weight
however, the synth will appear thinner, will lube better, and will provide
better protection. As the others have said, run dino for at least 500-1000
miles for break-in before switching to synthetic.
As far as specs, 75W90 is basically the same as 80W90. The figures
represent 75 weight when cold, and 90 weight when warm (same for all API
rated oils, i.e. 10W30).
>so, what is the weight that i should use? i would like to use the Redline
gear oil, but should i go with Mobil 1 75W90 or Royal Purple 75W90? also,
the Redline already includes a "limited-slip friction modifier," does that
mean that i won't need to use an additional limited slip modifier?
I run RedLine 75W90 in all of my vehicles. It does have LSD friction
modifier in it already but some LSD units require more. I put it in my
factory Dakota trac-lok with no additional friction modifier and it has
been fine. My brother used it in his Auburn LSD however and had to add
about 2oz of modifier after a few weeks when everything got settled
in. The RedLine friction modifier is VERY potent, a little goes a long
way, just add 1oz at a time and test. When adding, the specs say to
perform at least 12 tight figure 8's or circles in each direction to
exercise the clutch packs and get fresh fluid between the clutches. In my
experience however, it took more like 20 to get started, and the fluid
doesn't fully flow around everything for a few weeks depending on where and
how you drive.
My Dak w/Mopar 8.25 rear-end took about 2.4 qts. of lube.
>in which case i would need 3, and what isn't used goes into my
tranny when i do a tranny fluid change).
I wouldn't use the same fluid for a manual tranny however as it contains
friction modifiers (specified by the API designation GL-5) that are
corrosive to the bronze and other alloys in your tranny (shifting parts,
synchro rings, etc.). I was given these instructions when I had my tranny
rebuilt from a very knowledgeable shop, and have heard it repeated numerous
times since. For the tranny, at least use gear lube w/o friction modifier
(GL-4 or lower), or get the specific RedLine manual tranny lube lube (MTL
or MT-90) which I have really liked in my vehicles. It's the same price as
the rear-end lube and I like to keep a little extra around anyway to top
off with.
Hope this helps. I'm a big RedLine fan, but any properly spec'd synthetic
oil is probably better than dino juice and is worth the $$ in the long run
if you plan to keep your car.
Kevin
Kevin Sellstrom, W6KTB E-Mail:ksellstr@softcom.net
***Wilton, California***
'99 Dodge Dakota CC, 4x4, 5.2,
'69 Dodge D200, 4x2, 318,
Also: '83 Volvo 244Ti, '85 Volvo 244, '68 Volvo 122S, '98 Specialized
Rockhopper A1FS
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