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Topic Review (Newest First)
05-08-2011 08:13 PM
rics1997 I running 285/70/17 MTR's (32.71") at 35psi (set computer to 31.75 to correct speed to GPS)

At 70 mph auto in O/D, with the new 4.88 Yukon gears, RPM's are around 2550
05-08-2011 08:12 PM
JIMBOX I figured that was the diff-you're reading a GPS and I'm lookin at the dash tach-no way to interpolate between the 500 rpm jumps !!


Quote:
Originally Posted by joe002 View Post
Yeah, you may want to check it with a GPS.

More Power!
It's a guesstimate !

JIMBO
05-08-2011 08:09 PM
GREEN-MACHINE thanks guys,, looks like i'll stick to my origanly plans 35's with 4.88.
05-08-2011 08:05 PM
joe002
Quote:
Originally Posted by JIMBOX View Post
Yea, I've recal'd the speedo, but I may be off the tire height, because of Desert temps and




It may have read 2650 rpm, as I was "PASSING THRUIT"

Heh Heh, hard to tell, but the amazing thing is the feeling of power, that was never there before and when you putit in "D"-O/D-thats where it stays-doesn't downshift, even for hills--KEWL

JIMBO
Yeah, you may want to check it with a GPS.

More Power!
05-08-2011 08:00 PM
JIMBOX Yea, I've recal'd the speedo, but I may be off the tire height, because of Desert temps and


Quote:
Originally Posted by joe002 View Post
Did you already recalibrate your speedo and gears with your ProCal? I would have thought you would be higher than that...
It may have read 2650 rpm, as I was "PASSING THRUIT"

Heh Heh, hard to tell, but the amazing thing is the feeling of power, that was never there before and when you putit in "D"-O/D-thats where it stays-doesn't downshift, even for hills--KEWL

JIMBO
05-08-2011 07:49 PM
joe002
Quote:
Originally Posted by JIMBOX View Post
Heh heh, we're all within 100 rpm--




I've got LT295/75x16 Hankook Dynapro MTs and they're 33.2" at 30 psi--2600 rpm at 70-O/D

:rofl JIMBO
Did you already recalibrate your speedo and gears with your ProCal? I would have thought you would be higher than that...
05-08-2011 07:35 PM
JIMBOX Heh heh, we're all within 100 rpm--


Quote:
Originally Posted by GREEN-MACHINE View Post
jimbox, was wondering what size tires and what rpm at 70 mph,, if i missed it one of your post, im sorry
I've got LT295/75x16 Hankook Dynapro MTs and they're 33.2" at 30 psi--2600 rpm at 70-O/D

:rofl JIMBO
05-08-2011 07:26 PM
joe002
Quote:
Originally Posted by GREEN-MACHINE View Post
jimbox, was wondering what size tires and what rpm at 70 mph,, if i missed it one of your post, im sorry

FYI - my data point as Jim has different tires then me - I'm running KM2 35s with 5.38s and am at 2,550 at 70 mph with O/D On.
05-08-2011 07:20 PM
GREEN-MACHINE jimbox, was wondering what size tires and what rpm at 70 mph,, if i missed it one of your post, im sorry
05-08-2011 04:06 PM
joe002
Quote:
Originally Posted by baytownbert View Post
Are y'all using a heat gun to read these diff temps, or sticking a thermometer in the plug hole?
Im using an IR gun - I use it to work on the A/C in my house.
05-08-2011 04:00 PM
JIMBOX Na, I don't have an infrared thermo, so I'm using a digital "contact" thermo, measured at the Shielded bottom of the pumpkin, where the oil sits-


Quote:
Originally Posted by baytownbert View Post
Are y'all using a heat gun to read these diff temps, or sticking a thermometer in the plug hole?
It drops temp FAST, but also rises FAST-

Tonsafun !

JIMBO
05-08-2011 03:56 PM
JIMBOX Hell, I'm spending a lot more for gas than I have for oil/grease-breaking these things in !!


Quote:
Originally Posted by joe002 View Post
Guess since I saw 185F at 102F ambient I'm broken in good. I do remember the temps coming down, but unfortunately I seem to have lost my record sheet.



Yeah, I've done a little research on gear oil, and you want to look for an oil that specifies that it meets or exceeds (not simply recommended for, or can be used with, etc.) API GL-5 (easy to do), and MT-1 and SAE J2360 (harder to find). Valvoline 75w-90 Synthetic does.
The front diff, doesn't get any wear (relatively) because it's being "worn" bassackward--IE: the ring is wearing the pinion, instead of visyversy-

They told me to get a couple hundred miles onem then do some light "LEVL" 4wd (4hi) to "assist" the front diff breakin---soon

You're right if your at 185 "normal", ops--thats GOODO !!

JIMBO
05-08-2011 03:51 PM
baytownbert Are y'all using a heat gun to read these diff temps, or sticking a thermometer in the plug hole?
05-08-2011 03:41 PM
joe002
Quote:
Originally Posted by JIMBOX View Post
and about 200F "normAL" ops for the "BROKEIN" diff...
Guess since I saw 185F at 102F ambient I'm broken in good. I do remember the temps coming down, but unfortunately I seem to have lost my record sheet.


Quote:
Originally Posted by JIMBOX View Post
...to maintain their warranty, to use Valvoline syn ...

Yeah, I've done a little research on gear oil, and you want to look for an oil that specifies that it meets or exceeds (not simply recommended for, or can be used with, etc.) API GL-5 (easy to do), and MT-1 and SAE J2360 (harder to find). Valvoline 75w-90 Synthetic does.
05-08-2011 03:12 PM
JIMBOX I don't blame you for thinking AMSOIL-they're right at the top synthetic and I would use them, but


Quote:
Originally Posted by baytownbert View Post
I'm wondering about Amsoil (or equiv) temps in the pumpkins over dino oils. Which are you running, or do you plan to run?
I had been using Mobile 1 75W-140 and YUKON/ORI (Reno) said, to maintain their warranty, to use Valvoline syn -

They have Valvoline "severe" 75W-90 syn in there, along with an abrasive/polymer additive, for heat and molecular changes, untill my 500 miles and they have agreed for me to replace it with Valvoline 75W-140 ext. syn--

So dat don't leave me with much choice !!

I've also been told to use the latest Valvoline Palladium-multi-purpose HD/HT grease for the Synergy Ball Joints-

Damn jeeps costing some money !!

JIMBO
05-08-2011 02:56 PM
baytownbert I'm wondering about Amsoil (or equiv) temps in the pumpkins over dino oils. Which are you running, or do you plan to run?
05-08-2011 12:19 PM
JIMBOX Yea, thanx joe-


Quote:
Originally Posted by joe002 View Post
Looking good.

I wrote down all of my front/rear diff temps when I was breaking it in, but I cant find it now.

I measured my rear yesterday after driving on the freeway with the ambient temp at 102 I was 185. Im still shopping around for my auto temp.
Amsoil has studies of field/lab/dyno tests and has recorded 370F "breakin" temps-under load and 230 was the avg op temp for the rear diff-"breakin" temps under "normal" ops and about 200F "normAL" ops for the "BROKEIN" diff. !!

JIMBO
05-08-2011 12:09 PM
joe002 Looking good.

I wrote down all of my front/rear diff temps when I was breaking it in, but I cant find it now.

I measured my rear yesterday after driving on the freeway with the ambient temp at 102 I was 185. Im still shopping around for my auto temp.
05-08-2011 12:01 PM
JIMBOX
Last 5.38/ diff. gear update

Well, it should be the last-

I've maintained a strict 20/40 mile runs/w 1 hr cooldown and now I'm almost halfway thru the 500 mile breakin edict, from YUKON-

Just filled up at 10,551 miles, after 40 mile run at 25/35/45 and 65 mph, 189.7 miles---took 11.32 gals ( tank), for avg of 16.93 mpg

Front diff-cool/rear diff at 251 F and auto tranny steady at 135 for the duration

Keepyerpowderdry-

JIMBO

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