Team420

Cyl 1: 175 cyl 2: 176
Cyl 3: 170 cyl 4: 165
cyl 5: 170 cyl 6: 175

Yup there they are, I didnt bother to check cyl 6 because I obviously have problems any way, plus..as every one knows, cyl 6 is a pita to get to. I suspect a faulty h/g, I do not have any serious tap or knock, never burns oil, it does loose coolant, but not in the oil, and vice versa, I have never overheated my truck, however, 1 day on the highway this winter( and it was real cold out) the truck started running hot, I pulled over to let it cool down, then drove the rest of the way home (80 mi) with no problems...or ever since then. Questions, comments...advice??
btw... I have a whole other motor waiting in my garage...it only has 130 k on it... would it be easier/ more sensible to replace my h/g's... or swap the motor and possibly have this problem with the new motor in the future... I am leaning toward the swap cuz it will be easier to fix my motor while out of the truck.

toytech76

swapping the motor at 130K? Thats a huge expense and not needed at all. Pull the heads, have them checked at the machine shop and have them do a proper valve grind while they are off. Slap it back together and run it. I noticed your sig, 4.88 gears with 31" tires? Your eng doesnt need those gears for those tires. Over revving your eng IMO

Team420

my rig has 255k on it...the donor motor has 130k... 4,88 is what came stock with the truck...however i am switching to 4.10 after I get this deal worked out. o...and I am actually running 235's currently.

toytech76

Ive never seen stock 4.88's. Have you had the truck since new? I would go with the 4.10's with 235's and 4.56's with the 31's. I still wouldnt worry about 130k on your motor. Just take care of the top end

mt_goat

That's the factory Toyota gearing for the 3.0/auto tranny with the 31" tire package. No, it's not too low, if anything its geared too high for the 150 hp 3.slo. That OD gear is a monster (like .71:1 IIRC) The truck would go 120 mph in that gear before it redlines, that is of course if it had the power to pull the gear, which it doesn't.

Marc

What problems are you talking about?

Your compression results for the 5 cylinders you checked are good.

Crawdad

Yeah seriously, those compression numbers are actually pretty good. There's a little more variation from 165 to 175 than I would want, but it ain't exactly a new motor. That's strong.

Workhorse

I don't see anything wrong with the compression readings either but it is the morning AFTER memorial day weekend..

mt_goat

I concur. Its a shame you didn't test the 6th one too.

Team420

ya...I suspect cyl 6 is prob even worse...gonna try to check tonight... and the drop of 11 between 2cyl and 4cyl...thats a little more than I want... I know it is still strong...but i am def loosing coolant... just went out to check a few min ago and was down 1/2 gal....in 2 weeks...that is why I suspect the H/g... and I would prefer to fix it before it lets go...but I guess ill wait and see what cyl 6 brings...who knows maybe its @ 175?...and yes I am sure those are the factory gears...and as I said...Im going to 4.10 very soon....but I am willing to bet I loose mpg's because its gonna have to work harder to get up to speed...and I have no interest in doing 100mph...I rarely go over 70 in this truck.

zlathim

Thats my opinion as well. Check #6 to be certain, but I am only seeing about 6% difference between high & low.

mt_goat

4.10s? Why??? 4.88s are good. If anything, I'd go to 5.29s with a 31" tire and the 3.slo/auto. 4.10s would be ok if you go to about a 26" tire.

Red_Chili

What the.... Cylinder #6 is worse than.... perfect???

BEFORE you go to the trouble to swap motors and rebuild yours, have the cylinder scoped. If you have a clean piston top, you have a failing HG. If not... check for a pinhole leak in your radiator. You can find that by pressure testing your coolant system.

You really do not want to gear taller than the factory 4.88s... you really don't... 4.10s will ruin your day.

CJM

You cant swap your gears, those years 4Runners with the 4.88 package used special gearing, you cannot swap with any other toyota gears AFAIK.

mt_goat

Yeah that's true on the rear, you have to swap the whole 3rd member out. Rear 3rds are easy to find though.

mt_goat

Best thing to do would be to leave the factory 4.88s in there. If you want to change to a different ratio, remove the whole 3rd and sell it already setup, with the factory gear setup its worth more. For example: https://www.yotatech.com/forums/f11/wtb-4-88-s-146068/ Then put in a 3rd, professionally setup by Zuk, with the ratio and locker of your choice. http://www.gearinstalls.com/

Crawdad

I would sure as crap keep those 4.88 gears, too. You are definitely NOT over-revving your engine with the difference between 4.88 and 4.10. Keep them, because you'll want it when/if you step up to larger tires.

Think of it this way: in overdrive, at 70mph you are only turning 2500rpms with 4.88s and 31" tires. Even with 29" tires you are still only turning 2700rpms.

Now, with 4.10s and 31" tires, you are running roughly 2200rpm. Those extra 3-400 RPMS are not hurting a thing, and are only making a tiny impact on your gas mileage. I would even venture that going to 4.10s will hurt your gas mileage from the extra pedal you're going to have to give it to get up to the same speed.

And on those cylinder compression numbers, you are running with less than 10% variation between compression readings. That is strong, that is good, and that is not the source of your problems (unless cylinder 6 is completely hosed).

Team420

ok...sorry....checked it out, and the new gears I am installing are 4.56... they came out of the same truck my new motor and tranny came out of... I am swapping because my 3rd is a frankendiff... I parted it together from 3 junk diffs 3rd's to make 1 good one (lost driveshaft on highway @ 85mph), and it is ready to go..I know they say you cant do that or you will be replacing it within a couple k...but I did this at 190k and my rig now has 255k...so I must have done something right...any way...I already have this 4.56 3rd, and its in great working cond...so free beats $250+ for a new/used 4.88 3rd. I have not done the compression test on # 6 cyl yet...hope to get to it by the end of the day...but another reason I believ its the h/g is that I DO get white smoke on startup untill fully warmed, and I know that even with the compression #'s that I have it is still possible to have a bad h/g... seems to seal itself when warm..and from what I understand...this is a common sign that the h/g's are FAILING...not that they are already junk...but going to be eventually and I would just like to get it taken care of before it becomes a major problem and does damage to the lower end. I am listening to you guys tho, and I agree that it would prob be easier than to repair mine than swap the motor... but again..what does it cost to have heads shaved and cleaned up? I already have a motor, and I believe everything I need to do the swap... If someone could give me an approx price for both..so I could make a better decision... I would appriciate it.
btw...sorry for the long post!

zlathim

I was recently schooled on the use of Block Chek. You might want to try that stuff (but be sure to do it right) before you teardown the engine.

Team420

finally got the compression off #6cyl..... 175...ha...I expected it to be down around 150...guess i will not be tearing her down just yet...I will test the cooling system next. What could be causing the # 4 cyl to be so low? sticking valve maybe? also... I am almost positive I have a vacuum leak... been getting code 71 much more frequently...could that have anything to do with the lower compression in # 4 cyl?