The 4.88 mega thread!!

^^this^^

 

got 21.5 doing 65 against a headwind. probably could have gotten 22 if it wasn't so windy.

honestly, even with stock tires the gains with 4.88's are well worth the trade off of maybe 1-2 mpg on the highway and really you'll only see that loss at 70mph+.

 

Hey what gear oil are you guys using with your 4.88's?

$28 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 or something else? Also, why if different?

 

Came across a set of 4.88’s front and rear w/mini install kits. what you guys paying for a setup like that?

 

https://eastcoastgearsupply.com/files/PDF Files/ecgs-gear-oil-recommendation1.pdf

 

Good stuff, thanks.

 

So instead of

$28 75w-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75w-90 Lucas Syn. I should run the first fill of oil with 85w-140 Lucas and then change it at 500-1000 miles back to the 75w-90 Lucas? I don’t tow heavy loads (not heavier than a drift boat)

Some have told me that running the 85w-140 will take some of the mpgs. Is that true?

 

One other question
(trying to get some edumucation, sorry)

Will running 4.88 (REM polished) gears highway driving and road trips over mountain passes cause too much heat in the diff?

Which is worse? Running stock gears and higher rpms or 4.88’s (if more heat) and better rpm balance?

 

The heavier oil is more tolerant than the 75-90 and will handle the break-in much better but if you are using REM gears its a bit moot. The heavier oil may impact mpgs but it's likely negligible, there is no metrics to support it.

So heat build up or too much heat is mostly associated to brand new gears. When they forge the gears, there are burs and imperfections that increase the friction and cause an increase in heat build up in the oil and thus breaks the oil down pretty fast. Over time (the break-in) the gears essentially polish themselves and remove the burs and points of friction and they begin to operate under normal conditions and the oil temp is maintained within normal operating conditions. Once this polishing is complete you should not have any heat issues or concerns.

Imagine the R&P teeth being like sandpaper with microscopic grit and rubbing together, this is your friction. Overtime the sandpaper breaks down and is smooth, no more friction.

If the gears are REM polished then those friction points and burs have already been removed and the gears will actually operate more efficiently and will also operate cooler than non-REM gears. REM polishing removes the grit.

 

Once the gears are broken in drive the truck as you normally would.

https://eastcoastgearsupply.com/ft-1479-new-gear-break-in-procedure.html

 

Gears with REM ordered. Woot!

 

Tech question for you guys, I'm running my truck on a 6" lift, 34" tires, single piece double cardan Tom woods drive shaft (drive shaft angle = diff angle, The drive shaft is 68.5" long and has a diameter of 4") and4.88 gears. I've got a vibration that feels like it's from the drive line between 45-50mph and anything over 82mph. I'm pretty sure what I'm feeling is the rpm limit of the drive shaft but I'm not savy enough with drive shafts to know for sure. Anyone in here a drive line guru that could shed some light for me?

 

Did you try a different pair of rims and tires that are known to be vibration free to rule that out as a possible cause? I’ve had big tires that are balanced out correctly but still throw a vibe when mounted.

 

I do t think its rims, but that could be it. I'm switching up my tire and wheel combo here soon so we will find out if that changes it

 

It may not be but it’s really hard to chase down a driveline vibration without eliminating as many possible sources as possible.
I’d hate to do trial and errors with shims and stuff trying to nail down the issue only to find out a weight flew off the rim or something else like that.
Right now you got 2 big factors that affect vibrations and those are rims/tires and suspension geometry. Take the rims/tires out of the equation and then you can concentrate on driveline angle.

 

No one likes trial and error like that haha
I got the new wheels and tires on, now it's just time to take it up to speed and see what happens.

It runs about 2k rpm doing 70. 315/70r17. Dont wanna talk about mileage any more, went from about 18mpg on 285/75r17 on the highway to what looks like 15ish. More trips will have to be made to know but I can definately feel the truck working harder to move thats tires.

 

I'm averaging about 13.5 so I have no sympathy for your 15 lol

 

Just did a road test above 80 and it still vibrates at the same speed. Dis notice more vibration on deceleration

 

I dont know how buy I will find a way to get 16 haha

 

So I would try a 2 degree shim to see what happens