Speed vs RPM with 4.10 rearend

[Calvin 60]

I was wondering if any of you have a similar rig and do these Speed vs RPM with a 4.10 rearend sound about right?

55-1950
60-2150
65-2350

I am checking to make sure that my OD is working. I will be checking the MPG in the near future and will post my results.

[Randee of the Redwoods]

I can't speak for all the mph's, but I do know on mine, at about 57 I'm at 2000rpm. Just from that, I'd say your OD is working fine. I have 265/75/16's on my truck so there will be a slight descrepency. I think, don't hold me to this, at about 67, I'm taching about 2350rpm myself. That's as high as I go on the interstate for mileage concerns(4:10's will suck down some fuel), and it keeps me above the speed limit.

[GARY PAGE]

Sounds right

[S\W Off Road]

If you put larger tires on it then the 4.10's are great! When I'm at 75 mph my rpm's are at 2200 and that is with my VSSB set right for the 35" tires.

[Dvldog 8793]

sounds like the right stuff.

[Beedee]

one thing to remember with these things, the tach is run off the alternator so it is close but not the real rpm, if your off by a few rpm from the rest of us, no big deal.
I was just watching mine today, at 7o mph I was taching over about 2350.

[Scottpearce]

Calvin,

These are the approximate RPM's for the speeds you indicated with 235/85 R16 tires, and The VSSB corrected for proper speedometer accuracy. If you run tire sizes other than stock and don't correct your vssb, then your rpm's will match the stock tire speed, even though you are actually traveling another speed. Hope I didn't throw anyone with that [img]tongue.gif[/img]

55mph ---1800 rpm
60mph ---1950 rpm
65mph ---2125 rpm

When I had the 4.10's in my truck, my tach read 2600rpm at 65 mph! I have since gotten my tach reading alot closer to true, but it still reads about 5% high. Someday I'll turn the proper diameter pulley for the alternator to get it right on (+/- 1%)

-Scott

[Lug]

94 'burb K2500 with well worn 235/85R16. 2000 rpm 60 mph,2350rpm 70 mph. Mph was checked with a watch last night, planning on double checking today with a gps. The RPO code is worn off the sticker, but it looks like it is a 3.73 r&p. What is the o/d ratio of the automatic tranny? According to the mph/rpm calculator I have the tranny is close to 0.78 when it is in overdrive.
Justin

[Scottpearce]

94 'burb K2500 with well worn 235/85R16. 2000 rpm 60 mph,2350rpm 70 mph. Mph was checked with a watch last night, planning on double checking today with a gps. The RPO code is worn off the sticker, but it looks like it is a 3.73 r&p. What is the o/d ratio of the automatic tranny? According to the mph/rpm calculator I have the tranny is close to 0.78 when it is in overdrive.
Justin

Overdrive ratio of the 4L80E transmission is .75:1 An easy way to check the accuracy of your speedometer is to clock it against the mile markers that are along just about every major highway. Go ten mile markers and see how far off your odometer is, for every tenth of a mile you are off in a ten mile span, you have 1% error. In otherwords, if you clock 9.5 miles in the 10 mile span, then you are reading 5% low If your VSSB has been corrected for the 235/85 tires, then 4.10s would give you the readings you are seeing. 3.73's would be about 1800rpm @60mph and about 2100rpm @70mph 4.10's are about 2000rpm @60mph and 2300rpm @70mph

[CaseyR]

What are the RPO codes for 3.73 & 4.10?

[Tony J.]

I believe I saw in another thread- GT4 for the 3.73 and GT5 for the 4.10. I'm sure about the first and last character, just not the middle one.

[moondoggie]

Good Day!

My pickup turns 1750 rpm @ 70 mph. Oh, I'm sorry, I forgot: that's with my Gear Vendors engaged. Sorry, I didn't mean to make you all feel bad because you don't have a Gear Vendors. [img]tongue.gif[/img]

(≈ 2000 rpm @ 60 mph without GV, 4.10 gears, VSSB corrected for 235/85 tires.)

Blessings!

Brian Johnson, #5044

[Beedee]

Thats right Moondoggie, keep rubbing my nose in it . Makes me want to go out and spend a whole bunch a money .
Whats fuel worth in your part of the world???

[moondoggie]

Good Day!

$1.569, last fill.

Blessings!

Brian Johnson, #5044

[Beedee]

Hey Moondoggie
Up in my part of the world I paid $.649 a Liter so doing some quick calculations in my head that works out to around $2.56 for a US gallon.
I think you should send me you gear vendor as an international display of good will
PS, thanks for the info from some of the other posts [img]smile.gif[/img]

[moondoggie]

Good Day!

I thought I

[jcomp]

If you mosey over to 4Lo.com (clicky) you can use their calculator to compute your gear ratio or engine RPM or whatever. Pretty handy for those of us who are afraid of math.