Topic: 4.88 and 5.29 Rigs: Requesting RPM at 70MPH

[BigMike]

I am about to setup my truck with 4.88s with my 33s and later plan on running either 36s or 37s.

I want to keep my RPM below 3k at 70MPH. 2,850rpm @ 70mph would be idea. I often drive at 75MPH, so if that could be right at 3,000 then it would be perfect.

I've used our tire/rpm calculator, but its not accurate and I dont know the math for tire expansion or anything so I dont want to calculate it, I want some real world numbers.

So here is my question: Im thinking about using 4.88s with 36s but Im afraid the rpm will be to low, like 2500 @ 70.

Right now I am 3.9:1 stock on my 33s, and I am about 2400rpm at 70MPH and at the speed Ive really gotta step into it to, especially if I slow down to 60 or 65, I'll downshift to 4th. Once I get it up to 80mph, then its ok because its 2800-something but of course Im not going to drive around all day like that..

We had a truck at the shop that had 35s with 4.88s and the rpm at 70 was just shy of 3k, which I thought was PERFECT, BUT! Dave told me today that the rig had 33s. So, thats great if I stay with my 33s but of course that would be awful with 37s..

Here's what my calculator I wrote is telling me @ about 70MPH:

	3.90:1	4.11:1	4.88:1	5.29:1
33s	2,360	2,490	2,960	3,210
35s	2,230	2,350	2,790	3,025
36s	2,170	2,285	2,715	2,940
37s	2,110	2,225	2,640	2,860

So it looks like 5.29s would be the best since I plan on running 36s or 37s, but I just figured that for now since Ive got 33s, I would just go 4.88 and then keep them when I get some 36/37s.

So I guess what I really want to know is how 4.88:1 on 36s/37s is at 70 MPH - in the real world. I can calculate the numbers, but I think they are not accurate

Thanks
BigMike

[BLACKDOG]

Dont know if you really care or if it helps, but my your calculations may not be too far off.  Off the top of my head, I think my 5.29s run right under 3K at 70, mabye a little bit less.  When I go home from work, I'll look at it and let you know for sure

[CTENG in KS]

my 35's and 5.29's put me around 3,000 at 70.  I would say go 5.29's, you will cruise no problems, still have some power in 5th, and your mileage will be reasonable.

[BLACKDOG]

Yeah, kinda what I am thinking too.  That 3k at 70 sounds about right, but you are SOL for me checking it today.  I get off in the middle of rush hour.  I'll be lucky to be going 7 let alone 70.

[blyota91]

Don't you also have to take into account the gear ratio for 5th to make this come out correct?

[79coyotefrg]

mike,  dont forget 5.29's with your 5th is 4.44 final drive,  3000rpm + 36 inchers + 4.44 = 72mph

[79coyotefrg]

drop to 4th and you'll be kicking around 3600

[trailtoy]

Definitely go 5.29.  I'm running 4.88's on 35's and it's a dog on hills.  I think the speed calculator is pretty accurate.  Just remember to calculate for 5th gear.

[kyle_22r]

i'm gonna step outside the box on this one and say run 4.56s.  you have more than enough power to turn 33s with 4.56 gears, much more than most any 20R/22R/22RE will ever see.

[reklund5]

Mike-

My 37" MTR's and 5.29's run at like 3200 in 4th gear at 70.  My tired old 22R block just cant sustain 70 in 5th, even with the EFI conversion, TRD cam and header...

I'd think with the stronger 3RZ you've got you'd be right on with 5.29's in 5th gear.  I know you have plans to run tripple cases and 4.88's but your highway cruising RPM might be just a tad lower than what you're shooting for...or you could just run in 4th on the highway...
 
I just had to drive my truck 3hrs each way to Farmington last weekend to go wheeling, and my 37's run down the road smooth as glass at about 68, and I have NO weights on  my wheels, no balancing whatsoever. 

Also, my speedo reads about 6mph too slow with 5.29's and 37's.  I haven't played around with changing the drive gear any, as I just use my GPS most of the time, but you CAN just change the gear on the speedo drive (if its a gear driven cable).  I seem to remember you having an electric speed sensor, in which case JET mfg. makes a correction box that you wire in-line between your sensor and ECU.


HTH,
Ryan

[TacoRunner]

Drop in the 5.29's and the 35's now. and start trimming the fenders when they start rubbing then you never have worry about have the wrong gear.   Plus your calculator should tell you that 5.29's are perfect for 37's   35's will get you around 2900 RPM's with 5.29's          4.88's are great gears but I would not go more that a 35, maybe a 36 with them unless you do some power adders.  I have your motor in my 85 4runner with 5.29's and 35's its nice but a little high on the freeway.

[toyhatsu]

BigMike,

Using your calculator I end up with 4100 rpm's with 33's and 5.71's and 3800 rpm's with 35's for 70mph.  Is my first gear going to be worthless on the street...start in second gear?  What does the 3RZ redline at?  Thanks...

[BigMike [OP]]

Thanks for all of these terrific replys guys

This is just what I was looking for. With your suggestions, I've decided to run 5.29s. For now I only have 33s, so I will just use 5.29s and my 33s.

And my calculations in my opening post was in fifth gear, which in my W56 is 0.85:1.

kyle, I thought about trying 4.56s, but since I am installing an electric locker = V6 gear set, no one makes that ratio for me. Also I will use a high pinion in the front some day, so both diffs are not available as 4.56....

I know my calculations are reasonable, but they do not match what my truck actually does. So, I am betting Marlin that someone has pulled the 3.90s and swapped in some 4.11s into my truck. Marlin thinks that's :bull crap: and he's betting me that its got the stock 3.9s. If I do the calculations as 3.90, then the calculator doesnt match my vehicle, but if I do it as 4.11s, it matches, but this could just be a lucky matching number if my calculator is not accurate at all...

Toyhatsu, the 3RZ has the same redline as my 22R tach, I think 5600? I've been there a couple of times already

[79coyotefrg]

mike  what does your info tag say your axle code is,  G292= 4.10 G072=3.90 G102=4.37

[79coyotefrg]

using you calc and my general math skill,  you do have 4.10's, im figuring 32.5 for those 33's

[79coyotefrg]

check your speed and rpm in 4th ,  and remember  to use 1.1:1,  not 1:1

[brainlessfool]

So mikey, is the overdrive in your w56 the same as in my L52? ratio wise? 

[79coyotefrg]

So mikey, is the overdrive in your w56 the same as in my L52? ratio wise?

yep  the same .85:1

[BigMike [OP]]

check your speed and rpm in 4th , and remember to use 1.1:1, not 1:1

Why 1.1? 4th is one to one..

I'll check my axle code today....

[79coyotefrg]

i kept coming up with the wrong numbers till i found a old toyota manual  and it said 1.1:1   then i ran the numbers and everything came out right

[79coyotefrg]

hey mike you should grab Hyena's axles with the 5.29's he has for sale

[Bob Garrett]

kyle, I thought about trying 4.56s, but since I am installing an electric locker = V6 gear set, no one makes that ratio for me. Also I will use a high pinion in the front some day, so both diffs are not available as 4.56....

Actually, 4:56 is available for the HP diff. That's what I have in my 80 series LC.

Bob