I have an SM465 in my YJ and was wondering if in a stock vehicle equipped with a 4 speed with granny low, do you normally use 1st gear to start in? Or is it truely a 3 speed, but has the granny gear there for emergency use?

With the 3.07 gears, I have no problem starting off in 1st (granny) gear and holding 80-90 at highways speeds turning like 2500 rpms. Buzzes along at 75 turning like 2200. I get decent gas milage considering I'm pushing a brick through the wind and I'm up on 35" BFG's. I get roughly 15-16 MPG.

Am I harming anything starting off in 1st (granny) gear, or should I start looking to re-gear or at least put the 3.73 geared axles in that I've got on the trailer. This is my daily driver, also, so 4.56's are out of the question.... I need at least 12 MPG.

Matt

Normally you wouldn't use granny for starting off.It is designed to be for towing or slow going in rough terrain.As you probally noticed you need to almost need to come to a stop to get into granny,this is because it is not synchroed.I don't think it will hurt the trans.But I would look into regearing.I would go down to atleast 4.10s.You will find you have more power to pull the 35s and will beable to start off in 1st and save granny for wheeling.I have the 465 and 36"ers and 4.10s.I run 75 at just under 3000 rpm.And I get around 12 to 14 mpg.This is in a blazer with a 305.Blazin:rasta:

sounds to me like blazin is right on the money!
;)

Your not hurting anything and that 465 is the only reason your able to do it. I agree that you might want to go up some in gears. You would be amazed at that granny in the 465 is you had 4.10's You could creep along at about 2000 rpm and go about 3mph if you regeared. Then you would start is second and not have to shift so much. Getting into granny on them is sometimes is a challange.

If you already have the 3.73's waiting to go in........ I'd just put those in, and drive it like a three speed. If you're grinding coming out of granny on the upshift, just double clutch, and you should be fine. Also, if it kills your mileage going to the 3.73's just slow down a few MPH and you'll be fixed right up.

MT

Originally posted by ManglerYJ
Am I harming anything starting off in 1st (granny) gear, or should I start looking to re-gear or at least put the 3.73 geared axles in that I've got on the trailer. This is my daily driver, also, so 4.56's are out of the question.... I need at least 12 MPG.

Matt
Just to add a comment about gearing and mileage - it is a popular mis-conception that tall/overdrive gearing improves MPG - you still need the same amount of energy to propell the vehicle. All an overdrive effect does is lower RPM's on the freeway - in of itself that does not improve MPG - it improves efficiency by lowering engine RPM (friction).

As a case in point - my buddy went from 3.73's to 4.56's - he had put bigger tires on and his performance went downhill (poor around town and on hills - yes it cut freeway RPM's) He has seen his mileage actually increase aftyer changing the diff ratio because the rig was not being used in it's optimum power band.

So by changing to 3.73's you will not necessarily see a change in MPG. And, yes - the 465 is designed to start off in 2nd - the 1st, or more acurately granny low, is for towing, etc.

Depends on your engine. I am running a 465/205 set-up behind a Cad 500. I've got 35" tires and 3.07 gears. I usually start in 2nd. I get 15 mpg only when I run 70 mph. The Cad engine likes to pull against tall gears, just a function of how it was designed. Typically, you get your best mpg when your r.p.m.s are in the peak of your torque band. I consider 4th gear an overdrive. I can run 3rd from 20-60 mph. I sure miss my T-19 (Scout). Being able to downshift into 1st on a roll is a luxury. Anyway, when I hook my little half ton up to my 40' 5th wheel, I always start in 1st gear.