g741.org

the other day. I have no history on my M37B1 and this summer while doing a brake job realized the rear had a locker. My Son is out of work and he had the time so we jacked up the rear end and checked out the ratio. As I had hoped after finding the locker, the ratio is 4.89.

I'm sure that if your rear is so equipped, your front punkin' is the same?

Highway speeds!!

i can do that with the 5.83 with a 318 and new tranny lol
nice find i would have loved to find that

Wow, you must be tickled. Thats a heck of a find.
4.89's are going to be one of my first major upgrades. As soon as I can afford them.

Really my second clue was on that first work run with the pallets of clay targets. I went by one of those speed readouts that the PD puts out and the speedo was reading low compared to the radar readout. But until I did a wheel to drive shaft count I couldn't be sure. Whom ever did the original restoration must have done it along with the lock out hubs. It does beg the question though that when the restoration done, guessing 15 years ago, why was so much Bondo used when sheet metal was a lot cheaper and more available?

Wayne64 wrote:...why was so much Bondo used when sheet metal was a lot cheaper and more available?

I'm guessing that whomever did the "restoration" was a decent mechanic, but had no body experience and was afraid to try. Bondo was the quick 'n easy solution...one which I am guilty of having used years ago when "go" was more important than "show."

I'll stick with my 5:83's.

Why is that Chunk?
Other then cost they look like a super mod.
Seems a higher road speed with lower drive-line rpm would be desirable. Less wear on parts with better drivability on today's roads.
Not trying to dis you, just curious why you feel that way.

I agree with Chunk. If I decide I want a higher road speed at lower RPM then I'd consider other ways like overdrives or trannies with a higher top gear to get it. I prefer to keep the low end gearing for the low speed off road driving.

I would have to agree with Chunk - at least if the stock engine is being retained. The flat 6 is a dog with the 5.83's, I would almost think that 4 gear would be almost useless with the 4.89s unless your in low range or running downhill in high range.

The sheer cost of the swap isn't worthwhile either IMO. Its cheaper and easier to just drive 5mph slower. An overdrive trans would be a far better upgrade. Taller tires would slow the driveline down as well for a given speed, and they would be cheaper too.

The only upside I can see is that the gear set itself would be stronger due to the extra gear teeth thrown in to the mixture.

But I wouldn't change out the 4.89s if somebody had already put them in...

Great input guy's
The thing is, in my case I need to rebuild my front and rear members. My ring and pinion's, spider's, and bearing's in both are shot. (I can turn my rear half way around before it catches) Price of parts to do those in 5.83 is almost the cost of the 4.89's with pumpkin's already done up.
I am also keeping my truck stock. So no larger tires, or different running gear components are going to be used. Unless they can be hidden like a set of 4.89's.
As far as being doggy...I never use first in my truck. I was thinking the 4.89's might bring that gear into play more often.
My truck also seems to have ample power. Not sure if it's due to the Chrysler industrial replacement engine...
How's your truck go Wayne64? Any issues hauling that big load of clay birds?

Captnsim wrote:Great input guy's
The thing is, in my case I need to rebuild my front and rear members. My ring and pinion's, spider's, and bearing's in both are shot. (I can turn my rear half way around before it catches) Price of parts to do those in 5.83 is almost the cost of the 4.89's with pumpkin's already done up.
I am also keeping my truck stock. So no larger tires, or different running gear components are going to be used. Unless they can be hidden like a set of 4.89's.
As far as being doggy...I never use first in my truck. I was thinking the 4.89's might bring that gear into play more often.
My truck also seems to have ample power. Not sure if it's due to the Chrysler industrial replacement engine...
How's your truck go Wayne64? Any issues hauling that big load of clay birds?

Since the last time I drove an M37 was in 67 with any kind of load I can not make the comparison. I will say I can start out in 2nd with the 4.89s but when I hauled the load I used 1st to get her rolling. I felt no problems at all with the 2200 pound pallet loaded and no one was honking their horn about me going slow, as I wasn't. I guess it's a matter of where you live and how you use the truck. Me I'm happy with my discovery.

The real load vs power vs gearing issue is in 4th gear on a level road. or uphill. The 489's may force you to downshift into 3rd faster than the 5.38's.

How does the 489 gears set conversion compare price wise to an overdrive?

I have built two vehicles in the last few years. The first was a full sized 64 Ford custom 500 with a BBF and C6. 4.11 rear with a Gear vendors overdrive. The latest build was a 79 Ranchero that I built a beefed up AOD for with a 3.50 rear. I pulled a boat with both and at times had to either switch off the GV unit (64 Ford) or the Ranchero would down shift it's self. So if the M37 had a .76 over drive and I was climbing a hill with a load I would still have to drop it down a gear. I consider the 4.89s as a bonus for my use, if I didn't have them the GV unit would be a second choice as you get not only overdrive in 4th but actually get a possible 8 forward ratios and two in reverse. JMHO

The GV is a great unit - If the wheel base is there to install it. It would be a challenge to get one in an M37.
Downshifting is a fact of life, there is no way around it. If a load can be hauled without downshifting, then I'm sure I can find a heavier load to haul...