Help from the herd on upgrade options

[kristopherdb]

So my 85 4x4 flareside with the l6 and manual 4 with granny gear is very much still a work horse and wants to climb mountains and pull things. However my goal is a cruiser that can keep up with today's traffic on our freeways here in Portland, OR.

I have to work on the transfer case because it keeps falling into 4H so before I go tearing out transfer cases and spending a few hundred more on a rebuild kit for it is there a path or article I should follow to get me from farm to fantastic?

I would guess the tranny needs replaced with an overdrive one? Not sure how I figure out what would fit or not, I am in Portland so on CL or the marketplace I see the picking is good and I can get a whole setup or pick pieces but have no idea even were to start. I wouldn't mind an automatic. Right now when I hit a rock on the road it feels like I am jumping the grand canyon. Granted I drive a 7,000 recent tundra and only have it to compare too. It sounds like its doing 200 MPH when its doing 55 etc...

I just need some direction and you guys have always been very helpful pointing me in the right direction.

[Gary Lewis]

One popular upgrade on these trucks is to go to a tranny with an OD, as you mentioned. That drops the RPM and the noise, and makes a world of difference. But, these trucks were made when overdrive transmissions were just coming in, so the pickings from this era of trucks is slim, and not too good. In fact, none of the OD transmissions from this era none were really strong enough to tow very much in stock form.

But not long afterwards Ford came out with the ZF5 manual and it is stout, a serious truck transmission. I discuss the one that was intended for Dad's truck here: http://www.garysgaragemahal.com/transmission.html. But, since you have the small-block bolt pattern on the 300 six you won't have any problems mating a ZF5 to your engine. And the transfer case will bolt right to the back of it - but you have to find a 4wd version.

If you want to go with an auto you have two choices - the AOD or the E4OD. The AOD was originally not very strong, but can be built with aftermarket parts into something that has plenty of strength. And the E4OD had some early problems but later versions from the factory were quite strong. However, it takes an outboard computer/controller and you are looking at $800 in addition to the price of the tranny.

I'd recommend the ZF5. First gear is a granny gear and you can move mountains w/o going into 4lo. And the 5th gear is a good OD ratio that will drop your noise and RPM down dramatically. But, what rear gears do you have now?

[kristopherdb]

One popular upgrade on these trucks is to go to a tranny with an OD, as you mentioned. That drops the RPM and the noise, and makes a world of difference. But, these trucks were made when overdrive transmissions were just coming in, so the pickings from this era of trucks is slim, and not too good. In fact, none of the OD transmissions from this era none were really strong enough to tow very much in stock form.

But not long afterwards Ford came out with the ZF5 manual and it is stout, a serious truck transmission. I discuss the one that was intended for Dad's truck here: http://www.garysgaragemahal.com/transmission.html. But, since you have the small-block bolt pattern on the 300 six you won't have any problems mating a ZF5 to your engine. And the transfer case will bolt right to the back of it - but you have to find a 4wd version.

If you want to go with an auto you have two choices - the AOD or the E4OD. The AOD was originally not very strong, but can be built with aftermarket parts into something that has plenty of strength. And the E4OD had some early problems but later versions from the factory were quite strong. However, it takes an outboard computer/controller and you are looking at $800 in addition to the price of the tranny.

I'd recommend the ZF5. First gear is a granny gear and you can move mountains w/o going into 4lo. And the 5th gear is a good OD ratio that will drop your noise and RPM down dramatically. But, what rear gears do you have now?

How do I know which gears I have in the rear?

[Gary Lewis]

How do I know which gears I have in the rear?

If you have the certification label on the driver's door post you can decode it on the page in the menu of Specifications/Certification Label. At the bottom right of the one on that page you'll see "38", and if you click on that it'll take you to the page in the menu of Specifications/Axle Ratios where you can decode the axle number from your certification label and/or decode the tag that may be on the axles.

The reason you want to know that is the OD ratio of the ZF is .76:1. And the AOD's OD ratio is .67:1. So, if you have the ubiquitous 3.50 or 3.55 axles then the ZF5 would give you the equivalent of 2.66:1. That worked well on Dad's truck with a warmed-up 351M, dropping the RPM at 65 MPH to about 1800, and it pulled any hill we saw at 65 MPH on the highway on cruise. And that should work well on a 300 six as that's close to its peak torque.

But, if you have 3.0 axles, which are uncommon - especially in 4wd trucks - your effective ratio would be 2.28 with the ZF and 2.01 with an AOD. That's too high and very few engines would like that.

[kristopherdb]

If you have the certification label on the driver's door post you can decode it on the page in the menu of Specifications/Certification Label. At the bottom right of the one on that page you'll see "38", and if you click on that it'll take you to the page in the menu of Specifications/Axle Ratios where you can decode the axle number from your certification label and/or decode the tag that may be on the axles.

The reason you want to know that is the OD ratio of the ZF is .76:1. And the AOD's OD ratio is .67:1. So, if you have the ubiquitous 3.50 or 3.55 axles then the ZF5 would give you the equivalent of 2.66:1. That worked well on Dad's truck with a warmed-up 351M, dropping the RPM at 65 MPH to about 1800, and it pulled any hill we saw at 65 MPH on the highway on cruise. And that should work well on a 300 six as that's close to its peak torque.

But, if you have 3.0 axles, which are uncommon - especially in 4wd trucks - your effective ratio would be 2.28 with the ZF and 2.01 with an AOD. That's too high and very few engines would like that.

As far as I can tell my code is 18

[Gary Lewis]

As far as I can tell my code is 18

I don't see a signature that tells me anything about your truck, but an 18 had either 3.00 or 3.08 gears. I would put both rear wheels on jack stands so neither touches and turn the driveshaft 10.0 turns, counting the rear wheel rotations. That will tell you for sure, but the ratio has probably not been changed.

But, assuming the 3.0 is correct, with the ZF's .76 OD you'd only be turning about 1600 RPM at 65 MPH. Let's see what David/1986F150six says his RPM is at 65 MPH. Perhaps the six will pull that.

[kristopherdb]

I don't see a signature that tells me anything about your truck, but an 18 had either 3.00 or 3.08 gears. I would put both rear wheels on jack stands so neither touches and turn the driveshaft 10.0 turns, counting the rear wheel rotations. That will tell you for sure, but the ratio has probably not been changed.

But, assuming the 3.0 is correct, with the ZF's .76 OD you'd only be turning about 1600 RPM at 65 MPH. Let's see what David/1986F150six says his RPM is at 65 MPH. Perhaps the six will pull that.

Thanks its kind of hard to read as its very faded. trans says "A" and Axle says "18" or "1B"

[1986F150Six]

Thanks its kind of hard to read as its very faded. trans says "A" and Axle says "18" or "1B"

Thanks for the invitation to the party, Gary!

But, if you have 3.0 axles, which are uncommon - especially in 4wd trucks - your effective ratio would be 2.28 with the ZF and 2.01 with an AOD. That's too high and very few engines would like that.

I am not sure I totally agree with that as my son's 1984 with 4.9L, 4 speed manual O.D. and 2.47 rear gears did fine on the interstate, until a hill came into sight! The 2.47 gears with .71 [?] O.D. = 1.75. With this arrangement, it could return 26 mpg @ 65 mph. This was before gasohol.

Regarding towing, it would not! It ran almost 40 mph in 1st gear and regarding acceleration, it was a dog. It idled @ ~8 mph.

With my 1986 F150 with 4.9L, 4 speed manual O.D. and 3.08 rear gears, @ 65 mph, the engine is turning ~1800 RPMs.

I believe the "ideal" axle ratio for a stock 300/4.9L and my driving style would be the 3.25 option.

[Gary Lewis]

Thanks for the invitation to the party, Gary!

But, if you have 3.0 axles, which are uncommon - especially in 4wd trucks - your effective ratio would be 2.28 with the ZF and 2.01 with an AOD. That's too high and very few engines would like that.

I am not sure I totally agree with that as my son's 1984 with 4.9L, 4 speed manual O.D. and 2.47 rear gears did fine on the interstate, until a hill came into sight! The 2.47 gears with .71 [?] O.D. = 1.75. With this arrangement, it could return 26 mpg @ 65 mph. This was before gasohol.

Regarding towing, it would not! It ran almost 40 mph in 1st gear and regarding acceleration, it was a dog. It idled @ ~8 mph.

With my 1986 F150 with 4.9L, 4 speed manual O.D. and 3.08 rear gears, @ 65 mph, the engine is turning ~1800 RPMs.

I believe the "ideal" axle ratio for a stock 300/4.9L and my driving style would be the 3.25 option.

David - Thanks! I knew that you'd have better info than I do.

Ok, you said the ideal rear axle ratio with your .71:1 OD would be 3.25, so you are saying the ideal effective ratio would be .71 x 3.25 = 2.31:1. So, the ZF5's .76 OD ratio x 3.08 axle ratio = 2.34:1 and that, too, would be essentially ideal - for your driving style?

[1986F150Six]

David - Thanks! I knew that you'd have better info than I do.

Ok, you said the ideal rear axle ratio with your .71:1 OD would be 3.25, so you are saying the ideal effective ratio would be .71 x 3.25 = 2.31:1. So, the ZF5's .76 OD ratio x 3.08 axle ratio = 2.34:1 and that, too, would be essentially ideal - for your driving style?

Yes, I agree.