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post #1 of (permalink) Old 10-29-1999, 09:56 AM
gregcs
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Manual Transmission and Gearing

Hello Folks,

I know I might get blasted for asking this question about my Ford Truck, but I am having difficulties getting a clear answer. I have a Jeep as well just no current question on it.

I have a 93 Ford F150 XL 4x4 truck with the manual 4 speed which has the practically useless granny/1st gear. I am using "useless" very loosely. Obviously it has its uses, just I don't use it. Pretty much the only time I use it is if I am fully loaded AND on a hill starting off.. which is very very rare. Maybe once.
Here are my question:

If I go to the 31" tire from stock will the granny/1st gear become a useable 1st gear??

This is important... Right now with stock the granny/1st gear is too low to really use (other than serious towing) and the 2nd gear works ok for take off, but it is actually border line on take off... it can feel boggy at times. It's like I need a gear that is between the 1st and 2nd gear. I have a second F150 where the 2nd gear on it is perfect. SO... you see my problem is I don't want to put on a 31" and find that the granny/1st gear still isn't really suitable for normal take off and then because of the larger tire my 2nd gear becomes useless for take off... bogging down too much.

I am leaning towards definitely getting 31" tires... just don't know how much it will make 1st gear better for take off or how much worse it will make 2nd be.

HELP... Especially those who have done this.!! Everything is stock on this truck.

Again sorry for posting here, but I know there are many of you who have Ford Trucks as another recreational vehicle and work vehicle.




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post #2 of (permalink) Old 10-29-1999, 04:29 PM
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Re: Manual Transmission and Gearing

Greg, this could just as easily be a Jeep question. You need to decide which is more important to you: 31" tires, or decent power at highway speeds. Going to larger tires will, indeed, make first gear appear to be more "usable." However, you will sacrafice highway power in the process. You will no longer be able to take advantage of the truck's full power curve.

If you want 31" tires, your best option is to drop the rear end gearing one size (3.55 to 3.73, 3.90 to 4.11, etc.) and get better second gear performance.

Hewgag

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post #3 of (permalink) Old 10-29-1999, 04:41 PM
gregcs
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Re: Manual Transmission and Gearing

Thanks for the reply...

The thing is... right now by the time I get to 4th gear and doing 55 to 60 I feel I could use a 5th gear. So it sounds like this may help me out on that end. I just don't know how much 1st gear will improve to being like normal. I am scared 1st will barely improve and then second will be not usable for take off. The only way to really know is to do it... and know one will do it without buying. No testing can be done.

Thanks again

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post #4 of (permalink) Old 10-29-1999, 04:50 PM
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Re: Manual Transmission and Gearing

The cheap way is to pick up a pair of used 31s from a junk yard for $25 each. Put them on back and check 'em out.

Hewgag

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post #5 of (permalink) Old 10-29-1999, 05:48 PM
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Re: Manual Transmission and Gearing

first is a granny low gear and will still be useless on takeoff, I have a gmc tow vehicle, my tires measure 30 inches tall with 4.11 gears and my first gear (6.55-1) is totally useless for normal driving. wounderfull for towing my jeep though.
you should have a t-18 tranny I think? they did make a not granny first version of that tranny for jeeps and scouts that you may be able to pull the guts out of for yours, then go to a tall rearend gear to get highway cruisability and good get go off the line.

post #6 of (permalink) Old 10-29-1999, 10:51 PM
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Re: Manual Transmission and Gearing

I had a Chevy with Granny 1st gear. It came with 30" tires and 1st gear was pretty "useless" with them. I switched to 33" tires and 1st gear became useable and 2nd gear was to high to start off in. My chevy had a 6.32:1 first gear and 3.73 rear end, assuming your gears are similar you canexpect similar results depending on what size tires you are starting with.

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post #7 of (permalink) Old 10-30-1999, 01:58 AM
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Re: Manual Transmission and Gearing

You have something that is great for what it was designed for, but the problem is your are trying to use it differently than it's design purpose. Granny gear, which BTW, lots of people would consider swapping their first born for, (just kidding) is not supposed to be used for regular driving. In a hwy application it is designed to start a very heavy load moving so that your regular street gears can take over and pull the load. In off roading is is used for a different purpose, but just as important - going SLOW. If you really want to get the best use out of your tranny, set it up for 2 through high for the concrete, and leave 1st or granny for what it was designed for. Do not figure it into your "take off from a stop light" type driving. Don't know what type of tranny you have, but there are basically 3 different styles:
1) 1st through high for all driving. High being direct 1:1
2) 2nd through high for all driving. 1st being a granny for starting heavy loads.
3) 2nd through direct (1:1 ratio) plus overdrive. 1st being a granny gear and the highest gear being an overdrive, less than 1:1. This is the most versatile transmission. A very low, seldom used gear for starting heavy loads and a final high gear that is only used on the highway at speeds of 35/45 and up.
Sounds like you have a #2 type transmission (my own numbers). This transmission was designed for delivery type use where heavier loads are frequent and short NON highway trips are the norm. A farm truck, delivery truck, lower speed heavier hauling type truck. You can change the tire size and/or change the axle gears and move this truck into a different catagory, but it really will not fit there comfortably. Granny gear is often non syncrornized. It usually has heavy springs to keep you from shifting into it accidently. Yes, it can be set up so that it is a usable drive gear, but look at the ratio differences between the gears. The first drive gear is usually in the 3.xx range, 2nd in the 2.xx range, 3rd in the 2.xx to high 1.xx range, but the granny is usually a 5.xx or 6.xx gear. Look at the gap between it and the next gear. It isn't designed for regular use.
Hope this helps.

Doug '97 TJ
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post #8 of (permalink) Old 10-30-1999, 09:45 AM
 
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Re: Manual Transmission and Gearing

I do not remember what motor is in front of the transmission but it proberly the 300 6 or v8 both are good motore for adding tire size. The transmission is every wheeler dream. I wish I could find one for my jeep. You could run 33 or 35 with minor differents in speed . if it too noticeable up the axle gears but keep the trans. The granny is the ulitmate. Nearly all trans except for the overdrives are going to have a 1:1 final. So just consider the t18 as a three speed and forget about granny till you need it.

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post #9 of (permalink) Old 10-30-1999, 10:30 AM
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Re: Manual Transmission and Gearing

Doug, Thank you for the informative reply. I kinda felt like I was trying to force it out of what its purpose was for. Ok let's start over then.

I have P235's on the wheels now. Going to 31x10.50's... will that make my 2nd unusable. I was told by the tire dealership that once everthing was mounted I would be looking at about 1" to 1 1/2" difference. I don't know if that is correct, but I guess this is my last question.
You know if it looks like I need to leave everything as it is then I probably need to sell it and get me a truck more suitable to my needs. Any takers <smile> I kind of want option #3 the fully universal tranny.

Again thanks and I look forward to your reply.

post #10 of (permalink) Old 10-30-1999, 12:39 PM
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Re: Manual Transmission and Gearing

I can't give you specifics as far as tire size, compared to axle ratio, compared to granny etc, but am sure others can. Bottom line is, if you want to keep that tranny, configure it with tires and axle ratio so that 2nd gear is comfortable to start off in normal driving. If you want to lean toward better hwy performance, adjust gears and tire size so that starting off in 2nd is just beginning to be a little difficult. You always have granny if you need it. This will give you a little better hwy performance. If you carry that idea to the extreme so that you HAVE to use granny to start all the time, your hwy performance will benefit, but your overall performance will be not be good at all, and you will have lost all the great benefits of that granny gear. I'm going to guess that about a 3.73 or 3.55 - something in that area with 31" tires will give you reasonable performance. The 3.73 for more power, less hwy speed. I think that if you get higher than a 3.55, something in the low 3.xx or high 2.xx, you will get into the area where granny will have to be used to start off. Others can probably give you better info in this area.

Doug '97 TJ
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