I have a 98 expy with 5.4, Gibson headers, full flow master exhaust.
It has 33" tires and has no power since adding the tires a couple years ago.

I have lived with it since then I was only towing a small open trailer for my ATV's but now that I got my a Toy Hauler it has become and issue. Glamis and Pismo trips are not as much fun since the truck is having problems going over the smallest hills.

I want to know what the truck has now and what would you do. I want to go with 35" tires when the 33"s are done so I have to keep that in mind as well.

Here are some pics of the tags on the rear end and also the door jam. I need to know what I have to make my decision on what to get.

Door jam label


label on rear end.

 

if you plan on getting 35" tires and doing alot of towing i recomend 4.88 for the expy it will really help out towing the trailer, your highway MPG will suffer but towing will be much improved, you have a 9.75 rear axle genuin gear makes 4.88 for your axle and they have just the smallest of off throttle gear wine, but that is common with the lower(numericly higher) ring and pinions, good luck

 

Hey bigtruck

4.88.... dammm that is a low gear set.. I know it would be nice for towing but I think its a little too much for me.

so Rear is 9.75 and front is a 8.8 reverse right?

Since my tires are 33" and they are almost new I figure I will get 35"s when I replace those but thats a way from now... I just use my truck for towing and on the weekends with the kids..

So does my rear end have 3.73 right now?

 

I am also looking at doing gears in my truck. I have a set of 3:73's right now and i just put on an RCD 5 inch and 315x70x17 tires. I use the truck for jacking around in the sand and towing the bikes and boats.


any recomendations. I ma not looking for anything crazy

 

4.56's will get you back to almost stock gear ratio with the 315/70's hope that helps

 

That is what I was looking for, thanks. anything I should know before I put them in? or anything else i should add while I am doing them?

another thing what does this do to my gas mileage/rmps at speed etc.

 

If you are down on torque now and you are planning to put on 35's... do yourself a favor and get the 4.88's. You can thank me later, I went thru the same thing six years ago with my '73 F250

 

wow, 4:88's what type of r's will I be turning at speed with them? as it stand I am told that with a set of 4:56's I will be turning 3k at 65, that seems a bit high to me. As I only turn about 2k at the same speed.

 

no way will it be 3K maybe with overdrive off, with 35" and 4.56 you will be turning 2200 rpm at around 65-70, with 4.88 and 35" tires you will be at about 2500 rpm at 65-70 with overdrive on, good luck

 

I talked to 4wheel parts and that was what they told me, also its about $1000.00 for the setup installed.

i was wondering if anyone knows weather you have to do the front gears also, in the 4 wheel drive.

 

also is there a way to find out what gears will do the rpms?

 

I just did 4.56 gears and I also have 35" tires one. I am at roughly 2200 rpm at 70-75.

 

Hi Waterkc:

Yup - you must do front & rear in a 4x4 unless you intend to disconnect the front driveshaft and run as a 4x2

As for a gear chart, here ya go...

http://www.oly4x4.com/gearratios.htm

Check out a Ford dealer, and what they would charge for a Ford Motorsports gearset install. Just for comparison purposes. You'd get a good warranty, at least.

Cheers
Homo Habilis

 

if you plan on sticking with the 35's I would say 4.56. if you think you might go back to 33's someday I would say something less. I wish someone made a 4.30 gear set for the 9.75 rear and 8.8 front for my truck. I be getting that as I think that gear would be great for either the 33's or the 35's. I wouldn't get the 4.88's unless you want poor highway mpg's.

 

yeah I am working on getting a set of the 4:56's. They are freakin pricey! 500 a set and I need front and rear, then I still need to get them installed.

I took the advice of a the post and checked with Ford and they say that they do not install gears anymore due to some reason. lol.....

o well.

Can anyone recomend some good gears for me?