I have a 1988 toyota 4 runner 4wd with 10.50x31r15 tires. It was real sluggish, especially uphill, until I changed the spark plugs (I found one with no gap at all). I want to change the rear gear to fit the new tire but I'm not sure what size to get. Any suggestions/

 

Welcome to Yotatech. Is it an auto tranny or manual, it makes a difference.

 

Thanks, it is an auto tranny

 

If you have stock 4.10's I'd go to 4.56's.

 

i thought a lot of the autos had 4.65's stock? what is the stock gearing, and stock tire size?

 

Both axles?

 

Yes you must do both axles. If the truck came stock with 28" tires theres a good chance it had 4.10's - 4.56's or 4.88's will make the difference you require if that is the jump in tire size you went with (28's to 31's). You have to check yoru axle code on your door jamp sticker. It'll say something like A/TM x294 or x254 or something like that.

 

according to the sticker it has 4.10's. which is better 4.56 or 4.88?

 

Go with 4.88. My 3.0 auto came from the factory with 31" tires and 4.88 gearing.

 

the stock tire size for mine is 225/75r15 with 4.10 gear

 

The configuration on most 1st gen 4Runners was 4.10 for manuals and 4.30 for automatics. I don't believe any of the 1st gens came with 4.56 or 4.88, those were the 2nd gens...correct me if im wrong.

 

Yeah but they didn't come with 31" tires either. IIRC the 4th gear (OD) is .705 (or .688) with the auto trannies between the years and that plus the tire size will be the key for axle gearing.

 

Yeah, that sounds right. I just remembered that the autos had a higher (numerically) gearing that 4.10. if you have 4.10's stock 4.88's are about the right size for 32's, but dont let that stop you from using them with 31's

 

What you guys need to keep in mind is that 4th gear in the auto is HIGHER than 5th gear in the manual. So the axle gearing in the auto needs to be a full step lower to make up for it.

4.88 gearing with 31 inch tires was still a little doggy for my auto tranny. It would have been about right with 30 inch tires IMHO.

For you guys driving 5 speeds and wanting to share gearing experence with us auto guys, please image that you have another gear (6th gear) and ask yourself how would you gear for that? Then share that with us.

 

the thing to do is look for a gear/tire size calculator, and you can find out what size would put you closest to stock.

 

Yeah the problem with that is most of them I've seen are for the 5 speeds. Some I've looked at were way off. Some of the general ones for any car or truck assume a final drive gearing of 1:1 and the Toyota auto OD gear (4th gear) is .705:1. 3rd gear is 1:1, to use a calulator that assumes 1:1 you would be gearing your truck to run in 3rd gear LOL.

With the auto tranny, Toyota geared these wimpy engines to go 120mph and some can't even pull 70mph up a slight incline, yeah if you have 300 hp you would want higher gearing, go with something higher, but with a wimpy 120-150 hp you need to gear lower than the standard gear/tire calulator.

 

most of them you enter the gear ratio, axle ratio, old tire size, and new tire size, and it tells you what axle gearing you want to get back to stock. The top gear on a w56 (common yota P/U manual trans) is less than 1:1, and 1:1 is forth gear for a w56 (i cant remember the exact ratio off the top of my head).

Most newer cars/trucks are designed to have the top gear less than 1:1 for better gas mileage.

 

Oh really, I haven't seen one like that. From this source the W56 has a 5th gear of .850 : http://toyota.off-road.com/toyota/ar....jsp?id=186415

 

ok so what should i do 4.56 (that's what the calculator says) or 4.88? how much does this cost to have done?

 

1)I've always read that the auto trans requires[and in the applicable years, was sold with] 4.88 axle gearing for "normal" drivability w/ 31" tires. Keep researching it to be sure.
2)Just had it done on my '91 22Re 5-sp P/U.(4.11 to 4.56;29" to 31" tires) About $1400 out the door using "good" parts[Motiv gears, Timken bearings, etc] w/ 6 mo. warranty from a shop that's done it before many times, here in 'expensive' SoCal/L.A. area.