Just order 4.88 gears. Did I choose the right gear?

Sounds like you need the next lower gear to me, you're at the sweet spot for the overdrive to kick in.

Reading here, most report that the next lower gear is needed for the automatic transmission vs the manual.

 

I was told where I ordered the gears to go with 4:56 gears but I went with the next up 4:88, factory was 3:91, so you think I need 5:29 gears?

 

Just called a friend of mine he said from what I'm describing he belives instead of my truck shifting from overdrive to passing gear that it's just going in and out of lock up and may have something to do with speedometer being off? What yaw think and what would be a fix to this?

 

I don't think you went low enough:

Here is my reasoning:

30.5" tall tire at 60mph with a 3.91 gear ratio equates to an engine rpm of approximately 1800

35" tall tire at 60mph with a 4.88 gear ratio equates to an engine rpm of approximately 1950

35" tall tire at 60mph with a 5.29 gear ratio equates to an engine rpm of approximately 2130

I believe the problem lies in this little fact here:

30.5" tall tire weighs about 37lbs on average with a wheel weight of 23lbs average for a factory 16x7 wheel for an average of 60lbs of unsprung weight per corner.

35" tall tire weighs about 63lbs on average with an average wheel weight of 30lbs(based on alloy) for a 12x 15" wheel for an average of 93lbs of unsprung weight per corner.

Honestly I think the extra weight per corner combined with the diameter is killing you. I would have chosen a 5.29 gear set, it would have only added about 200rpm at 60mph and gotten you into a better part of the torque curve, mileage is going to suck no matter what you do at this point, so I wouldn't have tried to get back to the same rpm area as a factory set-up, especially with an 18yr old engine.

This is all based on a .70 overdrive ratio calculator.

Another consideration is vacuum, I don't know how Toyota programs their ecm to trigger shift points, but I would think vacuum, TPS position and rpm would figure into it.

At this point, I would try to find someone who has been down this road and already did the legwork. Have you been thru the build threads to try and find someone with a 1st gen automatic and 35's to see what gear they went with.

I know several have mentioned 35's, but most were running a manual transmission.