Bigger Tires/Gear Ratio question

[Trinidadwho]

Hello everyone,

I just rebuilt my 302 5.0 on my 1990,, also rebuilt the transmission AOD, went camping (Drove about about 100 to get there) and whenever I hit a long slope, it would slow down from like 70 to about 45-50. Short slopes not a big deal but, I went back to the tranny shop and he didnt even drive it, but did suggest that its the 33" tires and we need to change the gears on the differential ($1200). My question is...are other 90 FB having the same problem, do these tires make that big of difference? 45mph up a slope not a steep one and the longer it is the more the engine struggles to keep the speed. He (Tranny guy) said that the power comes from the engine and should have it checked out. I think the engine may have a leak from the exhaust manifold to the headers but, I dont think that causes loss of power right? (Im taking it back to get that checked out at the place I had it rebuild), thanks guys!

 

[Bully Bob]

Yep..,

That 302 is pull'n a lot of weight.

1st. thing to know is what gears are in the pumpkins now...?

A guess would be 3:50's. Those & 33's are not a good combo for hwy. hills.

Does the trannie downshift...?

 

[Trinidadwho]

Yes, and the engine sounds like its going 75mph, I may gain another 5mph, but I just keep it slow so I don't strain the motor which has less than 600 mi on it.

 

[wileec]

He is right the 33s on stock gears will do exactly what you describe. Re-gearing to 410 will get it close to stock performance. I over-geared mine with 456 and roar up hills easily but pay the price in lower MPG.

The 302 is not the best power for the auto tranny.

 

[Trinidadwho]

...overgearing sounds like something I may want to do, but how much of a gas difference does it make? It's not my daily driver. Also, I wouldn't be able to go back to stock tires right, will I always need to have 33" tires or can it vary? Do I need to know what gears are in now or do I just ask for the ratio Im interested in? Thanks again guys!

 

[Bully Bob]

"I wouldn't be able to go back to stock tires right"

No.., not really... short shift ratios & hi RPM's

However, you could go back to stock tires now...& prob. have enough power to maintain hwy. speeds.

"Do I need to know what gears are in now or do I just ask for the ratio Im interested in?"

I would want to know B/4 starting...? There's usually tags in the door jams or, on the pumpkin bolts that state the axle ratio.

FWIW.., I run 456's with 32's & couldn't be happier. Good milage as well.