Shift points on 200R4

[LukeZ]

hey guys, ( some of you may know me by now... I've been posting a lot lately because I can't decide what I want to do with my car) I have a question about my transmission.

It's a stock 200R4 on an 86 SS El Camini. Never been tinkered with or adjusted, as far as I have had the car (I'm the third owner) I have a 305, and 2.56:1 rear end gears, no posi. I was wondering if anyone could tell me the shift points (rpm or speed, which I know can vary from car to car) for this transmission, because I'm looking to upgrade to 3.42:1 gears, and I don't want to kill my mileage (at least 3 times every summer, I drive down to the beach on route 1 in Delaware at like 70 or 80mph and this is an hour and a half drive, and I only burn between 1/8 and 1/4 tank of gas). If I do get this swap, couldn't I ask the shop that's doing it to adjust the shift points on my transmission to make for a smoother ride? Thanks

 

[pontiacgp]

changing the rear end ratio will affect your gas millage but changing the shift points won't improve the mpg

 

[LukeZ]

changing the rear end ratio will affect your gas millage but changing the shift points won't improve the mpg

Any tips on a rear end gear swap? I'm not too sure where to start other than by calling my local transmission shop

 

[pontiacgp]

it depends on what's available in your area. If you could find a G body rear with a 3.42 posi that's the easiest swap.

 

[Bar50]

Just remember, for what its worth, Monte SS cars came with 3.73 gears for the most part, with a 215-65-15 tire which is roughlt 26 inches in diameter, taller tires offer a lower (numerically) ratio. Or a taller tire will turn less RPMs at the same speed then the shorter tire. See how your car does if you leave it in drive for a portion of the trip to answer your own question.

I haven't figured up my milage, but the car I just put together (a Monte SS) has the 200R4 and 3.73 gears with 26 inch tires and does fine. You will need to change or tune the governer in your transmission to match the ratio of rearend gear you are looking at.

Gear swaps from other 7.5's are doable, say from an S10 or Camaro/Firebird.

 

[LukeZ]

My car used to have 14x6 wheels, and now it has 15x7 rallies, with 205/70R15s on it. Mileage is fairly good. I was thinking 3.73s would be too high, so that's why I was just looking for 3.42s. I'm not an expert, but all I have to get is the actual gears themselves (performnce ring and pinion from Yukon or something) and a posi unit from like Easton or auburn, and some new fluid. Am I missing anything?

 

[LukeZ]

And this would be a 7.5in rear

 

[403Olds]

My wife's GP had a 305 200R4 and 2.56. I changed to 3.42, it's a whole lot more fun, wen from 21mgp to 19 mpg, but it was worth it. I never readjusted the governor, so in Drive at WOT, it shifts at 3K. I have to hold it in a gear to get to a 5K shift point.

 

[LukeZ]

I think I like the sound of a swap to 3.42, thanks for your input 403olds.

So if I keep the 7.5in, all I actually need is a new set of gears and a posi unit, right?

 

[403Olds]

Yes, gears and a posi. I got my gears out of a S10, they are the same.