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I recently bought a 3.73:1 diff from an 83 4dr corolla, and a "semi-header" manifold from a 80 corolla wagon...
Question is, if I install these on my 77 te38 automatic, how would these improve or affect the overall performance?...

Right now I have the stock manifold with stock size exhaust and a 3.90:1 diff. It runs good but the rpm's are too high I think...
Haven't put a tach yet, just by the way it sounds while going at 60 or so...
I'm looking for lower rpm's on the highway, and a bit more power out of the old 2tc...
thanks.

I really dont know what a "semi header" is, but if its a "stock" manifold I doubt it will make a noticeable difference. On the other hand your rpms will go down with the new diff. So I guess you will be happy!
But on the other other hand...... Looking for more power and lower rpms make no sense. The more power and the higher the gears the "faster" the car will go and use the power. Adding power and lowering the gears you are pretty much throwing money away. So Im not sure exactly what direction you are going with the car, but it looks like you need to decide on power or drive ability.
I will give you another tip. I have a 5 spd and sometimes when I drive I think Im in 4th gear and I am on 5th. So I guess they do feel like they are high. Your actual speed might change also.

Thanks bro...
I do mostly highway driving and the wagon won't go past 60 without the engine sounding as if it's going to thru the hood...
I'm not looking for a race car i just want it to cruise easier...
As for the "semi header" that's a stock manifold out of a 80-81 corolla... it has dual outlets, and the down pipe forms a "Y"...
i also plan on going with a larger diameter exhaust...

My brother has a lift back with the factory 4-2-1 manifold+down pipe you are talking about. That manifold, coupled with a 2" exhaust really woke up the stock engine in that car!! That manifold is as good as you can get without buying a header.
I used to own a 79 automatic TE51, it had the 3.90:1 gears and turned something like 3600rpms at 60mph. You need steeper gears, taller tires, or an overdrive transmission to drop those rpms a bit.

Ok... thanks
It had a 4.10:1 from the factory, changed it to 3.90:1 a couple of years ago but still the rpms are high... By "steeper" what do you mean? 4.11 or 3.73? I'm running 195-50-15s...

Im sorry to say this, but if you are running 15s with 3.73 and you still think the rpms are high............... The problem is you!!!
Without a tach its kind of driving blind. You really cant go by sound. Do you have a cam in it or do you know? That can be the next problem.
Do you have the 4.10?................

Madslammer wrote:Ok... thanks
It had a 4.10:1 from the factory, changed it to 3.90:1 a couple of years ago but still the rpms are high... By "steeper" what do you mean? 4.11 or 3.73? I'm running 195-50-15s...

I mean 3.73, or even 3.58 gears to drop your final drive ratio. The 195/50R15's are only slightly shorter then factory 185/70R13's.

baldo wrote:Im sorry to say this, but if you are running 15s with 3.73 and you still think the rpms are high............... The problem is you!!!
Without a tach its kind of driving blind. You really cant go by sound. Do you have a cam in it or do you know? That can be the next problem.
Do you have the 4.10?................

The 4.10 was busted... I don't remember if I threw it away or have it in my old house. I now have the 3.90 on... I bought a 3.73, just wanted to make sure it would work... No cam, just all factory OEM never been touched...

bubbajohnson wrote:

Madslammer wrote:Ok... thanks
It had a 4.10:1 from the factory, changed it to 3.90:1 a couple of years ago but still the rpms are high... By "steeper" what do you mean? 4.11 or 3.73? I'm running 195-50-15s...

I mean 3.73, or even 3.58 gears to drop your final drive ratio. The 195/50R15's are only slightly shorter then factory 185/70R13's.

3.73 it is then... thanks ...

Well, finally got the 3.73:1 installed... runs much better, a little bit slower when accelerating but it runs great on the freeway, i have a tach now, it reads 3,300rpm at 60mph. Don't have the data before the change but it sounds lower to me. I'll be putting the manifold next plus some mods on the exhaust pipes... Just have to find a new muffler shop, the guy i always took my cars to, passed away last week... so that's all for now... thanks