Gearing for performance TH700R4 + 3.73 ?

[Logbed]

Hi,
I have an '85 longbed 2wd that has a well built 305 with the basic upgrades (Edelbrock 500 carb, performer intake, performer plus cam, HEI and 1.5in long headers). Being adjusted in a hub dyno it pulled 190hp/4600 and 250ftlbs/3100 (at the hubs). The engine also has low mileage and budget-wise I'm not into a 350 or 383 build right now. The truck is pulling nicely once it gets to the powerband at 3000rpm, but the "launch" from the traffic lights, right from the 2000 stall speed is not so cheerful. What I was thinking was swapping the TH350 to a mildly prepped "stage1-rebuilt" TH700R4 with a higher stall torque converter and possibly also swapping the gear ratio from 3.4 to 3.7 as the differential will need shimming anyhow. The idea is mostly to have more crisp acceleration (with some wheelspin ) by the help the low first gear. Overdrive would be nice too, specially if I go with the lower diff gearing. Going from 3.4 to 3.7 I'd still have around 15% longer gearing overall with the 4th gear (not so important anyhow, I drive mostly in town and practically never faster than 55mph). (Edit: The tire size is 275/60R15. Tire height 28".)

Thoughts, experiences?

 

[nvrenuf]

Tire size?

 

[Logbed]

Tire size?

Good point, 275/60R15. 28" tire height!

 

[82sbshortbed]

I've got almost that same set up on mine but, I have a 454 with 700r4, 2200 tc, Trutrac 8.5 10 bolt 3.73 posi rear end, 275/60/R15 tires.

Had a th350 behind the bbc but it was running 2800 at 55 so I switched to the 700r4 for od. Haven't gotten it back yet from the shop but should be this week. I think it'll be a nice setup when I get it back.

 

[SquareRoot]

Had the same setup in an 85 el Camino. World Product 305 heads, 700 and 3:73 gears. Despite my comments about 305's, it ran pretty darn good. The 3:73 we're a perfect compliment to the 700.

 

[bucket]

I agree, 3.73 should work pretty darn well.

 

[Logbed]

Had the same setup in an 85 el Camino. World Product 305 heads, 700 and 3:73 gears. Despite my comments about 305's, it ran pretty darn good. The 3:73 we're a perfect compliment to the 700.

Which model World Product heads did you have? How big and around where in the powerband was the power improvement compared to stock heads? Asking out of interest, maybe something to do during the next winter?

Right now my assumption is that I'd get more "0-60 performance" with drivetrain upgrades (3000 stall turbine, low first&second gears of the TH700R4 and 3:73 gearing) than what a heads upgrade could bring to me with the current drivetrain, am I right?

 

[SquareRoot]

Which model World Product heads did you have? How big and around where in the powerband was the power improvement compared to stock heads? Asking out of interest, maybe something to do during the next winter?

Right now my assumption is that I'd get more "0-60 performance" with drivetrain upgrades (3000 stall turbine, low first&second gears of the TH700R4 and 3:73 gearing) than what a heads upgrade could bring to me with the current drivetrain, am I right?

They were the Torquer SR 305 heads. My experience was 12-13 years ago. I see they still make them but at the current cost of $781.29 per head, NO way would I put that kind of money into a 305. Times have changed. In your case, I would do the trans swap (700) and gears (3:73) and call it good. It will completely change the nature of your truck.

 

[bucket]

They were the Torquer SR 305 heads. My experience was 12-13 years ago. I see they still make them but at the current cost of $781.29 per head, NO way would I put that kind of money into a 305. Times have changed. In your case, I would do the trans swap (700) and gears (3:73) and call it good. It will completely change the nature of your truck.

Holy crap those are expensive now!

 

[Itali83]

You’re in the right track with your thinking about doing gearing and trans mods over a built 350/383 etc. I’m playing devils advocate and saying go 4.10’s. The overdrive and your overall driving style/needs (not much Highway or high speeds) I think the 4.10’s will just really give you the kick in the pants you’re looking for and won’t be terrible to live with.

Ben

 

[Logbed]

You’re in the right track with your thinking about doing gearing and trans mods over a built 350/383 etc. I’m playing devils advocate and saying go 4.10’s. The overdrive and your overall driving style/needs (not much Highway or high speeds) I think the 4.10’s will just really give you the kick in the pants you’re looking for and won’t be terrible to live with.

Ben

Thanks, 4:10 made me think, I'd still have 10% longer 4th than my current 3rd, but the 1st would be 30% shorter!

 

[Logbed]

How is it, if the quicker ratio, higher stall and lower 1st gear make the wheels spin, is it always going to be one wheel only unless I have a limited slip diff? And If I install limited slip kit, am I too modestly powered to spin both the wheels? (You wouldn't think a middle aged man has problems like this )

 

[75gmck25]

I’m not sure if you would have the power to break both wheels loose, but I think it would probably work because the rear of the truck is very light.

Also remember that when you spin both wheels you have to deal with the rear end swinging around to the right because you are no longer dragging one tire. With this amount of power it will probably be a slow turn, but may still be enough to bang into a curb or car that is on your right.

 

[bucket]

How is it, if the quicker ratio, higher stall and lower 1st gear make the wheels spin, is it always going to be one wheel only unless I have a limited slip diff? And If I install limited slip kit, am I too modestly powered to spin both the wheels? (You wouldn't think a middle aged man has problems like this )

If you shock the driveline with enough horse torques, both tires will spin

With a one tire fryer, going straight or turning right will almost always spin just one tire. The trick is to kick it to the left and be prepared to steer into it.

 

[Logbed]

I’m not sure if you would have the power to break both wheels loose, but I think it would probably work because the rear of the truck is very light.

Also remember that when you spin both wheels you have to deal with the rear end swinging around to the right because you are no longer dragging one tire. With this amount of power it will probably be a slow turn, but may still be enough to bang into a curb or car that is on your right.

Not worried about the rear swinging, more like waiting for it, although like you said, I must be realistic with the power I have...
Off topic: Actually, right now there's 6" of new snow outside and my daily driver, a TT Quattro 3.2 with studded snow tires, had the ESP turned off like I have it most of the time. So today was all about avoiding curbs while drifting all four tires broken loose and pointing somewhere else than where the car was going

You must be registered for see images attach