Disappointed in my gear ratio choice.

[Ziegelsteinfaust]

In my C10 I have a pretty close to 475hp 383 LT1 gen 1.5 or 2 depending on whom you ask backed by a TH700 with a 2500 rpm stall converter, and 30x9.5x15 tires.

I just had 4.88 gears, and a Detroit locker installed. To be honest I have been disappointed in my choice this weekend. Driving it around is fine. A little hard core, but not bad.

The problem is going for distance. I can start a burn out, but carrying it for distance my engine doesn't rpm hard enough.

I know my carb still needs tuning, but with the old 3.42's. It would carry the one tire fire for a easy 150 foot till my truck got out of shape. Now it is hard to get past 50 foot. Alot of that is due to the locker I know. As I have twice the traction to overcome.

Is this a normal issue where deeper gears do not burnout better due to greater need for rpm gain? Where my 383 could push the burn out with a decent amount of torque. It can not rpm hard enough to carry anymore.

I am trying to figure out where I went wrong or where I need to go right to bring my combo back togather. I have gone fairly extreme on the choices with a smogger spec motor as it is what I had. It is a damn fine motor, and I don't want to detract from it's builder. I am trying to come up with a concept of where I need to look. To bring everything back in line.

What makes a engine rpm hard throughout its rev range?
Let's stick with a 350 sbc as it is what I am most familiar with. The power band range I am looking at is 2000 to 6500 rpm. It helps keeps parts cost in check.

[b454rat]

Too much gear. Need alot of RPMs to spin the tires fast enough in all the gears farther down the road. Steeper gears isn't always the key. Not for burn outs, but my old car had 3.08s in it. Chipped a couple teeth, so swapped to 3.42s. I hated it. It didn't pull as hard, sucked on the highway, only thing that was marginally better was taking off in 1st on a incline. 461 big block 4-speed 79 Malibu....

[mongocanfly]

4.88 and a 30in tire...4.88 is really low for that dia tire..be good in the 1/8 or1/4
3.50-3.73 would be a better choice

[cadillac_al]

Those are some low gears. Can't you just shift it and burn through 3 gears? You'll probably be changing gears in the near future. It doesn't sound like a pleasant ride with the short gears. Those gears would be fun with a 283 or 305.

[burnin oil]

A little more tire hieght may help. We have 4.88s in the jeep with a 5spd on 32s and love them for its use crawling around the property and going into town. It's not to bad other than faster speeds. 60MPH is about 2500RPM. Perfect for a cruiser that does local runs. It would not be my first choice for the interstate though.

My K20 has 4.10s with a detroit and really doesn't spin the tires without trying. When I want them to churn I turn the wheel a little and stomp it. Once they are spinning you can correct it to go straight or exaggerate the correction and let the detroit keep pushing in the wrong direction. This may help. You may try a harder tire since they don't hook as well. As I got older I spend more time trying to make them hook. Tire smoke is impressive but it's slower and tires get expensive.

[Steeveedee]

It's well known to drag racers that lower gears help with traction control. It's easier to modulate the throttle to keep accelerating without spinning. That's the opposite of what you're after, though.

[Ziegelsteinfaust]

Originally Posted by Steeveedee

It's well known to drag racers that lower gears help with traction control. It's easier to modulate the throttle to keep accelerating without spinning. That's the opposite of what you're after, though.

Damn, that is what I figured.

[Ziegelsteinfaust]

Originally Posted by cadillac_al

Those are some low gears. Can't you just shift it and burn through 3 gears? You'll probably be changing gears in the near future. It doesn't sound like a pleasant ride with the short gears. Those gears would be fun with a 283 or 305.

It doesn't bother me as a sbc at 3000rpm is perfect to me, and I always have passing power.

I have parts for a hot 302 sbc with a forged crank, and virgin 327 block. It is looking like I may go this way now. Or a comparable 4.8 LS way

[Ziegelsteinfaust]

Forgot to mention.

I blame David Frieburger for this. 5.13's???

No wonder you let us all down, and went to 3.73's.

And I thought I was not extreme enough

[mattfranklin]

As I started reading, I thought I'd add a comment about how I'd seen a Freiburger (Roadkill or, more likely, Roadkill Garage) episode discussing that. And now it looks like we've probably seen the same discussion. :-)

[mattfranklin]

At what road speed do the tires stop spinning? That might just be the top end of the engine that you reach more quickly with the 4.88 gears. So either a higher rear gear or higher revving engine. It might be interesting to just keep a spare axle with the 4.88 and one with a 3.73. I'm assuming you still have the stock 12-bolt.

OR... Can you have a manual shift body installed in your tranny (or go in and adjust automatic shift points)? That might give you a chance to have some fun optimizing shift points for max burnout distance.

[Ziegelsteinfaust]

Originally Posted by mattfranklin

At what road speed do the tires stop spinning? That might just be the top end of the engine that you reach more quickly with the 4.88 gears. So either a higher rear gear or higher revving engine. It might be interesting to just keep a spare axle with the 4.88 and one with a 3.73. I'm assuming you still have the stock 12-bolt.

OR... Can you have a manual shift body installed in your tranny (or go in and adjust automatic shift points)? That might give you a chance to have some fun optimizing shift points for max burnout distance.

I do not know the road speed since I have not adjusted the speedometer gears to match the rear. But my guess is around 35 mph.

The 383 torques well with the 116 lsa on the cam, but I think it rev speed is not up to the gear ratio. It would be deadly with 3.73's, and I would of backed the combo with a th400.

I used the stock 12 bolt. My original plan was for a 14 bolt sf, but the 12 bolt is strong enough when built for my shenanigans. This is probably the point where a brand F 9" would pay dividends.

The trans needs a little tuning, but is really close. The trans guy is stupid busy, and I have been busy too. So dialing it in will take some time to get a spot.

The trans was built for the engine in a 2800 pound car before my most recent bout of insanity. So it is on the short list for replacement, and I will be getting a 4L80E soon to inflict my insanity henceforth onto. So I want to save the TH700 for the car again, and not destroy or modify it. So the 4L80 will be built to survive my needs.

I had decided on replacing the motor when I went with the 4.88's, but I thought with the 383 it would be a go to Jesus combo. Meaning my epic death was in short order, and all while unlocking GTA life points.

Right now I am leaning towards a 302 with AFR 185 heads, Victor Jr intake, and a Holley stealth terminator system to also run the 4L80. I have quite a few parts to start, and a good set of solid roller lifters. I have Dart 205cc aluminum eagles, but they are a touch big. The 302 will be more stable at 3000 rpm cruising in OD, and with the right cam. Combined with the gears I do have. Should be more then adequate for my needs. Plus be a touch easier on the pocket book with gas prices right now.

My outside choice is a 350 LT1 with a narrower LSA cam to rpm a bit harder then what a smog legal 383 would use.

The LS is still in the mix, but I can not piece meal it like I can a SBC. So it's all of the way or non of the way. Which changes options in my mind.

[kwmech]

Burnouts with a 700r4?? when the trans gives out post up the carnage

[burnin oil]

I love short stroke motors that wind out but I will tell you to forget it right now. Without spending stupid money the pistons are gonna be 11:1 high octane lovers. The heads will work great up top but will suck down low. The combo will need a cam that breaths to use those heads. Total picture is a fun motor that idles miserably and fouls plugs. Running WOT will be a blast but anything else will suffer along with the MPG. It's up to you but I wouldn't do it especially considering the low torque and the weight of our trucks.

No offense on this if it sounds wrong. I think you want a style and truck that roasts tires. Mess up the rear suspension and see what happens. Pull the shocks and drive it. If it spins then add a soft shock that you can tune enoughnto limit axle wrap. If nothing changes add stiffer shock and see if traction is lost. Drag racers spend countless hours reducing wheelnspin so an on doing the same ad you reduce the process. Have you tried raising the tire pressure? Let's be honest, rehearing again is cheaper than another motor.

[Ziegelsteinfaust]

Originally Posted by kwmech

Burnouts with a 700r4?? when the trans gives out post up the carnage

It's a level 2 with Corvette servo's, and the stall of the converter buys it a bit of time.

I am hoping to get the 4L80 before I am sweeping it up.

[Ziegelsteinfaust]

Originally Posted by burnin oil

I love short stroke motors that wind out but I will tell you to forget it right now. Without spending stupid money the pistons are gonna be 11:1 high octane lovers. The heads will work great up top but will suck down low. The combo will need a cam that breaths to use those heads. Total picture is a fun motor that idles miserably and fouls plugs. Running WOT will be a blast but anything else will suffer along with the MPG. It's up to you but I wouldn't do it especially considering the low torque and the weight of our trucks.

No offense on this if it sounds wrong. I think you want a style and truck that roasts tires. Mess up the rear suspension and see what happens. Pull the shocks and drive it. If it spins then add a soft shock that you can tune enoughnto limit axle wrap. If nothing changes add stiffer shock and see if traction is lost. Drag racers spend countless hours reducing wheelnspin so an on doing the same ad you reduce the process. Have you tried raising the tire pressure? Let's be honest, rehearing again is cheaper than another motor.

Yes I want a tire roaster, but the truck is supposed to be rally cross like. They don't have truck classes usually, but more of a way for me to have fun. Plus there are lots of dirt roads over the mountains I can play on.

The 4.88 gears were chosen because I intend to go with a low cubic inch short stroke engine, and rely on rpm more then torque for speed. I was very surprised that with the 383 it would not kill the tires.

I don't need 8000rpm, and I intend to keep redline around 6500rpm as it keeps part cost reasonably low. The 302 I am leaning towards would work great with 4.88's, and play nicer at 3000-3500rpm then a 350 especially a 383. At cruising speed, and not effect speed to much.

I am fully aware regearing is cheaper, but like I said in other post atleast. The engine was a stop gap when I killed the original motor. The 383 will be replaced with a engine I decide compliments my 4.88's best with the tire combo I eventually buy when I do the suspension build. Other parts of the build namely tire height, and suspension mods are in flux. So I need to decide on where I want to go next, and gather some parts. Then engine will likely be after all other planned mods so I have an analog to judge where I want to take the engine combo first.

To understand what I am trying to do look up rally cross races. Or if you watch Roadkill. The Muscle truck shoot out first 1/2 is what I am aiming at. It is not about monster power as your ability to slide the rear end around faster then you can control on dirt is alot easier.

[kwmech]

Originally Posted by Ziegelsteinfaust

It's a level 2 with Corvette servo's, and the stall of the converter buys it a bit of time.

I am hoping to get the 4L80 before I am sweeping it up.

Good choice

[Ziegelsteinfaust]

How bad or good are the th700/4L65 family in your opinion?

Personally I have never grenaded one, but have seen plenty of people I was familiar with grenade them. Sometimes multiple versions built to level 4+5 stats by well known shops.

My is a th700 with 4L65 parts, Corvette servos, and a HD clutches. I removed the lock up feature to remove quite a few pounds of rotational weight., and went with a 2500rpm stall.

The only other "th700" I had was a 4L65 in my 07 GMC rcsb, and it survived perfectly my occasional b.s. Where my other friends were going 4L80 because they were on there 2nd or 3rd 4L65, and running the same basic combo I was. Doing no more b.s. then I was. I had a 4.8 with a LS6 cam, and full bolt ons.

Now I have a 100 more hp/tq going to it. Although in a much lighter truck by atleast 750 pounds. Maybe more, but I have to visit a certified scale to get a real weight.

[kwmech]

I am in the truck and 4wd industry and have seen carnage even with 'built' 700s. They will hold together, but not with constant hard useage. They start fading away after about 40-50k miles, then you're up for another 'built' unit. They just don't seem to go the distance with real truck use such as a larger HP output or any type of towing distance, it is not really a 'truck transmission' in my opinion. I went through 3 of them when I had my 1990 suburban. The factory unit started giving out at about 140k miles so I went with a 'heavy duty built' unit because I was towing stuff for the shop to Moab and such, plus my travel trailer occasionally-- lasted about 25k when it started not wanting to shift correctly and slipping. So I a said screw it and just bolted in a Factory GM replacement with a national warranty. About 10 months later I sold it. Plus there are numerous other stories with customers vehicles.

[layinrocker65]

I’m confused as to why you are building a drivetrain around a set of rear gears. Step away from the TV and build what works, not what you see on TV.

[Ziegelsteinfaust]

Originally Posted by layinrocker65

I’m confused as to why you are building a drivetrain around a set of rear gears. Step away from the TV and build what works, not what you see on TV.

It is a way to do it, and it works if you can commit to it. Both personally, and financially. In my case it is 3000rpm at 75. To which I am perfectly fine, and enjoy the instant power. Today I drove 150 miles to see family, and I was perfectly happy.

I wouldn't do this to a Suburban. Which if I had one would be built as a mile muncher.

Just like if you choose a 468 big block, 6.2 LT series, 350 sbc, and or anything else. It puts power down at X-rpm, and carries this far. Factor in trans, and tire choices. Then you can decide on where you want it to run.

I have a set of goals, wants, needs, and hopes. Some will work, and some won't. Adjustments will be needed to keep dialing in my goals in. So I laid out my desires, and did a few different flow charts. This will be the ultimate expression of several C10's, and C20's I have owned.

When I decided on 4.88's I more or less bought into the concept that a short stroke engine would likely be the future. If I was dead set on the current 383. I would of likely went went with 3.73's, or even kept the 3.42's. As it could carry the one tire fire for 150 foot easily before the truck was getting out of shape. I wanted a Tru-Trac, but they are or were according to Detroit. 6-8 weeks out for my axle. It is not that the 383 is a let down power wise, but I could build a engine to match the truck better. Then put the 383 back in my Camaro which I already set the parts up for.

[68Gold/white]

Yeah,Frybuurger spends other folks’ money, way easier for him, than all of us.

All the comments about what you see on TV, used to be all the stuff you read in magazines.
Fryburger came from the magazine world, go figure.

I am envious of him and Finnigan, living out Hot Rod dreams!!

Fryburger just bought a late model Mopar of some kind. My interest in Mopars is a ZERO!!!

[burnin oil]

Funny. I am a chevy guy through and through except for the diesels. Most of the cars I would buy are mopars from the 60s. Guess it's a good thing that I am a truck guy.

[SunSoaked]

This will fix it.

[kwmech]

That'll certainly scatter a 700r4 in nano seconds