Qkslvrc5z

Probly a very common topic. But I'm wanting to change my ring and pinion in my c5z. I want it to be fairly streetable but that isn't a huge concern for me. Car is mainly a weekend and strip car for me. I'm running a 26" bias ply at the moment for the track. And have bolt ons. Will be going heads cam intake soon and can go to a 28" tire of needed. But may also put a 150 shot on eventually.

Thinking 3.90 is my best option but was hoping to get some opinions from those who have used a 3.73, 3.90 or 4.1 with similar set ups.

Thanks in advance.

Sigforty

I had 3.90s in a heads and cam setup. I eventually pulled them out and went to 3.42s because I added a bigger motor and nitrous. The 3.90s were nice, but almost made 1-3 unusable on the street because I had to shift so fast.

Qkslvrc5z

That's another concern, I would like to go to an ERL 434 Ci motor one day. Would I be better with just a 3.73 then?

Stroker87

I swapped to 3.73 and very happy

before with the 3.42 gear the car felt sluggish and was able to feel it hit the power band now its in the power band when every i lay in to it, car feels so much better all around every gear feels better, 26" tire 80mph is around 2k rpm, shifting is a little faster but not bad. traction has become an issue on street tires will light up 1st and 1/2 of 2nd power shifting 3rd it sways out like you are shifting in to 2nd and power shifting 4th gear it brakes loose to

really surprised since it was a small change in ratio's how the car came a live, i'm just a bolt'on tuned car with monster stage 2 and rpm level 5 trans and the 3.73 making 38xrwhp 367rwtq

Qkslvrc5z

As of right now I have a bolt ons tuned c5z. Car leaves sluggish, bogs the motor on 26" bias plies at the track. I run a 28" drag radial on the street and it dead hooks in 2nd unless the roads cold.

I'm going heads and cam soon, but for now I'd like to get a real good pass in on the slicks and skinnies.

dbgoodwin

Sounds like what you're saying is that on the street my bolt on stock gear z06 will walk away from you from light to light. I like traction too much for that!

Stroker87

maybe not! I am able to drive it pretty decent and manage it but if i was to just go all out then yes a good chance of it

Qkslvrc5z

What kind of 1/4 mile times are you guys cutting with your bolt ons cars out of curiosity?

Sigforty

The 3.73 might work out better. You really need to go find a calculator and look at what the top mph would be in 4th if you drag race. Changing tire size will also impact that. I still run the 26" tall tires with my 3.42s. If I gain more power I will go up to 28" tires. As my car is setup the top mph in 4th is around 142 mph. That is based on my engine specs, tire size, rear gear and trans.

Qkslvrc5z

I have checked the calculator, with a 3.90 and 26" tire Id run the top of 4th around 135 @ 6800 rpms. About 142 with a 3.73, same tire and redline. I would be willing to go to a 28" bias ply for the track if needed when making more power. I really want to do the lg spindles to run 15s also.

Varmit

I had 3:90's in my C5 with head and cam package, it hauled the freight. Then installed an LS2 that was a stroked 402 with a Vortec T TRim 705 at the wheels and with 3'90's is was insane crazy. Smoked the rears at 100mph in 4th without touching the clutch!!!!!

Qkslvrc5z

My next build will be either a 434+Ci motor or a 416 with an f1c blower. So I'm trying to leave some open room. Most likely I'll end up with a 440ci ERL motor with ported ls7 heads and a solid lift cam

dbgoodwin

And I'm sure at the strip that setup isnt bad at all. Many people get way too ambitious with the go pedal though. I think 3.90's with the m12 would just be wicked short

Qkslvrc5z

I agree, really starting to lean towards a 3.73, so it's not so short.

Sigforty

The 3.73 sounds about right, but you may still have to change in the future. I personally am on my 4th diff. I went from 3.42's to 3.90's. I broke both diffs with the 3.90's and now I am back to 3.42's again.

Stroker87

did you upgrade the diff that you broke or just a gear swap? what kind of HP/TQ are you making?

I had RPM Trans upgrade mine to the C6Z shafts and clutches so hopefully it will be ok

Qkslvrc5z

I put the 300m shafts, and upgraded my clutches, I'm going to put a 3.73, anything else I should upgrade while I'm in there?

Sigforty

They were both upgraded diffs from DTE with hardened long shaft, clutches, side cover, etc. The first diff snapped the posi cross pin in 3 places and ate up the posi gears. The second diff I think the gears failed as numerous teeth were sheared off the pinion and ring gear. That in turn broke the side of the case and pinion support.

Qkslvrc5z

Were you running a drag radial?
I've heard once you upgrade the shafts and launch with a radial it can break other things. My brothers car made 700whp 670rwtq has a stock untouched rearend and trans and hasn't broken anything. Car cuts consistant 1.5 60fts but he runs bias ply tires.

Sigforty

Nope just the bias ply Et Streets.