98 Cobra New owner question

[Northern98]

Hey everyone,
I recently bought a stock 40k mile 98 cobra with the exception of a set of saleen replica wheels that came with it. I've watched a few acceleration videos of other cobras, stock and slightly modded, and it seems I have a lot more trouble putting power to the ground through 1st gear. If I just leave a stop normal and ease into wot through first, it still wants to break loose and skates the rear-end all the way through 1st. Not sure if I just hit the engine jackpot and have a strong stock engine, I dont believe the original owner changed the rear-end gears. Any suspension mods to help keep me moving forward? It has brand new nitto tires so they shouldn't be the issue. Definitely a way different car than the built 94 GT I used to own, even having similar horsepower. Thanks in advance for any input.

 

[98 svt]

Your built 94 should have way more low end torque than a bone stock 98 Cobra.
Id be willing to bet it has gears. Get it up on the highway. What are your RPMs at 65?

 

[Northern98]

Your built 94 should have way more low end torque than a bone stock 98 Cobra.
Id be willing to bed it has gears. Get it up on the highway. What are your RPMs at 65?

 

[Northern98]

I want to say around 2100-2200, but I'll verify that when I get back home and post an exact rpm. The 94 definitely had torque for days, but I never got to the suspension before I sold it so it was really hard to control. Told the guy who bought it to upgrade it immediately, he didnt and wrecked it the first drag race.

 

[98 svt]

Confirm your RPM at 65, also what rear tire size.

 

[Northern98]

Okay sorry about the delay, busy day today. It's at 2000 rpm at 65 on 245/45/18 tires so its gotta have the stock rear end. Maybe the bushings in the suspension are causing it? They are starting to squeak and I'm sure they dried out with the car sitting most of its 22 years.

 

[ViciousBlack97]

Okay sorry about the delay, busy day today. It's at 2000 rpm at 65 on 245/45/18 tires so its gotta have the stock rear end. Maybe the bushings in the suspension are causing it? They are starting to squeak and I'm sure they dried out with the car sitting most of its 22 years.

If you're at 2k rpm at 65, you definitely have gears. That's what my car turns at that speed with 3.73s

 

[Northern98]

Thanks for the answer! I guess I'll leave the rear end alone for now. I'm trying to wait a couple of summers driving it stock, aside from gears I suppose, before I succumb to the modification bug this time.

 

[98 svt]

That close to 4.10s as well. You could always jack it up and spin the driveshaft to confirm which gears.

 

[Northern98]

That close to 4.10s as well. You could always jack it up and spin the driveshaft to confirm which gears.

I'll throw it up on stands and verify for sure once I'm prepping it for the long sit during winter. We dont have any performance shops near me and the better of the 2 transmission shops closed down so I might as well just buck up and learn what I can about the 4.6 once the snow hits.

 

[xblitzkriegx]

2000rpm in 5th isn't a good way to tell gearing. It's too low an rpm. At that speed, the difference between 3.27 and 3.73 isnt even 3mph.

Run it up to the top of second. If it hits 75+, it's a 3.27 gear. If itll barely make it to 70, it's 3.73.

How old are the nittos? Like, the age, not the tread depth. What type of nittos? DRs? I'm leaning more towards the tires being old and dry. I can do exactly what you describe on my completely stock Cobra when the tires are dry (not bald) or when it's below about 60 degrees on summer tires.

 

[Northern98]

Would using an rpm calculator work if I just plugged in different rear end ratios and used 4th gear at 65? I tried it on a site using 3.73s and it shows i should be at 3050 rpms at 65 in 4th gear, which it was when I checked.

 

[Northern98]

Would using an rpm calculator work if I just plugged in different rear end ratios and used 4th gear at 65? I tried it on a site using 3.73s and it shows i should be at 3050 rpms at 65 in 4th gear, which it was when I checked. No idea how old they are. The guy sold it through the dealership he bought it from in '98 since he had permanently moved to Florida.

 

[Tillerman77]

Would using an rpm calculator work if I just plugged in different rear end ratios and used 4th gear at 65? I tried it on a site using 3.73s and it shows i should be at 3050 rpms at 65 in 4th gear, which it was when I checked. No idea how old they are. The guy sold it through the dealership he bought it from in '98 since he had permanently moved to Florida.

Read the date code on the tire sidewall. See here.

 

[Northern98]

Read the date code on the tire sidewall. See here.

Found it. Early 2016 so they are getting there. Unfortunately that means the brand new tires on the extra set of rims are probably getting dry too. Thanks for all the help so far, it's been awhile since I had to think beyond just driving and maintenance.

 

[shurur]

I have 3.73 and your numbers seem off
https://www.cjponyparts.com/resources/engine-rpm-calculator

65mph should be around 2100 rpm

Try this tool. Most of those tool default to 5th gear.

Edit: ok my mistake ...3176 rpm in 4th.. 1:1 ratio

 

[Northern98]

I have 3.73 and your numbers seem off
https://www.cjponyparts.com/resources/engine-rpm-calculator

65mph should be around 2100 rpm

Try this tool. Most of those tool default to 5th gear.

Edit: ok my mistake ...3176 rpm in 4th.. 1:1 ratio

Its definitely running at 2050ish rpms at 65 in 5th and their site is showing 3.73s to make that happen. I'm sure different site calculators round differently and end up a with close but varying numbers. I'm going to take it to a buddies shop once he's got downtime and we will put it on the lift and figure out for certain

 

[Northern98]

I got impatient and put it on Jack stands. Definitely 3.73s in the rear, if anyone wanted to know for sure. Glad I posted something or else I would have been a little bummed when I went to change the "stock" gears to the same thing. I'm going to try and get in contact with the previous owner and see if there is anything else.

 

[xblitzkriegx]

I got impatient and put it on Jack stands. Definitely 3.73s in the rear, if anyone wanted to know for sure. Glad I posted something or else I would have been a little bummed when I went to change the "stock" gears to the same thing. I'm going to try and get in contact with the previous owner and see if there is anything else.

Change them to at least 4.10s. 3.73 is still too long. It'll get roughly the same fuel economy on the highway and it might even pick up a mpg in town. Hell, go 4.30 or even 4.56 if you don't take long trips in it.

 

[98 svt]

Yup. As far as NA B headed 4.6 goes.....4.30s or go home.


I ran 4.30s for many years. Got 21 mpg on the highway still too.