3.90 ring and pinion (available again)

[BAT]

Let's see. Tuner kit to 750HP. 3.90:1 gear set. Can you fit a large enough tire under the car to hook up?

Beware. There were a few that had the 3.90 gears with the TT setup. They later went back to stock gears because 1st gear was useless. I have the 3.90 gears as well with the 4L whipple and 1st gear is border line useless. I love the 3.90’s though.

 

[Steve Schneider]

HI BMF

Regrading the 3:90 gear, I think I understand, go from stock which is 3:30 (?) and get way more 1 st gear quick acceleration, push back in the seat power like my 67 big block mustang with 4:11? In that case good for 1/4 mile but no good for top speed on the Hi way, so since I rarely ever use top speed on GT anyway no compromise, is this right?

Thank you
Steve

 

[GT@50]

HI BMF

Regrading the 3:90 gear, I think I understand, go from stock which is 3:30 (?) and get way more 1 st gear quick acceleration, push back in the seat power like my 67 big block mustang with 4:11? In that case good for 1/4 mile but no good for top speed on the Hi way, so since I rarely ever use top speed on GT anyway no compromise, is this right?

Thank you
Steve

Correct, if you can get it to hook up, but fun trying. A huge benefit is that it'll be easier on the clutch in stop and go traffic.

 

[fjpikul]

Just FYI, MPG goes down. On a long trip that means extra fill up or two compared to stock. Ask Larsen how many times we have abandoned him on a long trip. Ha ha.

 

[B.M.F.]

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[CJ428]

330 gear was for 0-60 times, 390 is what the car needs for road course.

 

[nota4re]

Beware. There were a few that had the 3.90 gears with the TT setup. They later went back to stock gears because 1st gear was useless. I have the 3.90 gears as well with the 4L whipple and 1st gear is border line useless. I love the 3.90’s though.

Almost all of the TT builds that we did utilized an electronic boost controller (neatly replacing the GT's boost gauge) and virtually all such controllers have the capability to establish boost limits by gear. This would have been a far more economical solution than doing another R&P change!

 

[Steve Schneider]

have pulley tune now, so how does 3:90 swap compare to maybe easier 4L whipple change? Or does they compare?

 

[centerpunch]

Instead of celebrating the availability of the gearing the car should have come with (except for no-shift 0-to-60 times for car magazines), some of you seem to be——criticizing it?

Anytime someone broadens the availability of custom parts for these cars we should be thanking him, whether that specific part is of interest to us personally or not.

I had actually planned to do track events with my car and was actually fishing around for a used 3.90 gearset or tranny equipped with same, but my old brain recently regained a tiny part of its sanity and I will not be doing track events. (Been there, done that.)

But I am nonetheless happy to see this VERY-complex part become available again.

 

[PL510*Jeff]

The 3.9 conversion, by Stillen, was the best change I have made on my GT. Makes driving around town so much easier. As was said by Centerpunch - the loss of 0-60 in 3.2 seconds - not missed by me. I have about 120,000 miles going for me with the Stillen set up.

The 3.9 diff. makes gears 1-4 more of a close ratio box. Takes some of the boy racer out of the game from stoplight to stoplight. Oh, well!

 

[TO AWSUM]

Instead of celebrating the availability of the gearing the car should have come with (except for no-shift 0-to-60 times for car magazines), some of you seem to be——criticizing it?

Anytime someone broadens the availability of custom parts for these cars we should be thanking him, whether that specific part is of interest to us personally or not.

I had actually planned to do track events with my car and was actually fishing around for a used 3.90 gearset or tranny equipped with same, but my old brain recently regained a tiny part of its sanity and I will not be doing track events. (Been there, done that.)

But I am nonetheless happy to see this VERY-complex part become available again.

Centerpunch, why are you so defensive? There are always 2 sides to every story and everyone has a right to know the pros and cons of every purchase. This modification is not for everyone as the discussion above demonstrated, but it is a good option for those interested and are knowledgeable about the compromises it causes.

 

[PeteK]

Not defensive, just wondering out loud: if the car can already burn rubber in 1st and 2nd from 0-100 MPH, why do you want a higher axle ratio? It just shortens the range of the gearbox.

 

[B.M.F.]

.

 

[PeteK]

Yup, stickier tires are available now, but that just brings up the follow on question: If you want to drag race, why start with a GT? There are much better platforms for that purpose, including a couple that major manufacturers will sell to you off the showroom floor. I guess some of you want to show your taillights to Hellcats...

And Jeff, I can see that it would be easier on the clutch in Seattle traffic. Fortunately I don’t have to deal much with that in my part of WA! But replacing the clutch three or four times would be cheaper.

 

[2112]

The cars are lazy in 3/4th gear tho.. esp stock powered. Much better tires out there now than 15 years ago to get better traction in 1st and second gear.

Would it have been easier (more cost effective) to change the lazy gears out?
.

 

[centerpunch]

Centerpunch, why are you so defensive?

Uh, sorry. It’s just that IMHO the gearing for this car was chosen to optimize the numbers (by having a zero-shift 0-to-60 and a 2-shift 1/4 mile) rather than optimize the driving.

I don’t blame them for doing it that way, because numbers sell cars. All manual tranny performance cars had similar strategies, probably.

 

[PL510*Jeff]

Yup, stickier tires are available now, but that just brings up the follow on question: If you want to drag race, why start with a GT? There are much better platforms for that purpose, including a couple that major manufacturers will sell to you off the showroom floor. I guess some of you want to show your taillights to Hellcats...

And Jeff, I can see that it would be easier on the clutch in Seattle traffic. Fortunately I don’t have to deal much with that in my prart of WA! But replacing the clutch three or four times would be cheaper.

It was not a matter of cost, it was the drivability improvement that I wanted. And with 140k I'm just on my second clutch.

2112 - re-gearing was not an option way back then. Not sure if it is now either. But I'm sure that would be pricey too.

PeteK - which motor home is yours down by the river? I miss seeing the log home building.

 

[Brombear]

What would be the top speeds in 5th and 6th gear for a stock car or one mit pulley/tune exhaust ?

 

[B.M.F.]

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[GT@50]

oops,wrong area