Changing rear end ratio's???

[kingman]

Hi

Right now l've decided that the only modification that is worth while, is changing my rear end from the so called performance rear 3.07 to a 3.73. This will give me quicker 0-60, and lose approx 2mpg and my top end will come down, which l will never reach anyway.

Even though l've seen ads for a 3.73 for appro $1300 plus labor, what could the labor be.

Or do you have a better idea. I want to do this before the summer is up.


What do you think??

Alan

 

[Ken]

Judging by the fact that you say you have 3:07s to begin with, I assume you have a manual transmission. You'll love the 3:73s, but if you have the ZF 6-speed, 4:10s (4:09/4:11) are an acceptable ratio as well.

The 3:73s with the ROD 6-speed that I am running (off the shelf ratios) are almost too much gear; I am banging second almost right outta the hole! :eek

It is nice to have the overdrive though.

_ken

 

[vader86]

No he has an Automatic, if he had a 6, he'd already have 3.45s.

I dont recall anyone stating exactly what their labor was, maybe $400-500?

 

[kingman]

Your Right!

Hey Vader

Your right l have the auto with the performance rear. At least they call it the performance rear.

l saw an article that said you can change your gears by changing the rack and pinion, is this right?

They also noted a specific Dana rear, how do l find out which Dana rear l have?

Am l on the right track or is this just mental masturbation??????????????

Alan

 

[vader86]

automatics have the Dana 36 rear

as long as you have a ring & pinion for the D36, all you do is swap it in

but if you upgrade you should seriously try to find a D44 rear, its much stronger than the 36

 

[kingman]

Thanks

Another good answer from the dark side.

 

[Harry1987]

New Gears

I just had my gears changed from 2.59 to 3.54 in my 87. I bought the gears from Summit for $319 and had them installed with new bushings and seals, new side shaft U-joints (4X) along with speedo gear correction for $1050.
This has obviously made a big difference. Its apparent though that I need a new chip. I shift out of first early and my upshift light comes on when I'm already in overdrive.
I went with the 3.54s because I already have a shift kit that chirps the tires in second without trying and in FL there are major afternoon down pours

As far as switching to a Dana 44 I've heard its not a straight swap out but requires other mods (exactly what I'm not sure).

 

[Vettelt193]

automatics have the Dana 36 rear

as long as you have a ring & pinion for the D36, all you do is swap it in

but if you upgrade you should seriously try to find a D44 rear, its much stronger than the 36

I am pretty sure autos with the performace axle come with the Dana 44, so all you really need are the gears.

 

[vader86]

Automatics with the G92 performance axle DO NOT come with a D44. ALL automatics are D36.

They only made a slight change to beef up that D36 starting in 85, but its still a D36.

The performance axle just triggered a lower gear ratio in the rear, like 2.73 or 3.07 for automatics, and in some later years the 6speed had an optional 3.54 gearing as opposed to the standard 3.45.

Its basically a worthless code, since you can order the ratio specifically.

 

[warren s]

I was thinking of the same change for my 95 LT1.

I drove a friends 94 that has 3.73s and it feels faster if you punch it from a roll, but at the track it actually goes slower because now without the ASR on it will spin the tires much more than with the 3.07s. His car now runs a 13.65, my best was a 13.45.

I guess with slicks or better street tires it would be a differnt story, but for $1300?

 

[vms4evr]

I was thinking of the same change for my 95 LT1.

I drove a friends 94 that has 3.73s and it feels faster if you punch it from a roll, but at the track it actually goes slower because now without the ASR on it will spin the tires much more than with the 3.07s. His car now runs a 13.65, my best was a 13.45.

I guess with slicks or better street tires it would be a differnt story, but for $1300?

You have to learn how to drive the car again and you need to have more control. With the 2.59s I could just mash the pedal and go. I'm happy with the 3.54s and can run it without ASR with little wheel spin off the line. It pulls significantly harder. It's great for Solo II autox. I can run 1st and 2nd and have a blast. That harder pull those gears have also allows you to throttle steer more because you can get that LT1 up in its power band. That engine rocks above 4,000rpms. On the 1/4mi drag strip I've heard a number of people say they dropped 1/2 sec off their times over the 2.59s. That's a pretty significant improvement.

And yes the $1300 is a little steep. I spent about $900 for gears, master install kit (new bearings and all), new speedo gears and sensor, and labor. The parts were all of $500.

Graham

 

[warren s]

I could see you getting a 1/2 second gain going from a 2.59 to a 3.73 for sure.

I have a 3.07, would like to go with a 3.73. I guess for best results you need some better tires or street slicks at the track.

 

[vms4evr]

Warren,
Yeah you need good tires for sure. My SZ50s are now down to racing depth :L They are still good enough for a couple more autox events but would not be so great for drag racing. When they were new though they were very sticky and didn't break loose very easily. You'll have to practice with the launches until you get the right balance.

Oh, and with the ASR off watch out for when the car shifts from 1st to 2nd. On my 700R4 it will almost go sideways with worn out tires... With good rubber it just jerks really hard and barks the tires. It'll put a smile on your face though

One caution. I'm not sure with the Dana 36 rear that you would want slicks on the car. It may lock up really well but the strain on the rear will kill it in a fairly short while. When I got my gears done the guy told me I should convert to a Dana 44 if I was going to get into doing a lot of drag racing so I didn't blow it. For occasional trips to the strip he felt it should last.

Graham

 

[WhalePirot]

I agree with Ken on the "too much gear comment".

I have the 3.73s in my 406ed '84 and wish I'd have looked harder for a mid 3's; perhaps a 3.45 or so.

The stock engine did not rev enuf; the new one fries the rear tires like crazy.


Mike

 

[vettn94]

Kingman, be happy it IS the performance ratio, I got a 2.59 in mine -lol When I went from 2.59 to 3.54 I dropped over 1/2 sec off my ET while gaining 5mph, my times went from 13.80's @ 101 mph to consistent 13.20's & 30's @ 105.5/105.9mph.
I like the mid 3 series gear but in your case maybe the 3.73 is the way to go. 3.73's may be too much for an 84' but are good for a 96 w/ the LT1.
I chose the 3.54 mainly because the 3.73 supposedly puts a little more stress on the Dana 36 but also on the advice/experience of a good & very knowledgeable friend who has been racing for many years.

Switching to the Dana 44 would be a good idea but will obviously cost you more. To answer Harry1987's question it requires changing the driveshaft (although I have heard some people argue this), differential cover, & Tq. Tube.
I paid around $1200 for a complete Dana 36 rear differential (no core reqd) with all new parts. I priced out a D44 and it was around $2200 (w/ driveshaft & cover). Of course you could try to find one used with low miles on it but your're still going to pay about the same as you would for the D36 with all new parts in it. Tough call, you have to figure out what's best for you and if you want to gamble on buying somones used parts.
Deciding whether to spend the extra cash on the D44 depends on how much your car will see the track. I only go about 4-5 times a year.
Whatever gear you decied on get some drag radials, you're gonna need em.

You know I just noticed you're out in New Jersey. If you go to Englishtown, Raceway Park look for a couple guys out there, John Panuzzo and John Mackey. They both have red 95-96 coupes and race out there regularly. It would be worth a drive out there some weekend to talk with them. Those guys know thier **** and will set you on the right track