Hey guys went to the track yesterday hoping for a new best. NOT , LOL. I changed the rear end over the summer to a Strange 60 with the same gear. The car went a little over a full tenth slower. All the way across the board. 1.44 60' time compared to a 1.41 last time I was out. 102.9 MPH compared to 104.8and 6.62 compared to a 6.51 . Is the weight that big of a deal ?? Dang I hate to go backwards .

I made the swap from 8.75, never seen anything on an ET slip.
Know of a number of others as well. Zero difference despite the extra weight.
I would be surprised if the tenth is rear end related

What were the weather conditions....The same as the time when you ran before?

Mine performed exactly the same to the hundredth.

Does the Dana have a spool ?

I assume the previous axle was an 8-3/4, did it have a spool ?

First time I have heard of someone slowing down when switching to a Dana.

It certainly was not my experience.

Possible brake dragging issue???

Thanks guys , The weather was decent yesterday but not as cool as back in March , A little more humid but dang a full tenth ?? I have a spool in this rear end also and I really figured it would still be close. Changed carbs from my trusty Biggs 950 HP to a pro systems 950 and saw 1/100 difference. Everything else is still the same except for my 1" Wilson spacer. I really thought that would have helped.. Are different tracks really that different ?? Went from Richmond Dragway to Colonial Beach. Them boys at the Beach were flying .

I bet the weather has some to do with it...You said back in March...

Oh I agree 100% and I know that day was perfect but over a 10 of a second is hard to take. LOL I am going back and check my shocks and suspension . I sure hope I can at least find where I lost it. Hopefully when I go back out it will be better news. Thanks everybody

I too hate going backwards, but lets start with all the basics...

So no where in here are the specs to compare....Did you go green bearings to green bearings? Did you go cone style posi to spring style posi? Brakes, same brakes, did you set the gaps? Pinion angle, where the perches installed the same? Running Caltrac's and leafs? All of these are variables....Are the gears pre-lapped as a set or are a set of those Richmond ones that wants you to do it while driving it?

Here is my take on it, there are a lot of variables here....Not just the weight. We have switched our cars from one to the other, and seen almost no difference, but ours were usually with a spool and wilwood brakes going from a 8-3/4 that already had a brace and green bearings, long studs etc..Somtimes with new shocks depending on how everything lined up. Generally we have had zero change in ET

If I had to bet, I would say you don't have a spool in it, and it still has drums on it. both of those need time to break in....A 1/10 and 2mph are pretty dramatic change...Take a look for maybe one drum rubbing or even tire rub, or somthing with a shock binding...re-tighten everything and go over it good. You might find somthing.

thats the same on my friends roadrunner we had switch his back and forth a few times and it looses 1/10 every time and 1.5 mph.

Dragula , I have green bearings on both rear ends, Both have ladder bars with the right pinion angle. Same Strange Shocks and Heck I even put about 20 miles on the rear end on the street. I did notice it was a lot harder to spin the rear end right after I put it in the car but I haven't checked since I have driven it. The car lost .3 one hundreds right from the gate. and that MPH difference worries me. I know I have a much better rear end now but dang spending a ton of money to go slower sucks.

I wouldn't be so fast to blame the rear end swap just yet. Different track, different weather, different carb. Same weight lube?, Brakes dragging? Gears and bearings will loosen a little as they get more passes. Does the r&p setup look good?

Did the housing bend when the ladder bar brackets were welded on?

Even if it actually is slower it won't cost as much time or money as an eventual broken 8 3/4 especially if it also takes out the trans in a spectacular fashion.

I had spider gears come apart and kill a transmission before so I know all too well the need for the change. I made my own jig and never got the heat too high when I welded the new brackets on.. Good questing though. Hopefully with a few more passes on it it will come back into the 50s anyway. It just stunk expecting one thing and going backwards. Nothing ever works like it's supposed to without a lot of effort I guess.

You can EASILY move ET around by a tenth because of weather.

My Dad (dvw) runs Nostalgia superstock. That car has to run 9.25 index at every race. Wide open it's been 9.00, and two weeks ago in bad air it would only go 9.25 wide open.

So good air to bad, we've seen it move a quarter of a second.

I've seen .30 + E.T. and 3.+ MPH loss with changes in weather from March until mid September in SO CA at LACR years ago, from 2500 density altitude in march to 7700 Ft. density altitude in September
On your deal wait until you get similar weather, temperature, humidity and barometric pressure at the same track to what you had in March before fixing anything else
Dana 60 usually hand push easier forward and backwards than 8 3./4 do in my cars that I have switch to

Thanks guys , I may be just getting too excited like you say. The weather was good yesterday but not March weather. I am going back to 100% sames as the best time it ran and see where it goes from there.

Moving from 8.75 to Dana didn't change my ET or MPH.

never slowed down, also didn't break anymore rearend parts!

I have been wanting to step up to a Dana for a long time. It sure is Purdy under my car too . I hope I can get that performance back but if I don't I know I can spray my way into some numbers without worries of carnage. I am ready to try a little N0S on the car pretty soon.

How is it possible to add weight to a car and not change something.

If your reply is "because of adding weight to the correct place", then that means if we could add the entire weight of the car to that perfect spot we could get unlimited acceleration?

If the answer is more efficient, then why aren't al rears constructed that way to save on gas?

How does this work?

There may be about 30-50lbs difference which can account for .05 in ET, but the efficiency of a Dana 60 over an 8 3/4 seems to normally makes up for it. I know a few Stock class racers who have switched like you and have seen no difference. But they do normally readjust the overall car weight back down to near class minimum. Of the most popular rears, a 12 bolt is most efficient while a Ford 9" is the worst. I would guess that GM 10 bolt may be more efficient, but it wasn't in a detailed magazine article I saw years ago.

For those reasons, I installed a Dana 60 in a low 12 second Aspen wagon. I'm confident that I didn't lose any overall ET, but wasn't able to establish a baseline and get more detailed info because of ongoing Thermoquad tuning issues.

Track timing can vary also. I've been to tracks where the difference in front tire pressure was 50+ at one track and 28 at another to get the same RT's, and possibly RPM adjustments too!. That's just the starting line. 1/8 and 1/4 mile can be a bit different too.

My dad swapped from a 8 3/4 to Dana 60 in his duster back in the late 90's and lost a tenth. If I recall correctly both rears had a posi and he used the same brakes on both. I don't see how adding weight to your car won't slow it down atleast a little.

Being you ran one track in March and another in Sept, that could be a HUGE difference. I know racing difference tracks even on the same weekend can produce difference results. Not typically a tenth difference, but there will be subtle differences. One timing system could be 1320.1 ft and one could be 1319.9 ft. My dad raced late weekend and again yesterday. He was .05 slow yesterday in the 1/8 compared to the weekend before. 60ft was the same but was down 2 mph...air wasn't real great yesterday.

If I’m not mistaken Richmond is shorter than the Beach. That said you changed a lot of things, temp is different and traction is bound to be different between tracks. Way to many variables. We would go to the Duck, Beach and Manassas and never ran the same number. Also that spacer can make a big change.

Wait another month or so and try again. I've seen 3+ tenths and 4 mph change from good air to bad summer air.
My car wasn't affected at all by the switch to a Dana from an 8.75...except it doesn't eat ring and pinions anymore. I made the switch back when it was a mid 10 sec 3700 lb car FWIW.

Hopefully I can find my numbers again. Darn shame I don't race anymore , I just chase numbers . looking for that new best. There really is something wrong with my brain. LOL Putting the Spray on it now "100 Shot" just to try and find a little more ET.

200 shot is easy and fun..

Why not race anymore.
You can just as easily find out how fast your car is even bracket racing.
I have my foot to the floor in time trials.....i am chasing numbers.
Then i put a dial on it, and if my competitor goes red, i chase numbers again. 98% of drag racing to me is beating the other guy.

I agree with you, but I think we're becoming the minority anymore.......seems nowadays most are chasing the "whoomp-whoomp" at the end.

Tracks make a difference. Capitol and VIR are at least 1 tenth faster than other tracks I have raced at here in Maryland.

Got bored just chasing numbers. I like the challange of bracket racing. Either setting it to go on index by slowing it a bit. Or running it flat out with a dial. It's ll about turning on the win light and going rounds for me.
Doug

Doug.... you going to BG this weekend?

No, I'll be at Milan for GLSSA. 1 hr drive and $2K to win. Next weekend NMCA at Indy
Doug

I really enjoy bracket racing too, Just suck at it. LOL . These guys that can cut .00 lights right off the foot brake and run dead on there number are tough to run with. I have turned into a 1st round duck a lot over the years. It is fun to go rounds, I think . It's been so long since I have.

We just put a dana in a 318 dart after if killed a ring and pinion on the 8-3/4, with around 60 passes. Best et was 7.21 at 94mph. Put in Dana 60 with same 4.10 ratio and went 7.12 at 94mph. So................