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!