I just installed a Tremec TKO with a 5th gear overdrive ratio of .68, which I cannot use with my 3.07 rear. I am looking for a 3.55 or 3.73 rear ratio for my car. I have a 2.72 rear from a stick shift car as a spare; the 3.07 that is in the car I believe came from an automatic. Here is my question. It was my understanding that the stick-shift rears were DANA 44's, and the auto-trans rears were DANA 36's. Thus, it's safe to assume the DANA 44 rear is the better candidate for a gear swap/rebuild, right? What differentiates these rears. Are the ring gear diameters the same? Is the posi-carrier in the DANA 44 stronger? I know that the u-joint yokes are different; what 1980-82 years/tranny style, used which yokes? I remember having to swap side shafts when I put the 3.07 in. If I had the 3.07 out of the car I could look inside and answer some of my own questions, but I am deferring to the experts. Which rear would you rebuild? Whose gear set would you use? Joe Heff on Heffernan and Kaiser race fame always does my rears, so that is not a problem. On the other hand, I could simply use one of the rears as a core with a turnkey manufacturer; who would you recommend? Thanks for all your help.

 

They're all Dana 44s. 80 & 81 manual and all 82s have 1350 u-joints. 80 & 81 automatics have 1330s.

 

You getting the C4 rear mixed up with the C3. All 1984 C4's had Dana 36's, and from 1985 on all Auto Cars used 36's and all Clutch Cars used 44's.
As stated above there was a diffrence in the C3 Dana 44 1/2 Shafts and U-Joints. To switch from the 1330 to the 1350 U-joint the Yokes, 1/2 Shafts and Axel Flanges need to be changed. Sounds like You all ready went threw some of this.
I'm curious why You car won't pull 5th gear down the Highway? Do You have a small CI Engine with a lot of Cam?
Depending on what You plan to do with the car a popular swap is to install the Iron Pumpkin onto the Aluminum Batwing. However as long as You are going to only use Street Tires and stay away from Slicks I really don't think this is nessisary. However with 3:36 and 3:55 ratio's being avalable they might be an option to try out and see how You like it before spending all the Money to have a Rear end Built.
I have just the oposite issue, I have 3.73 Gears, a 400 CI engine with good torque and I need to switch to a 3:36 or 3:21 ratio.

 

Thanks for your input. I knew there was something regarding the Dana 36 rear with automatics. Thought it applied to C3 Corvettes also. I am running a 427 Tri-Power, and it does not like being lugged down to 1400 RPM at 70 in fifth. With the overdrive ratio of .68, my 3.07 is only a 2.08 ratio. That is even low for a modern technology fuel injected car. Even a 3.73 would only yield a final drive ratio of 2.54. I used to run 4.11 gears with direct drive in the old days. I am hoping 3.73's would be enough gear given the cam.

Yes I have already experienced the need to change out the drive yokes when I went with the 3.07 auto rear. I am playing a balancing act in that if I select my rear gear to work with my .68 overdrive 5th; I will render my 3.27 first gear useless for the street. That is why I am thinking that the 3.73 gear is a good compromise. I have not heard of swapping the iron pumpkin for the aluminum. Does it attach to the aluminum cross-brace? I am sure the cast iron case is less prone to distortion. Are the iron pumkins made by Dana; are they the same 6 bolt differential cover?

I know the rear is the weak link. I am running 285 40's x 17, and they go up in smoke all the time. If I was hooking, I know that puny rear would not hold up. I run DANA 60's in all my other cars. Can't do it with the IRS.

 

I have the stock 3.08 ratio in my '80 with a .67 5th gear (Keisler RS500). It's PERFECT for cruising on the freeway.The 3.37 1st gear is a big improvement over the original BW Super T-10 too.

 

There is something wrong here. Lets say that Your rear is really a 81 Auto and has the 2.72 Ratio. With a 285 40 17 Tire at 26" and a .68 overdrive You should be right around 1700 RPM at 70 MPH. If you have oval port heads and only the center two barrel carb working at cruise I would think it would work.

If your TKO is a 600 then I think You have a 2.87 1st gear.

Try the search feture at the top for lots of info on this site on installing the Iron diff in the 80-82 car. You should be able to find pictures and step by step on how to do it. It can be done useing all factory parts. All but two of the bolts line up with the Aluminum Batwing. Some Iron Diff suspenson parts are needed to be used as well. The control arms and mounts.

I like Randys Ring and Pinion the best for any RPM Calculator I have found on the Web.

 

You are right on the RPM calculation at 1700@70MPH. The problem is that in real world I can state that the engine does not like being pulled down that low. When you have a cam with 264/269 (duration @ .050), they are cranky at that RPM. The Crane Cam Catalog has a recommended cruise RPM of 4400 for this cam. That is why these 427/435 cars came with 3.73 and 4.11 rears from the factory. My effective 2.08 rear ratio (3.07*.68) just does not cut it.

I do have the 3.27 first gear, purchased specifically to try to make the combo work with the 3.07 rear. If I had known I was going to have to go with 3.73 or lower rear, I would have gotten the 2.87 first gear 5-speed. In any event, I would like to go with 3.73. Any recommendations on who works on the 1980-82 pumpkins. I have read that some rebuilders do not touch them. I have read the Trackdogg does. I have sent him an email.

If it is stronger, I may go with an aluminum/iron hybrid. We will see. Thanks for your interest.

 

Aluminum Dana 44 is much stronger than anyone thinks, I have a 30 year old stock unit behind my 427ci that sees over 500ft/lbs of torque whenever I take it out.

Do a search and see how many topics say "Blew my Danna 44" or similar, personally I have never seen one

On the other hand I seen C5's and C6's ruin a night at the dragstrip by leaving 1/4 mile of oil from a blown rear end

 

You must have an interesting Car, with a Late C3 with an Old School Engine. I can see that the Square Port Heads arn't going to be lugged down the Highway.

Toms Diffs in Idaho would be a good sorce for parts as well a rebuilding the Dana 44 as well as trackdogg.

As you allready mentioned You may trade one gear for the other by changing the ratio, 1st for 5th. It may also make the Trans weaker doing this, as I would think any trans would have the lowest gear the strongest, and the top gear the weakest.

 

I made the same mistake going with the .68...... It's nothing but a commuting gear....

But I think the better option to a new rear, (especially since I love my 1st and any lower rear end gear would be not useable.... I would have to start out in 2nd.) would be to change out the o.d. gear to the .82.... Which is what I plan on doing when I pull the pos tko for a synchro upgrade so the pos will shift worth a darn above 5k rpm.

 

A synchro upgrade will help, as will upgraded blocker rings, but it won't totally alleviate the shifting issues above 5K.

 

You put a lower 1st gear in any transmission and it will lower the torque and HP rating even though it's the same transmission.

The TKO 500 has a first gear of 3.27? and rated at 500tq and the same transmission is called the TKO 600 with a higher 2.87 1st gear and is rated at 600 tq

 

Sorry, have been away for a couple of days. I appreciate the input. The Tom's Differentials and Randy's Ring and Pinion were great leads, and I had received a call from TrackDogg (Mike) that was very helpful. Simultaneously, I found a rear which I bought from a board member "80Vette21" which I took delivery of yesterday. Thanks for the great packing job Kevin. This is a 3.73 rear and will be installed and up and running shortly. I will happily update this post to let you know if the ratio worked out. I am still concerned about effectively losing first gear. My new effective first gear ratio will now be equivalent to a 4.88 rear with a 2.54 Muncie wide-ratio trans. I will let you know.

 

Hey Ratking,

Thought I'd blow the dust off this thread and see if you've made the progress you mentioned in your last post. I'm in a similar boat as I did a frame up on my 69 with the TKO-600 and have the original 3.07 rear end. I've been kicking the idea of a 3.73 around and wanted to hear your feedback.

 

I think the biggest ring you are going to get into the 80-82 housing is 3:73 at least that is what I was told when I went looking for 4:11's

 

Hi Guys,

Long overdue on an update. The rear I bought from our fellow club member has been in the car and performing wonderfully. My fear about losing first gear was unfounded, and I am finally able to use overdrive. It is a perfect combination. It would work great with your TKO 600. I have the ability to glide through cruise nights in first with the engine sounding awesome through the side pipes, without getting on and off the clutch. It launches fantastically, and I can actually use fifth gear.

While it had no bearing on the original posting, I have to give everybody an explanation of what I actually have. I have a 1962 MGA sitting on a 1982 chassis with a 427 Tri-Power under the hood. We shortened the chassis to the wheelbase of the MGA, and widened the MGA body 11 inches to sit on the shortened but stock width Corvette frame. The car looks and sounds like it is on steroids, and it eats VIPERs.

The chassis, suspension, brakes, and drive-train are all vintage Corvette. In a way, it looks like a Cobra, but it sure ain't no FORD. It's the fastest British roadster on the street. This isn't a kit car, but a true labor of LOVE.

If nobody is offended, I could try to post some pictures. I am a many time-over Corvette owner, this MGA just happens to be the latest project. Been on the road for over 18 years. With my new found enthusiasm with the cars drivability now, I am dropping in a 502 Rat. Car weighs 2500 pounds; should be fun!

 

As a lifer here I'll say, oh heck yeah! Would love to see what you've done. Thanks for getting back so quickly about the rear end. I had a gut feeling about the 3.73 and am having the same experience with my 3.07... 1st gear feels like it should be 2nd and 5th gear dogs on the highways. I'll keep an eye out for the pics! Cheers! Scott

 

Please post pics.

 

I have a whole book of the build, and some recent pictures of the car at the Wings Field plane show. I have a few under hood pictures too. Apparently as a junior member, I cannot post the pictures directly. If some-one would contact me, I will gladly forward some pictures to them; rat_king@verizon.net . Thanks.

 

I love my TKO 600 with .64 overdrive. Of course the .64 OD is used on the highway only to get you to the dragstrip. I run about 1,800RPM @ 80 mph which I love and the fact that I am within supercar range for 0-6-mph ( just leave it in first gear ). I have a 3.08 rear end and blow through the traps in 3rd gear @ 121 mph with a granny launch and spinning the tires to about 3/4 track.

So if I were to have a bullet proof rear end I would hooking up and going down the track properly I would be getting some pretty decent ET's. That why I'm waiting to see if tracdogg2 can come up with a 12 bolt rear end. Nothing would make me happier than to be able to launch the car correctly and shift all the way down the track. I hope tracdogg2 is still working on it, last I heard a week or so ago he said it was possible

The .64 overdrive was invented for cars with with rear ends in the 4.11 range to be able to drive their cars on the highway to the track. The .82 is a road racing tranny as it will give you a higher top end depending if you have enough power to pull it.