8 3/4 center section options

[Burdar]

I'm getting close to buying everything I need to build the center section for the Dart.  I bought a cheap 741 case with a junk cone sure-grip and pitted gears.  I stripped everything out of it and cleaned it up.  I'll probably have it powder coated before assembling it.  I've got a few questions I'd like answered before I order parts from Dr Diff.  Maybe I can save a few bucks here and there...maybe not.

I've got two choices of ratios.  3.55 and 3.73(Richmond Gear) I'm leaning towards the 3.55s.  The car isn't going to be raced.  It's just going to be a cruiser so I was planning on saving $100 by going with the reproduction Powr-lok instead of the Sure-Trac.  I think that should be plenty strong for a 400 flywheel horsepower application.

When going through the checklist on the Dr Diff site, it asks if I want new ring gear bolts.  Can I reuse the bolts I have or is it a good idea to always replace them?  I assume there shouldn't be a difference in the length or thread count required between brands or sure-grip styles.

The next question is about bearings.  There is an option between "Koyo USA/Japan" and "Timken".  Is there a big difference here?  The Timken bearings are more expensive.

This next question I'll have to ask Dr Diff about I think.  The bearing kits say they come with front and rear pinion bearings as well as two carrier bearings.  However, the pics on the website only show three bearings in the kit.

Setting up gears is something I really want to learn how to do myself.  I was even thinking about bringing all the parts to Carlisle and having you guys teach me in the hotel parking lot.   Dr Diff sells a spanner wrench that fits the side adjusters.  Is this something that I should buy?  Do you adjust both sides at the same time or one at a time?  Do you need two wrenches or just one?

[Cuda Cody]

3.55 and Timken.      

[71-440]

We used Timken in the aerospace industry for years.

[RUNCHARGER]

I would spring for new bolts and Timkens. Is your core suregrip bolted together? If so I would just clean it upand put new clutch discs in it.

[Chryco Psycho]

I tend to agree , 3.55 gears & Timkin would be my first choice , But Koyo is a top quality product as well
You should have 4 brgs thoug , 2 on the pinion & 2 on the sure grip
Setting pinion depth requires special tools & a press , not so easy in a parking lot !! Because you have to either hone a brg & slide it on to get the initial reading or press it on & off without damage to figure out the shims needed , probably best left to a specialist , setting the side play / ring gear mesh is relatively easy to do but if it is at a shop to do the pinion might as well get them to set it all up & warranty it .
Ring gear bolts can be reused but remember they are Left hand thread or you can buy new .

[Burdar]

The sure grip is a cone style. The case is all ovaled out around the big pin. It's junk.



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[Chryco Psycho]

In that case Tru trac or clutch type , don't waste your time on a cone type

[nsmall]

I enjoy my 3.55's in my 340 with an auto.   3.73 sound more fun.  This car is a toy right, maybe you need 3.93 for even more fun     3.55 is about all I can handle as I do drive it on the freeway, yet I do like to punch whenever its safe.

[dodj]

Just my opinion...if it is going to be a cruiser and not competing in the stop light grand prix, consider 3.23's. They behave much better on the highway and  on a longer road trip. If you are going to be staying in town and highways are not a concern, 3.73 or 3.91. Will be way more fun than 3.55.
I think I'm in the minority, but I have always thought 3.55's don't do anything well. Not great for highway, not great off the line. 

In that case Tru trac or clutch type , don't waste your time on a cone type

I replaced my worn out cone type with a tru-track unit. Only about 1000 miles on it, but happy with it so far. Don't forget the axle plug on installation....like I did. 

[RUNCHARGER]

You're not alone. Those are my feelings as well Dodj.

[1 Wild R/T]

If you haven't already tossed all the original parts you stripped out of the case hang on to the original pinion depth shim, it'll give you a good starting point if you go with the honed bearing method of finding the pinion depth...

Back in the day you could find a +/- number inscribed on the end of the pinion gear... That was the deviation from zero on pinion depth..... If there was no number the gears were standard... With that number from your old gear & your new gear as long as the original gears were set up right you could adjust the shim to keep the same location & be safe....  I haven't seen a new gear set with the number inscribed in many many years...

The shim compensates for machining variances in the gears & the case...

[Burdar]

The sure grip that was in it was a cone. It's completely junk. I'm going to buy the reproduction clutch sure grip from Dr Diff.

The only two ratios available for the 741 case are a 3.55 or a 3.73. No other option.

I didn't toss anything. I kept all the shims and reassembled the pinion gear how I took it apart so I knew the order it went together.

I have a complete open 2.94 center under the bench as a backup.

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[kawahonda]

Just my opinion...if it is going to be a cruiser and not competing in the stop light grand prix, consider 3.23's. They behave much better on the highway and  on a longer road trip. If you are going to be staying in town and highways are not a concern, 3.73 or 3.91. Will be way more fun than 3.55.
I think I'm in the minority, but I have always thought 3.55's don't do anything well. Not great for highway, not great off the line. 

In that case Tru trac or clutch type , don't waste your time on a cone type

I replaced my worn out cone type with a tru-track unit. Only about 1000 miles on it, but happy with it so far. Don't forget the axle plug on installation....like I did. 

Not the first time I've read this opinion about 3.55s, but I fully resonate with it every time I read it. 3.55's don't do anything best, they are a compromise gear. They compromise the freeway, and they compromise the launch. I always felt it was better to "lean" one way or the either...either go 3.23 or go 3.73. 3.55s are great for stock restorations I would imagine though...Chrysler used this ratio on their performance cars.

Let's be honest: these cars were never designed to barrel down the freeway @ modern 85 MPH+ speeds. No over-drive = no modern freeway driving experience. If you want to keep up with modern cars and modern speeds, by all means, throw in 2.70s and have fun, or just live with 3.23s and be a dog off the line if you have a 727 w/ small block.

I'd rather ignore the interstate and not make the car something it's not, and instead focus on 65 MPH as my "max" cruising speed--something that I only do a few times a year and not far distance driving. If you do the math, 3.73s actually make decent for this, especially if you have 255s or larger rear tires. Most people agree that 340's are fine @ 3000-3200 for cruising speeds.

If I had a big block with a manual, I can see where 3.55's start looking good.

[Cudakiller70]

Let me help spend your money! Get one of each! OK next