rear ends

[hdff]

i'm looking for info on the differences in a chevy rear end and a dana. i'm sure the dana is better but how. i have a yoke seal leak in my chevy rear end and while it is apart is there anything i should do to improve it. i do not know what ratio it is , hope to find that out while it is open. it is being pushed by a stock 402bb and a 700r4 transmission. i am considering adding a locker to it. what are the thoughts of the knowledge on this forum? thanks

[engineer_gregh]

From previous reading from other members on the board the recommended ratio would be a 3.73 because of the 700R4 tranny. I did a lot of studying on this topic as I'm also running a 402 but with a turbo 400 and a 3.08 rear end. Great for highway speeds but not so much out of the hole with the 29" tall tires on my truck. For me, next upgrade will be 3.42 posi with a gear vendors over/under drive. From my research its the best of both, better out of the hole and good highway speed without high rpm's. To calculate rpm's I use the formula mph x rear end ratio x 336/ tire height. Example at 65 mph my RPM's are at 2319. The gear vendors over under drive returns 26% so at 65 with a 3.42 ratio I would be at ~1900 RPM's. I remember from a previous post you were not impressed with the power of your 402. I'm betting you are running a 3.08 rear end with 27" tires, slower out of the hole.

[nlped]

The 27" tall tire would be more beneficial for "out of the hole" power with a 3.08, but hurt him some on the interstate. Not as much since you have the 700r4 though. I'd throw a 3.73 (or due to the very low profile tire, if it is 27", maybe a 3.42) with a good posi unit in it. Lockers tend to suck for street driven vehicles, especially with a light rear like a truck. My Bronco had a full time locker, and while I loved it in the woods and mud, it was scary while street driving. I ended up going with an ARB for the best of both worlds, but I digress .

Use Greg's calculation and figure out which one gives you the best for your driving style.

[crakarjax]

I'm going with a 3.42 also, and my reasoning is that I love how my 2005 Suburban drives (it has 3.42 gears). I plan to update my engine/trans to the same as in my 'burb so the combo makes sense.

I have a chevelle with a 402, TH400 and 3.08 as well. It gets up and goes just fine, so if you have the torque then low gears aren't an issue!

[engineer_gregh]

Here's a decent article on the differences in 402 engines. A few typo's in the article but a good read. Regardless of torque; tire size, rear end ratio's, and transmissions make a huge difference in drivability and how the power is transferred to the pavement.

http://www.ehow.com/info_7750247_his...02-engine.html

[hdff]

if memory serves me right now at ~65 mph i am turning 1800 to 1900 with the 700R4. a problem i have to check out with a transmission shop is to see if i can get it to kick into OD at a lower speed, now it is at 62mph, i would like it to kick into 4th at 55 mph if possible. 1900 at 62 is good,

also could someone explain the difference in a locker and a posi. the preformance rear end place i am going to use to do the work recommended the locker.

[nlped]

Originally Posted by hdff

also could someone explain the difference in a locker and a posi. the preformance rear end place i am going to use to do the work recommended the locker.

I'm absolutely sure there are folks on here who can provide a much more thorough explanation, but here's a start

A locker is just that...the two wheels are "locked" together. Meaning they rotate the same direction and same revolutions no matter the conditions. Great for a straight line, but hard on tires, driveline and scary as He77 in the rain going around a curve or corner. In a corner or tight curve, the inside tire will be trying to cover the same amount of distance as the outside tire, which makes that tire either spin or the vehicle to buck (for lack of a better word), and can be disconcerting in the rain when the rearend can try to come around on you. They are great for off road conditions where it's muddy, sandy, etc. where the tendency for the inside tire spin isn't noticeable due to the slicker conditions.

A good posi unit acts much like a locker in a straight line, but when the forces of a corner or curve act on the posi unit, it unlocks and lets one wheel/tire freewheel so there isn't that predisposition to get rowdy like a locker. Note that I said a GOOD posi. If the unit is used (of unknown condition) or one of the cheaper models out there, it may not function much better than the standard open differential.

[engineer_gregh]

Here's an article I came across that you might find helpful hdff.

http://www.superchevy.com/how-to/148...?__federated=1

[hdff]

Originally Posted by nlped

I'm absolutely sure there are folks on here who can provide a much more thorough explanation, but here's a start

A locker is just that...the two wheels are "locked" together. Meaning they rotate the same direction and same revolutions no matter the conditions. Great for a straight line, but hard on tires, driveline and scary as He77 in the rain going around a curve or corner. In a corner or tight curve, the inside tire will be trying to cover the same amount of distance as the outside tire, which makes that tire either spin or the vehicle to buck (for lack of a better word), and can be disconcerting in the rain when the rearend can try to come around on you. They are great for off road conditions where it's muddy, sandy, etc. where the tendency for the inside tire spin isn't noticeable due to the slicker conditions.

A good posi unit acts much like a locker in a straight line, but when the forces of a corner or curve act on the posi unit, it unlocks and lets one wheel/tire freewheel so there isn't that predisposition to get rowdy like a locker. Note that I said a GOOD posi. If the unit is used (of unknown condition) or one of the cheaper models out there, it may not function much better than the standard open differential.

makes sense to me. any recomendations on a good posi to add in the stock chevy rearend?

Originally Posted by engineer_gregh

Here's an article I came across that you might find helpful hdff.

http://www.superchevy.com/how-to/148...?__federated=1

good info i'll have to do some cypherin on this later..... thanks

[nlped]

^^^ Auburn & Eaton are the 2 I've personally used and have had great luck out of.

I have an Auburn Pro in the 12 bolt that's going under Walt, this rearend used to be under my '87 GMC 2wd but I decided to put it under this one so it now has the correct saddles for the trailing arms. Love the Auburn...

[engineer_gregh]

Just curious what size tires are on your truck?

[engineer_gregh]

Sorry, tire size question was for hdff.

[hdff]

Originally Posted by engineer_gregh

Sorry, tire size question was for hdff.

tires are 255/70/15 and are between 27.5 and 28" tall. the rim size is 15x8 . when it is time for tires i plan on going to a wider tire and maybe going to a 60 series

[nlped]

Originally Posted by engineer_gregh

Just curious what size tires are on your truck?

Originally Posted by engineer_gregh

Sorry, tire size question was for hdff.

No worries, but I will throw mine out there just for reference.

355 sbc with TH400 and factory posi with 3.08...275/60r15=28"

468 BBC with 700r4 and Auburn pro with 3.42...295/40r20=29.3"

5.3L with 4L60e and Auburn pro with 3.73...285/30r22=29.75"

[hdff]

Originally Posted by nlped

No worries, but I will throw mine out there just for reference.

275/60r15=28"

your 275/60/15's are 28" tall?

[nlped]

Originally Posted by hdff

your 275/60/15's are 28" tall?

Yeah. Actually 27.99"

[Fitz]

Originally Posted by hdff

makes sense to me. any recomendations on a good posi to add in the stock chevy rearend?

Yup. Eaton 419.00 at DTS

[engineer_gregh]

hdff now I'm really curious as to what ratio is in your truck. Using the calculator below, you maybe running a 3.42. Are you using the stock tach as reference or aftermarket tach?

http://tri-5.chevyrides.com/rpm.php

[crakarjax]

re: posi -- I went with a TrueTrac. No clutches and so no rebuild in the future, smooth action unlike the lunchbox lockers. Also they are supposedly very tough.

http://www.eaton.com/Eaton/ProductsS...trac/index.htm