series 4 carrier question

[steeeeeve]

Hi fellas,
I'm having my turbo400 swapped with a 700r4 soon and I have a quick question.
I'm pretty sure I have a 4.11 rear end. But it seems a little bit sloppy. (jacked up)I can spin the wheel a bit before the drive shaft starts spinning. It seems too much but I really don't have a good reference.
The question is how high of a ratio (low number) can I go before I have to change the carrier? Is there an adapter or ??? to use a 3.23?
thanks,
steeve

[steeeeeve]

Originally Posted by steeeeeve

Hi fellas,
I'm having my turbo400 swapped with a 700r4 soon and I have a quick question.
I'm pretty sure I have a 4.11 rear end. But it seems a little bit sloppy. (jacked up)I can spin the wheel a bit before the drive shaft starts spinning. It seems too much but I really don't have a good reference.
The question is how high of a ratio (low number) can I go before I have to change the carrier? Is there an adapter or ??? to use a 3.23?
thanks,
steeve

okay. looking at past threads it looks like a 3.73 before I have to change carriers. PLEASE CONFIRM IF YOU KNOW FOR A FACT
I'll only do it if my mechanic confirms too much slop in the rear end.

mild 350
700r4
28" tires
4.11 or 3.73 ratio
seems like that i'm looking for in order to cruise the truck comfortably.

2193rpm at 70mph

as opposed to

3452rpm at 70mph (current set up)


of course I could do

2587rpm at 70mph
by just changing the rear end to a 3.08 and keep the turbo400. (no burnouts in this truck/ i drive like a great grandaddy)

[cj847]

I can't say for sure but I am 99.97% sure that is correct. My question is since you now have overdrive, why do you want high gears (lower numerically)? You are "double dipping" there.

PS> If your current rear end was working fine before, I bet it is good. There is some slop in them.

[steeeeeve]

Originally Posted by cj847

I can't say for sure but I am 99.97% sure that is correct. My question is since you now have overdrive, why do you want high gears (lower numerically)? You are "double dipping" there.

PS> If your current rear end was working fine before, I bet it is good. There is some slop in them.

yes. I see what you mean. I would only consider changing from 4.11 to 3.73 if the 4.11 is shot.

If i have to replace the 4.11 i'd gladly sacrifice acceleration for better highway cruising.

[Rick Bollinger]

You will more than likely be happy with the 4:11's with the 700r4. Especially when you are used to running a 400. You are going to drop your top end rpm a bunch and still have even more pulling power off the line.

[gmc684x4]

Yes 3.73 is the top end on a truck 12 bolt diff

I liked 3.73 in my 4x4 trucks decent low grunt for 4x4
Tore apart a few 88 98 trucks most with 700r4 seamed to be around 3.42

[RustyPile]

Originally Posted by steeeeeve

..............<snip>I'm pretty sure I have a 4.11 rear end. But it seems a little bit sloppy. (jacked up)I can spin the wheel a bit before the drive shaft starts spinning. It seems too much but I really don't have a good reference.....<snip>....
thanks,
steeve

That's not a good way to check wear and back lash.. The back lash (slack) between the axle gears and the spider gears (both sides) is added in with the ring gear/pinion back lash.. The proper way is to remove the differential cover and lock down the drive shaft to prevent it's rotating.. Set up a dial indicator and "read" the ring gear movement..