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Author Topic: rearend qs  (Read 8450 times)

Offline jamiebarnesjr3

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rearend qs
« on: November 14, 2009, 06:22:39 am »
i was just wonderin if i could get some rear advice my truck is a 1984 k10 swb 4x4 with a 1999 vortec 350 mated to a 700r4 granny tranny (gm goodwrench) i have no lift but i am running 35/12.50/15 tires. i was wondering what gear ratio everyone would recomend im curious to see the differrent opinions i get im currently running the 3.08 rears also will a 10 bolt car rear out of a 79 z28 will the gears swap into my rears
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Offline Blazin

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Re: rearend qs
« Reply #1 on: November 14, 2009, 06:32:16 am »
The car gears won't fit in a truck carrier. As far as gears 3:73s or lower should work with your tires. Kinda depends on what you use it for. A daily driver that see a little off road here, and there 3:73s would be great. If you wheel it allot you might want 4:10s.
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Offline VileZambonie

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Re: rearend qs
« Reply #2 on: November 14, 2009, 07:41:13 am »
What's a 700R4 granny tranny? The granny tranny is a manual trans with really low 1st gear.... You have 35"s with no lift? So you must have cut away sheetmetal. 3.73:1 would be my choice
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Offline HAULIN IT

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Re: rearend qs
« Reply #3 on: November 14, 2009, 08:24:25 am »
Jamie & Blazin, If the truck has the original rears...(10 bolts) the gears, carriers, bearings, ect. will interchange front & rear...It's all the same carrier from 2.73 up through 4.56's or so. As in, you can take the posi unit out of the back of the Camaro & knock off your 3.08 ring & put it on either the front or the rear, find a 4.11 in a truck front & put the gears in the Camaro on it's original posi unit. Now 12 bolts, there are car & truck/van, also the newer (late 80's-up) the 10 bolts have different bearing ID-OD's car & truck/van, but can be made to work with some parts digging & a machinist help. I also agree with the 3.73's. Lorne     
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Offline eventhorizon66

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Re: rearend qs
« Reply #4 on: November 14, 2009, 11:06:59 am »
3.73 ?  Really?  I run 3.73 gears on my 4000 lb C10 with 29" tires and sometimes wish I had more gear.  I would think 4.10 minimum or even 4.56 with 35" tires.

At 65 mph:  3.08 = 1345 rpm (whoa, can you even use 4th gear at this speed?)
                 3.73 = 1630 rpm (bogged down)
                 4.10 = 1791 rpm (little better)
                 4.56 = 1992 rpm (perfect)

The above is just my humble opinion.  The guys that have advised you so far have much more experience than I do, but if it were me, I'd likely go with 4.56 gears.
« Last Edit: November 14, 2009, 11:08:50 am by eventhorizon66 »
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Offline VileZambonie

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Re: rearend qs
« Reply #5 on: November 14, 2009, 12:53:32 pm »
Event what trans do you have?
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Offline eventhorizon66

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Re: rearend qs
« Reply #6 on: November 14, 2009, 01:52:19 pm »
700R4.  I thought that was the trans in question.
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Offline VileZambonie

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Re: rearend qs
« Reply #7 on: November 14, 2009, 02:04:23 pm »
No, 3.73:1 is perfectly fine. I wouldn't go more than a 4.10:1 unless you're going bigger down the road...
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Offline jamiebarnesjr3

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Re: rearend qs
« Reply #8 on: November 14, 2009, 02:45:40 pm »
Quote from: VileZambonie on November 14, 2009, 07:41:13 am
What's a 700R4 granny tranny? The granny tranny is a manual trans with really low 1st gear.... You have 35"s with no lift? So you must have cut away sheetmetal. 3.73:1 would be my choice

yes ive heard of the 4 spped granny low but where im from we call the 700r4 the granny tranny because of its prone to leave ya on the side of a trail. mines not to bad but i paid 1800 for mine from gm and it has a few extra goodies sorry for the confusion. and i am running 35s with no lift at all not even body. ive been told it may be a big 10 is why its sits so high or it may be the fact that it is a canadian made truck not really sure but ive asked every mechanic thats worked on it an they all say there is no lift i will post some pics later.

as far as gears go i drive this truck everyday it is my work truck i run a homeimprovement bussines. i would actually like to get a lil better mileage im running a vortec 350 built with a edelbrock performer rpm air gap intake, accell hei distributer headers,straight duels with summit glass packs, edelbrock 600 600 cfm 4 bbl. and a performer rpm cam and 1.6 aluminum rollers estimated around 350 hp maybe more but thats a safe number. im runn about 9 mpg any ideas
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Offline zieg85

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Re: rearend qs
« Reply #9 on: November 14, 2009, 03:10:15 pm »
If everything is tuned and running good the easiest thing to try would be go to stock height tires temporarily and see if your mileage improves.  That is a lot of tire for 35's for sure.
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Offline Blazin

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Re: rearend qs
« Reply #10 on: November 15, 2009, 12:01:06 am »
Years back I tried to swap the carrier out of my 74 Malibu in to a 85 10 bolt in a C 10. It was smaller.
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Offline joesgarage71

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Re: rearend qs
« Reply #11 on: November 15, 2009, 08:54:08 am »
 35's I'd have at least 4.10 gears, I have 4.56's with 36's in my mudd truck, runs good
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Offline VileZambonie

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Re: rearend qs
« Reply #12 on: November 15, 2009, 09:06:58 am »
I've never heard anyone refer to the 700R4 as a granny tranny.... As far as swapping R&P and carriers if you're referring to the 8.5 GM 10 bolt I believe the only differences were axles and spline counts.

There's no way you have no lift and fit 35"s
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Offline eventhorizon66

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Re: rearend qs
« Reply #13 on: November 15, 2009, 11:07:31 am »
Quote from: VileZambonie on November 15, 2009, 09:06:58 am
There's no way you have no lift and fit 35"s

This is beginning to really bother Vile.  We're gonna need to see some pics. :P
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Offline Irish_Alley

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Re: rearend qs
« Reply #14 on: November 16, 2009, 12:09:47 am »
Quote from: VileZambonie on November 15, 2009, 09:06:58 am
There's no way you have no lift and fit 35"s
unless he has no fenders hint the need for the flares  ;)
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