73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: jamiebarnesjr3 on November 14, 2009, 06:22:39 am
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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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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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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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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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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.
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Event what trans do you have?
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700R4. I thought that was the trans in question.
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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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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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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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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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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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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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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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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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3.08 w/ 35's? wow. Do you have an indentation in the floorboard so the accelerator goes down further? You must have strong right foot muscles to hold that pedal down all the time to get that truck going. AND you have an OD trans. You'd use a lot of gas even on the interstate doing 75 because you'd always have to keep your accelerator pushed down! You need to take advantage of the correct rpms for your engine, and running it at 1100 rpms no matter the speed (i'm guessing) simply isn't using your engine efficiently. Hence, the reason for your question, which is a good one.
I have a 3.08 in my 383 w/ stock tire size. I wish I had at least 3.73. i concur, as if that means anything, with the rest of these guys. With 35's I'd be running at least a 4.10 to 4.56. That'll make it easier for your engine to run normally for city type traffic so you won't have to mash the gas all the time.
Your torque converter must get hot in your tranny with that set up. I hope you have an external tranny cooler.