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Author Topic: ok gears are in  (Read 2026 times)

Offline Buddy

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ok gears are in
« on: June 08, 2011, 02:30:52 pm »
Ok, first off let me say i have a 85 , 305 4x4 which had 308 in it for gears. I am running 35" tires with a 700r tranny. I found this truck extremly lazy just never had any power and gas mileage was the worst I have ever seen on any truck. The motor is strong so I knew it wasnt that. The people that I talked said is was my gears and needed to upgrade. Last night I came across a guy that had a set of 373. So I swamped them out, was a little nervous at first but after I got into it wasn't that bad.. (thanks youtube) anyways after I installed them I took it for a drive and I did notice a little improvement in power. The first thing I noticed is it seems to shift way better now. However the power gain was not what I was hoping for. I guess I will have to live with that. My next question is now my speedo is WAY out of whack, is there a way to adjust this. I would say it is out by at least 40 kmh.  any input on the gear swap and the power and the speedo is great...thanks in advance.  also forgot to ask do you think my mileage will improve?
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Offline Grim 82

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Re: ok gears are in
« Reply #1 on: June 08, 2011, 02:41:07 pm »
Theoretically your mileage should improve. To get your speedometer right you will need to replace the plastic speedo gears. I'm guessing you have a np208 t-case since it's an 85 with a 700r4. The drive gear is a sleeve that slides over the t-case output shaft and the driven gear is in the speedo housing where the cable hooks up to the tail housing. It's an easy swap, just remove the driveshaft, speedo cable and housing, and the tailhousing for the t-case. Figuring out exactly which gears you need to put back in it to make it read accurately is dependant on your tire height, trans ratios and rear end gear.
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Offline Buddy

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Re: ok gears are in
« Reply #2 on: June 08, 2011, 02:43:49 pm »
sorry i should have said i have a 305 transfer case.. and as far as everything else you said.....wow i am lost.
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Offline Grim 82

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Re: ok gears are in
« Reply #3 on: June 08, 2011, 03:29:48 pm »
205 case? I think it's the same principal, but I'm not too familiar with the 205. You can also buy a ratio adapter from the looks of it.
Here are some pics of what I am talking about.
http://www.transmissioncenter.net/speedometer_calibration_______va.htm

edit: (the transfer case gears, not the trans mounted speedometer gears)
« Last Edit: June 08, 2011, 03:33:58 pm by Grim 82 »
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Give a man a gun, and he might rob a bank. Give a man a bank, and he might rob the world.
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