90 k1500 rear end....

smokensteve · 02-05-2007, 01:04 AM

How does one find out what rear end gearing you have ...I have a 90 k1500 silverado Z71 with a 5.7 what would be standard rear end ..does anyone know????....and what would be a good change to give me a little more street speed...I would like a little more umphfff on the street but don't want to loose all 4x4 torgue....still want good highway driving too

mudseeker · 02-05-2007, 03:39 AM

if you want more umphf i would go for a cam swap. my 2 cents.

smokensteve · 02-05-2007, 04:08 AM

Quote:

Originally Posted by mudseeker

if you want more umphf i would go for a cam swap. my 2 cents.

yeah part of my plan ......but I'm was just wondering what gearing anyone thinks would be in my truck...and what might make me quicker in town, without losing highway driving ???

westboundchevy · 02-05-2007, 09:04 AM

have you done a shifter-improver kit?
they're pretty inexpensive and you may find that it's all you want.
lowering the gearing in the rear-end would definitely eat into your ability drive effeciently at highway speeds.
what tranny do you have?

75K30 · 02-05-2007, 10:55 AM

The easy way to do this is to lift one rear tire, and turn it one revolution, and count the number of times the driveshaft rotates. If you have a traction device, (posi) you will have to lift both tires. The gov. loc will work with just one tire, you will never spin it fast enough to engage it.
You should expect about 3 and a half revolutions, to about 3 and three quarter revolutions. In order to really answer you question, we will also need to know what size tire you are running now. If you have increased the tire size, you have killed much of the overall ratio.
Changing the gears will give you the best acceleration for money invested. Some guys even install a lower first gear in the trans. for better stop light acceleration.

bradrhale · 02-05-2007, 11:37 AM

thats alot of gears to change. if you go changing things in the back, being a k1500, you will have to change your front end also to compensate. what about a good tranny custom built to gears that is desired, although that that would probably costs just as much as both gear changes put together.

smokensteve · 02-05-2007, 12:18 PM

Quote:

Originally Posted by bradrhale

thats alot of gears to change. if you go changing things in the back, being a k1500, you will have to change your front end also to compensate. what about a good tranny custom built to gears that is desired, although that that would probably costs just as much as both gear changes put together.

I will be doing some tranny work probably in a month or so...I think second gear is screwy..so while tranny is down, what, if any, are some kits I can buy.. I will be changing all bearings and sycros...while i do this is there something else I can buy ...do I have to buy actual gears or do they come with bearing kit...the tires I have on it right now...they were on it when I bought it, are 265 75 r16's...

75K30 · 02-05-2007, 12:54 PM

The disadvantage to making the gear change in the trans, is that it is only beneficial for one gear,(unless you change them all, which would make no sense). The advantage to changing the differential gears, is that you recieve the performance advantages through all of the gears. Given the stock tire size approx 32" tall, you will experience about a 200 rpm difference in engine rpm by going to a 4.10:1 (if you currently have 3.73:1), or a 400 rpm difference if you have 3.55:1 gears. This would give you the best bang for your buck, for every driving style. You will notice a considerable improvement in truck performance, when you want it. With a better mechanical advantage, you may even see better around town mileage, with little loss on the highway. Yes, you will have to change both differentials, but it is worth it.

smokensteve · 02-05-2007, 02:44 PM

thanks for all the info...after considering everything ..I think I just may leave stock for now....

nate3436 · 02-05-2007, 07:05 PM

You most likely have a 3:42 ratio. That was pretty common in 88-93. I had a 91 and changed out the gears and it really isn't that bad. It takes about a day for both. I would go with 4:11 if you have the stock 700r4. I had a th350 and went with 3:73 cause the no overdrive. While you have the rear end apart you may want to look into a good differential. Auburn and Detroit have real good medium duty applications that don't cost a fortune either.

02-05-2007, 01:04 AM	#1
smokensteve Senior Member Join Date: Jan 2007 Location: North Vancouver BC Posts: 86	90 k1500 rear end.... How does one find out what rear end gearing you have ...I have a 90 k1500 silverado Z71 with a 5.7 what would be standard rear end ..does anyone know????....and what would be a good change to give me a little more street speed...I would like a little more umphfff on the street but don't want to loose all 4x4 torgue....still want good highway driving too

02-05-2007, 03:39 AM	#2
mudseeker mod-o-tator Join Date: Feb 2006 Location: michigan Posts: 4,524	if you want more umphf i would go for a cam swap. my 2 cents. __________________ member map add yourself alldatadiy why is it, when i push one for english, i still can't understand the person on the other end?

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02-05-2007, 09:04 AM	#4
westboundchevy Full Member Join Date: Jan 2007 Location: Fayetteville, NC Posts: 40	have you done a shifter-improver kit? they're pretty inexpensive and you may find that it's all you want. lowering the gearing in the rear-end would definitely eat into your ability drive effeciently at highway speeds. what tranny do you have?

02-05-2007, 10:55 AM	#5
75K30 Senior Member Join Date: Jul 2006 Posts: 2,636	The easy way to do this is to lift one rear tire, and turn it one revolution, and count the number of times the driveshaft rotates. If you have a traction device, (posi) you will have to lift both tires. The gov. loc will work with just one tire, you will never spin it fast enough to engage it. You should expect about 3 and a half revolutions, to about 3 and three quarter revolutions. In order to really answer you question, we will also need to know what size tire you are running now. If you have increased the tire size, you have killed much of the overall ratio. Changing the gears will give you the best acceleration for money invested. Some guys even install a lower first gear in the trans. for better stop light acceleration.

02-05-2007, 11:37 AM	#6
bradrhale Moderator Join Date: Apr 2006 Location: Texas Posts: 3,605	thats alot of gears to change. if you go changing things in the back, being a k1500, you will have to change your front end also to compensate. what about a good tranny custom built to gears that is desired, although that that would probably costs just as much as both gear changes put together.

02-05-2007, 12:54 PM	#8
75K30 Senior Member Join Date: Jul 2006 Posts: 2,636	The disadvantage to making the gear change in the trans, is that it is only beneficial for one gear,(unless you change them all, which would make no sense). The advantage to changing the differential gears, is that you recieve the performance advantages through all of the gears. Given the stock tire size approx 32" tall, you will experience about a 200 rpm difference in engine rpm by going to a 4.10:1 (if you currently have 3.73:1), or a 400 rpm difference if you have 3.55:1 gears. This would give you the best bang for your buck, for every driving style. You will notice a considerable improvement in truck performance, when you want it. With a better mechanical advantage, you may even see better around town mileage, with little loss on the highway. Yes, you will have to change both differentials, but it is worth it.

02-05-2007, 02:44 PM	#9
smokensteve Senior Member Join Date: Jan 2007 Location: North Vancouver BC Posts: 86	thanks for all the info...after considering everything ..I think I just may leave stock for now....

02-05-2007, 07:05 PM	#10
nate3436 Full Member Join Date: Jan 2006 Location: Southeast Iowa Posts: 45	You most likely have a 3:42 ratio. That was pretty common in 88-93. I had a 91 and changed out the gears and it really isn't that bad. It takes about a day for both. I would go with 4:11 if you have the stock 700r4. I had a th350 and went with 3:73 cause the no overdrive. While you have the rear end apart you may want to look into a good differential. Auburn and Detroit have real good medium duty applications that don't cost a fortune either.