What do you think of this setup? sb400/700r4/.308 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Hazieview · 01-04-2009, 01:29 AM

I now have a sb400/350th/.308 I am thinking abou replacing the transmisson with a 700r4 because my th350 is giving me problems. I put it in gear and the truck doesn't move. Sometimes it takes it a wall to actually go in gear so I think it has probably been hammered too much. I figured that with the sb400 I'll have plenty of torque like always but I have a quiter and more effiecient ride with the 700r4 because I'll be running lower rpms when cruising down the highway. Right now I can smoke that one rear tire no problem but it's getting to be less fun these days. I'd rather just make an everyday driver that still sounds good and will get down when I need/want it too. Figured it would be less strain on my engine as well. However I just hope I dont destroy the trani or rearend with the kind of torque that sb400 can make. I'm planning on beefing it up a little but right now it just has a performer intake and a small rv cam. Sooooo.....

What do you guys think?

Blazer Eagle · 01-04-2009, 01:31 AM

well the 700r4 actually has a lower first gear so you could smoke your tires a little better, however it does have the 4th over drive gear which does run you in lower rpms

Hazieview · 01-04-2009, 01:34 AM

Sounds like what I'm looking for... Smoke 'em when you feel the need and still get down the highway a little more comfortable and affordable than the 350th..... ?

krue · 01-04-2009, 01:40 AM

My truck with the stock 350 a 2004-r and 3.07 gears seems like it is a dog on the hiway in o/d. I'm looking for a 3.73 rear gear to get the hwy rpm back up to about 2k which is where my 350 likes to hang out.

Hazieview · 01-04-2009, 03:05 AM

So would the sb400/700r4/.308 be a dog too? I figured as long as you had a kick down you shouldn't have any problems....?

Pyrotechnic · 01-04-2009, 03:32 AM

Depends on tire size. With a 28" or larger tire and an older flat tappet cam motor, forget it. You need at least 3.42's. It's going to want to shift out of OD constantly. A 400 MIGHT get away with it, but it's still a less than ideal setup. You might even get worse gas mileage because the engine isn't in it's sweet spot.

With a newer roller cam, fuel injected motor with modern heads and high compression, it can work, but that's a whole different ball game.

krue · 01-04-2009, 03:35 AM

My 92 with TBI will run a lot lower RPM at hiway speeds without much trouble, but my 70 is a dog. It actually worked better with the th350 in it but I wanted the 4 speed to get a lower first gear more than having the o/d. You're probably better off with a stout th350 and the rear you have.

66truckin · 01-04-2009, 03:56 AM

as was previously said you need at least a 3.42 gear to run that 700-r4. You would have no problem doing 150mph with that 3.08 though

fast75 · 01-04-2009, 05:04 AM

some things to consider before doing this swap. the cost of rebuilding a 700r4 is almost double that of rebuilding a 350 or 400. the 308 gearing you speak of isn't going to cut it with a 700, it'll fall on its face. i have two buddies who tried 700's and both have since took them out. if you decide on the 700, go with at least 342 gearing, 373 would be better and still good on the hwy. just my two cents............divide the number of teeth on the ring gear by the number of teeth on the pinion to figure your gear ratio...............

Hazieview · 01-04-2009, 07:35 AM

I use to have a .373 posi rearend. The truck would leave HARD!!! Now it doesn't leave as hard but will still smoke the hell out of that one tire. However I top out at like 110mph.....

So what you all are saying i'll be better off keeping the th350 and rebuilding it?

b454rat · 01-04-2009, 09:36 AM

I had a 90 GMC that I built years ago. Had a real nice 406 in it. Was originally 350/700/3.08s. It wasn't tearable with the 350, but after I put the 400 in it, thing was a monster. It never down shifted on the highway, converter never unlocked either. I live in NYS, and at the time was in the military and stationed in DC. On I81, there are some hills, and never had a problem.

My current truck has the same combo, up to 3rd it's not bad, but was in OD it is a dog. A 454 will cure that....

I was gonna put my 400 into it, but have the 454, and get a cummins, so dont' have a use for a small motor anymore....

CAMAROSS · 01-04-2009, 11:42 AM

Im running a 406 small block with a 700R in my truck. I also have the TBI still fueling it, RV cam, factory heads, etc. and it gets on down the road and is smooth in overdrive. Dont know what gears I have in the rear though. I say go for it.

Hazieview · 01-04-2009, 05:45 PM

So I'm back to lost. Will the sb400/700r/.308 be a dog on the highway too? I mean if you wanted to pass someone couldn't you just hit the gas so it down shift and go around them? As long as the trani didn't keep popping out of overdrive when you cruising about 70 I dont see a problem... Come on guys dumb it down a little more for me...

LONGHAIR · 01-04-2009, 06:03 PM

I am another one to say that you need at leat a 3.42 gear and 3.73 is probably better. You will probably have shifting/searching for a gear issues, depending upon your actual highway speed. The main misconception though is that you will gain fuel mileage by slowing the engine down. It is not neceaasrily so. If you get too low, you get out of the optimal RPM range. That is not any better for fuel mileage. If you are geared too high, the transmission has to downshift, then you are revved way up and defeated the whole thing.

ton*loc · 01-04-2009, 06:30 PM

Quote:

Originally Posted by Hazieview

So I'm back to lost. Will the sb400/700r/.308 be a dog on the highway too? I mean if you wanted to pass someone couldn't you just hit the gas so it down shift and go around them? As long as the trani didn't keep popping out of overdrive when you cruising about 70 I dont see a problem... Come on guys dumb it down a little more for me...

ok with the 3.08 gears driving down the highway your truck will be at 1300-1400 rpms and your cruzing along and want to pass someone you push on the gas a little and it seams like your not getting any where because your motor makes no power at 1300 rpms. so you push a little more and a little more then finally it down shifts up 2300rpm. you pass the guy and then 50 yards down the road you have to pass some one again so the same thing happens you push on the gas more and more then finally down shifts back up to 2300 so on your little road trip you had your tranny up shift and down swift 25 times.

with the 3.73 your car will always be at 2000-2100 rpms on the highway so when you come up behind grandma and you need to pass her all you are going to need to do is just a little press down on the pedal and around you go because your motor is already in its sweet spot.

its just going to be a dog and annoying to have that combo and your just going to want to change it later when you get fed up with it so you might as well do it now.

comprenda

northern 85 · 01-04-2009, 07:31 PM

Bump up the hp and tq you can run what ever gear you want ,imop if your motor wont pull your gear you need more hp!

slugish · 01-04-2009, 09:50 PM

My 2 cents ; REBUILD YOUR 350 TRANS- KEEP YOUR 3.08 GEARS & CRUISE ON . USE ANYTHING XTRA FOR OTHER MODS. WITH A 3SPEED TRANS --3.08 >3.43 GEARING . FOR A 700 3.42- 3.73 GEARING , PRETTY MUCH WHAT EVERYONE ELSE HAS SAID & I AGREE 100%

chevymotocross · 01-04-2009, 10:22 PM

I have an 87 with the 305 fuel injected engine, 700r4, and 3.08 gears. I absolutely hate the 3.08 gears. I find myself not even using OD since it constantly shifts in and out.

Unless my truck is not loaded with anything in the bed, on highway with no inclines, doing atleast 65, and with no one to pass, I can cruise along in OD.

First gear is awesome with the 700r4. As soon as it shifts into 2nd, it falls flat on its face due to the 3.08 gears and probably my weak 305.

ton*loc · 01-05-2009, 12:03 AM

Quote:

Originally Posted by northern 85

Bump up the hp and tq you can run what ever gear you want ,imop if your motor wont pull your gear you need more hp!

at 1300 ?

Tony@AirRideTech · 01-05-2009, 12:02 PM

If it were me..... I would bump up the gearing to either 342's or 373's. if that is a stock 700R4... I would also go ahead and go into it and replace the bands and clutches to aftermarket hD pieces. Those trannys are great pieces they just dont like alot of horsepower in stock trim.

b454rat · 01-05-2009, 12:24 PM

Even the 4wds are geared like this. Dang near every truck I see in yards has 3.42 gears with 245 or 265 tires. That is equivlant to 3.08s and 28/29" tall tires. If you build your motor up some, you will have plenty of power to maintain speed, probly won't even downshift.

IMO 3 speeds are useless inless it's a drag car, or stupid amounts of power are being made. There are times where I like or need to go faster than 70, and with a 3 speed the R's get up there quick. Not to mention the motor will last longer not turning high RPMs for long periods.

I live in NYS, there are alot of hills. Even in my truck, pulling a hill with weight in the back, it still doesn't downshift. It slows down, but doesn't downshift inless I need it to....

jchav62 · 01-05-2009, 12:38 PM

I agree with the others. With an overdrive trans, go with a 3.42 or a 3.73 gear. Even with a 400, in OD with a 3.08, seems that the RPM's would be way too low, and it'll constantly be shifting. In my '62 with a mild 327, I used to have 3.08's and a th350..it did fine on the highway. Now I have 3.73's with a GearVendor overdrive. Off the line it's a lot quicker now compared to the 3.08's, and on the highway with the OD on it does about the same as it did with 3.08's.

My Final answer:

th350 with 3.08's
700r4 with 3.42's or lower.

Hazieview · 01-05-2010, 08:53 PM

Well I'm waking up this thread again. I've decided to pep up my sb400. I'm going to put an air gap on it, new heads and turn it into a full roller. (I was going to spend the money on forged rods and pistons but decided to roll it instead)

So full roller sb400 350th trani and .308 rearend.

The 400 should be able to handle a little higher rpms so we'll see what happends.

I would love to have a sb400 bullet proof 700r4 and .373 posi. However that would cost thousands for the trani and rearend so we'll see what happens!!!

joe231 · 01-05-2010, 09:28 PM

The rear gearing is totally dependant on tire size. What tire size are you running?
gchemist is running 255/60/15's with a 355-700r4 combo and 3.08 gears. he is happy with it.

slugish · 01-05-2010, 09:55 PM

Quote:

Originally Posted by Hazieview

Well I'm waking up this thread again. I've decided to pep up my sb400. I'm going to put an air gap on it, new heads and turn it into a full roller. (I was going to spend the money on forged rods and pistons but decided to roll it instead)

So full roller sb400 350th trani and .308 rearend.

The 400 should be able to handle a little higher rpms so we'll see what happends.

I would love to have a sb400 bullet proof 700r4 and .373 posi. However that would cost thousands for the trani and rearend so we'll see what happens!!!

Iagree with you 100 % .Ive had a 3.73 -a 3.08 & a 3.42 in my 408 / 350 .

currently a 3.42 ,but on the highway cruisin still too many rpms > usually Ijust slow down & run only 60-65 mph at approx. 2500 rpms .

yea, just beef up that ole 400 & stick with your 3.08 > best of both worlds . If you do this let me know what you think by a pm . Good Luck

01-04-2009, 01:29 AM	#1
Hazieview Building Dreams out of Dimes! Join Date: May 2005 Location: Bonham, Tx Posts: 892	What do you think of this setup? sb400/700r4/.308 I now have a sb400/350th/.308 I am thinking abou replacing the transmisson with a 700r4 because my th350 is giving me problems. I put it in gear and the truck doesn't move. Sometimes it takes it a wall to actually go in gear so I think it has probably been hammered too much. I figured that with the sb400 I'll have plenty of torque like always but I have a quiter and more effiecient ride with the 700r4 because I'll be running lower rpms when cruising down the highway. Right now I can smoke that one rear tire no problem but it's getting to be less fun these days. I'd rather just make an everyday driver that still sounds good and will get down when I need/want it too. Figured it would be less strain on my engine as well. However I just hope I dont destroy the trani or rearend with the kind of torque that sb400 can make. I'm planning on beefing it up a little but right now it just has a performer intake and a small rv cam. Sooooo..... What do you guys think? Last edited by Hazieview; 01-04-2009 at 01:31 AM.

01-04-2009, 01:31 AM	#2
Blazer Eagle Registered User Join Date: Oct 2008 Location: PLacerville, CA Posts: 195	Re: What do you think of this setup? sb400/700r4/.308 well the 700r4 actually has a lower first gear so you could smoke your tires a little better, however it does have the 4th over drive gear which does run you in lower rpms

01-04-2009, 01:34 AM	#3
Hazieview Building Dreams out of Dimes! Join Date: May 2005 Location: Bonham, Tx Posts: 892	Re: What do you think of this setup? sb400/700r4/.308 Sounds like what I'm looking for... Smoke 'em when you feel the need and still get down the highway a little more comfortable and affordable than the 350th..... ?

01-04-2009, 01:40 AM	#4
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,450	Re: What do you think of this setup? sb400/700r4/.308 My truck with the stock 350 a 2004-r and 3.07 gears seems like it is a dog on the hiway in o/d. I'm looking for a 3.73 rear gear to get the hwy rpm back up to about 2k which is where my 350 likes to hang out. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

01-04-2009, 03:05 AM	#5
Hazieview Building Dreams out of Dimes! Join Date: May 2005 Location: Bonham, Tx Posts: 892	Re: What do you think of this setup? sb400/700r4/.308 So would the sb400/700r4/.308 be a dog too? I figured as long as you had a kick down you shouldn't have any problems....?

01-04-2009, 03:32 AM	#6
Pyrotechnic Registered User Join Date: Feb 2007 Location: Austin, TX Posts: 3,930	Re: What do you think of this setup? sb400/700r4/.308 Depends on tire size. With a 28" or larger tire and an older flat tappet cam motor, forget it. You need at least 3.42's. It's going to want to shift out of OD constantly. A 400 MIGHT get away with it, but it's still a less than ideal setup. You might even get worse gas mileage because the engine isn't in it's sweet spot. With a newer roller cam, fuel injected motor with modern heads and high compression, it can work, but that's a whole different ball game. __________________ 1977 GMC Sierra Grande Last edited by Pyrotechnic; 01-04-2009 at 03:35 AM.

01-04-2009, 03:35 AM	#7
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,450	Re: What do you think of this setup? sb400/700r4/.308 My 92 with TBI will run a lot lower RPM at hiway speeds without much trouble, but my 70 is a dog. It actually worked better with the th350 in it but I wanted the 4 speed to get a lower first gear more than having the o/d. You're probably better off with a stout th350 and the rear you have. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

01-04-2009, 03:56 AM	#8
66truckin Registered User Join Date: Jan 2009 Location: Springfield, IL Posts: 185	Re: What do you think of this setup? sb400/700r4/.308 as was previously said you need at least a 3.42 gear to run that 700-r4. You would have no problem doing 150mph with that 3.08 though

01-04-2009, 05:04 AM	#9
fast75 Go Hard or Go Home! Join Date: Dec 2008 Location: quitman, tx Posts: 261	Re: What do you think of this setup? sb400/700r4/.308 some things to consider before doing this swap. the cost of rebuilding a 700r4 is almost double that of rebuilding a 350 or 400. the 308 gearing you speak of isn't going to cut it with a 700, it'll fall on its face. i have two buddies who tried 700's and both have since took them out. if you decide on the 700, go with at least 342 gearing, 373 would be better and still good on the hwy. just my two cents............divide the number of teeth on the ring gear by the number of teeth on the pinion to figure your gear ratio............... __________________ 75 short wide 350, some mods, scare the piss outta ya quick. 2008 Dodge crew cab. YEAH, it's got a hemi, your ass is going to jail quick. Some day's, it's just not worth chewing through the restraints................................

01-04-2009, 07:35 AM	#10
Hazieview Building Dreams out of Dimes! Join Date: May 2005 Location: Bonham, Tx Posts: 892	Re: What do you think of this setup? sb400/700r4/.308 I use to have a .373 posi rearend. The truck would leave HARD!!! Now it doesn't leave as hard but will still smoke the hell out of that one tire. However I top out at like 110mph..... So what you all are saying i'll be better off keeping the th350 and rebuilding it?

01-04-2009, 09:36 AM	#11
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,454	Re: What do you think of this setup? sb400/700r4/.308 I had a 90 GMC that I built years ago. Had a real nice 406 in it. Was originally 350/700/3.08s. It wasn't tearable with the 350, but after I put the 400 in it, thing was a monster. It never down shifted on the highway, converter never unlocked either. I live in NYS, and at the time was in the military and stationed in DC. On I81, there are some hills, and never had a problem. My current truck has the same combo, up to 3rd it's not bad, but was in OD it is a dog. A 454 will cure that.... I was gonna put my 400 into it, but have the 454, and get a cummins, so dont' have a use for a small motor anymore.... __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 6” lift 1999 GMC Yukon 350/4L60 4" SAS

01-04-2009, 11:42 AM	#12
CAMAROSS Registered User Join Date: Jan 2007 Location: Sulphur Springs, Tx Posts: 100	Re: What do you think of this setup? sb400/700r4/.308 Im running a 406 small block with a 700R in my truck. I also have the TBI still fueling it, RV cam, factory heads, etc. and it gets on down the road and is smooth in overdrive. Dont know what gears I have in the rear though. I say go for it.

01-04-2009, 05:45 PM	#13
Hazieview Building Dreams out of Dimes! Join Date: May 2005 Location: Bonham, Tx Posts: 892	Re: What do you think of this setup? sb400/700r4/.308 So I'm back to lost. Will the sb400/700r/.308 be a dog on the highway too? I mean if you wanted to pass someone couldn't you just hit the gas so it down shift and go around them? As long as the trani didn't keep popping out of overdrive when you cruising about 70 I dont see a problem... Come on guys dumb it down a little more for me... Last edited by Hazieview; 01-04-2009 at 05:45 PM.

01-04-2009, 07:31 PM	#16
northern 85 Registered User Join Date: Mar 2005 Location: Fairfield Maine Posts: 1,759	Re: What do you think of this setup? sb400/700r4/.308 Bump up the hp and tq you can run what ever gear you want ,imop if your motor wont pull your gear you need more hp!

01-04-2009, 09:50 PM	#17
slugish Slugish Join Date: Jan 2005 Location: Earlysville, Va. Posts: 1,024	Re: What do you think of this setup? sb400/700r4/.308 My 2 cents ; REBUILD YOUR 350 TRANS- KEEP YOUR 3.08 GEARS & CRUISE ON . USE ANYTHING XTRA FOR OTHER MODS. WITH A 3SPEED TRANS --3.08 >3.43 GEARING . FOR A 700 3.42- 3.73 GEARING , PRETTY MUCH WHAT EVERYONE ELSE HAS SAID & I AGREE 100%



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01-04-2009, 10:22 PM	#18
chevymotocross Registered User Join Date: May 2007 Location: East Haven, CT Posts: 882	Re: What do you think of this setup? sb400/700r4/.308 I have an 87 with the 305 fuel injected engine, 700r4, and 3.08 gears. I absolutely hate the 3.08 gears. I find myself not even using OD since it constantly shifts in and out. Unless my truck is not loaded with anything in the bed, on highway with no inclines, doing atleast 65, and with no one to pass, I can cruise along in OD. First gear is awesome with the 700r4. As soon as it shifts into 2nd, it falls flat on its face due to the 3.08 gears and probably my weak 305. __________________ 87 Chevy 2wd SWB: 305/700r4 Dual Exhaust, K&N Filter, Injector Pod Spacer, TBI Spacer, Belltech Front Sway Bar, Corvette Servo, Western Chassis 4/6 and c-notch

01-05-2009, 12:02 PM	#20
Tony@AirRideTech Junior Member Join Date: Feb 2005 Location: Huntingburg IN Posts: 620	Re: What do you think of this setup? sb400/700r4/.308 If it were me..... I would bump up the gearing to either 342's or 373's. if that is a stock 700R4... I would also go ahead and go into it and replace the bands and clutches to aftermarket hD pieces. Those trannys are great pieces they just dont like alot of horsepower in stock trim.

01-05-2009, 12:24 PM	#21
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,454	Re: What do you think of this setup? sb400/700r4/.308 Even the 4wds are geared like this. Dang near every truck I see in yards has 3.42 gears with 245 or 265 tires. That is equivlant to 3.08s and 28/29" tall tires. If you build your motor up some, you will have plenty of power to maintain speed, probly won't even downshift. IMO 3 speeds are useless inless it's a drag car, or stupid amounts of power are being made. There are times where I like or need to go faster than 70, and with a 3 speed the R's get up there quick. Not to mention the motor will last longer not turning high RPMs for long periods. I live in NYS, there are alot of hills. Even in my truck, pulling a hill with weight in the back, it still doesn't downshift. It slows down, but doesn't downshift inless I need it to.... __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 6” lift 1999 GMC Yukon 350/4L60 4" SAS

01-05-2009, 12:38 PM	#22
jchav62 1962 C-10 Join Date: Apr 2005 Location: Las Vegas, New Mexico Posts: 4,978	Re: What do you think of this setup? sb400/700r4/.308 I agree with the others. With an overdrive trans, go with a 3.42 or a 3.73 gear. Even with a 400, in OD with a 3.08, seems that the RPM's would be way too low, and it'll constantly be shifting. In my '62 with a mild 327, I used to have 3.08's and a th350..it did fine on the highway. Now I have 3.73's with a GearVendor overdrive. Off the line it's a lot quicker now compared to the 3.08's, and on the highway with the OD on it does about the same as it did with 3.08's. My Final answer: th350 with 3.08's 700r4 with 3.42's or lower. __________________ Joseph Chavez "See the USA in a Chevrolet!!" ......................_____ .........________//__{\_____ ,,,,,,,/__(O)___//___/__(O)_/ 1962 C10 Shortbed Fleetside 327/th350 GV overdrive 1974 C10 Longbed Fleetside 350/th350 "The Trash Truck" 1999 Chevy 2500 OBS, Longbed 5.7/4L80E 4x4 2015 GMC Sierra SLE 1500 4x4

01-05-2010, 08:53 PM	#23
Hazieview Building Dreams out of Dimes! Join Date: May 2005 Location: Bonham, Tx Posts: 892	Re: What do you think of this setup? sb400/700r4/.308 Well I'm waking up this thread again. I've decided to pep up my sb400. I'm going to put an air gap on it, new heads and turn it into a full roller. (I was going to spend the money on forged rods and pistons but decided to roll it instead) So full roller sb400 350th trani and .308 rearend. The 400 should be able to handle a little higher rpms so we'll see what happends. I would love to have a sb400 bullet proof 700r4 and .373 posi. However that would cost thousands for the trani and rearend so we'll see what happens!!!

01-05-2010, 09:28 PM	#24
joe231 Registered User Join Date: Dec 2007 Location: Palmer, Alaska Posts: 13,821	Re: What do you think of this setup? sb400/700r4/.308 The rear gearing is totally dependant on tire size. What tire size are you running? gchemist is running 255/60/15's with a 355-700r4 combo and 3.08 gears. he is happy with it. __________________ *CHEVY ONLY* Last edited by joe231; 01-05-2010 at 09:30 PM.

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