Drivetrain durability - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Brad_Olson · 05-27-2005, 11:46 AM

If I decide to keep my '86 K10 there's a reasonable chance that the 305 might be replaced with a mildly-built 350 or 400; with 2.73 gears the powerband would be in the 500-4000 RPM range. Since it's a 4-speed I'd probably install a new clutch at that time but will the transmission and transfer case be OK with a definite torque & HP increase over stock? Thanks!

Brad

**Captkaos** · 05-27-2005, 12:32 PM

If you are talking about the SM465, a 350 isn't going to break it. Even with a torque monster 454 infront of it breakage would be slim. You will break an axle or u-joint WAY before the Tranny is stressed.

plumbcut · 05-27-2005, 08:44 PM

I agree with Chris... you probably have a np208 case? Should be fine. Let er rip!

*1FaastC10* · 05-27-2005, 10:18 PM

for a 4x4, i would ditch the 2.73s. 3.42 and a set of 32-33" tires (which should fit at stock height would make it a much more drivable truck. the lower gears will help around town, and combined with the larger (than stock) tires, will only hurt you slightly if at all on the highway with a stock engine. since you're planning on beefing up the engine anyways, build for that powerband and you should be golden. you mentioned your powerband between 500-4000 rpms, NEVER run a small block under any kind of load at that RPM. lugging it down like that is just begging for failure. if you were just idling along, its a whole different ballgame.

the cheapest way to do the 3.42 swap would be to find someone who has upgraded their axles for strength reasons, and lower gears. 3.42 gears can commonly be found in Blazers and Suburbans of the late 80s and 90-91. probably the hot ticket would be to find a set of 82-87 light duty 3/4 tons. they'll bolt directly in, giving you bigger brakes, the gears you need, as well as the added strength of the 14 bolt Semi Floating rear axle.

i strongly recomend the rear axle upgrade anyways, i just broke a 10 bolt carrier, which in turn ate the ring and pinion. that was with a dead stock 170,000 mi truck, and bald 29" tires. and no, i wasnt abusing it.

Tom · 05-28-2005, 02:57 AM

I broke my sm465 in 20,000miles with a 383. Of course I seem to be the only person in the world to have done this so Id say your good to go.

05-27-2005, 11:46 AM	#1
Brad_Olson Active Member Join Date: Mar 2005 Location: Stoughton, WI Posts: 187	Drivetrain durability If I decide to keep my '86 K10 there's a reasonable chance that the 305 might be replaced with a mildly-built 350 or 400; with 2.73 gears the powerband would be in the 500-4000 RPM range. Since it's a 4-speed I'd probably install a new clutch at that time but will the transmission and transfer case be OK with a definite torque & HP increase over stock? Thanks! Brad

05-27-2005, 12:32 PM	#2
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	If you are talking about the SM465, a 350 isn't going to break it. Even with a torque monster 454 infront of it breakage would be slim. You will break an axle or u-joint WAY before the Tranny is stressed. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

05-28-2005, 02:57 AM	#5
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,748	I broke my sm465 in 20,000miles with a 383. Of course I seem to be the only person in the world to have done this so Id say your good to go. __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.

05-27-2005, 08:44 PM	#3
plumbcut california fill Join Date: Apr 2004 Location: Sunny So-Cal Posts: 694	I agree with Chris... you probably have a np208 case? Should be fine. Let er rip!

05-27-2005, 10:18 PM	#4
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,399	for a 4x4, i would ditch the 2.73s. 3.42 and a set of 32-33" tires (which should fit at stock height would make it a much more drivable truck. the lower gears will help around town, and combined with the larger (than stock) tires, will only hurt you slightly if at all on the highway with a stock engine. since you're planning on beefing up the engine anyways, build for that powerband and you should be golden. you mentioned your powerband between 500-4000 rpms, NEVER run a small block under any kind of load at that RPM. lugging it down like that is just begging for failure. if you were just idling along, its a whole different ballgame. the cheapest way to do the 3.42 swap would be to find someone who has upgraded their axles for strength reasons, and lower gears. 3.42 gears can commonly be found in Blazers and Suburbans of the late 80s and 90-91. probably the hot ticket would be to find a set of 82-87 light duty 3/4 tons. they'll bolt directly in, giving you bigger brakes, the gears you need, as well as the added strength of the 14 bolt Semi Floating rear axle. i strongly recomend the rear axle upgrade anyways, i just broke a 10 bolt carrier, which in turn ate the ring and pinion. that was with a dead stock 170,000 mi truck, and bald 29" tires. and no, i wasnt abusing it.



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