Are transmissions 'rated' for certain hp?

littlekings · 12-21-2005, 12:56 PM

When swapping a SBC for a BBC is there any concern as to whether or not the tranny can handle the bigger engine? I've got a 5 speed manual in a 88 2500 originally came with 305. I don't intend to stomp on it but I do tow a car and haul things on occasion.

390FE · 12-21-2005, 01:18 PM

I'm prety sure there is a rating but not sure what they are.

I do know that for example the 5 speed manual in a Ford Focus(car) can handle more power(torque and HP) than the automatic. And back in the 60's and 70's a manual in a truck was tougher than an auto.

But in todays trucks the auto's are rated tougher than the manuals, in the light duty trucks anyway. I looked into getting a 2005 F150 and to get the HD package I had to get an auto in it. Nevermind that a manual was not even an option in 2005. I bought an 87 toyota instead, what a trade off

He's away for a while(holiday vacation) but Chevyguy sould be able to answer your question real easily.

mrjohnwayne · 12-25-2005, 09:50 PM

No. If you are running both motors on the stock setup, there should be no harm. If you plan on running some serious power outta the bbc then you should consider on a rebuilt with a few stouter parts but nothing mahor

John_and_Donna · 12-28-2005, 06:40 PM

Yes, most trransmissions are "rated" for certain power levels. However, the rating really isn't dependent on horsepower; it is most dependent on torque. Trannies are usually rated for a certain amount of torque, then that also translates to a certain horsepower.

The internals of many manual trannies are strong enough to take a lot of abuse. The first weak link is most often the clutch. Going to a BBC from a 305 will put a lot more stress on the clutch. It would be better to upgrade the clutch and flywheel to one made for a BBC, however, that may not fit the splines on your existing input shaft.

Itstali25 · 12-29-2005, 01:35 AM

yeah going from a 305.........sad engine, i have one so i know how sad mine is, to a BBC will put alot more stress on it, listen to what JAD (John and Donna) said, clutch prolly wouldn't hurt, dunno if anything else

John_and_Donna · 12-30-2005, 07:25 PM

littlekings,

I did some parts checking today and discovered that GM used the same 5-speed transmissions for SBC and BBC trucks in 1988. This means that your tranny will work behind a BBC just fine unless the motor is "built to the hilt" and you are really driving aggressively all the time.

The only things I can really think of to upgrade would be the clutch assembly as I stated above. A BBC clutch assembly should work just fine with your tranny as the splines should be the same (since the same tranny was used for BBC applications). You may also need to upgrade the slave cylinder (I think the 88's have hydraulic clutches). A quick trip to your local chevy dealer can confirm this..... go to the parts counter and have them check the part # for the SBC and BBC applications. If the same # is used, then you are OK. If not, then upgade to the BBC part #.

Hope this helps...

12-21-2005, 12:56 PM	#1
littlekings Junior Member Join Date: Dec 2005 Location: NE Ohio Posts: 4	Are transmissions 'rated' for certain hp? When swapping a SBC for a BBC is there any concern as to whether or not the tranny can handle the bigger engine? I've got a 5 speed manual in a 88 2500 originally came with 305. I don't intend to stomp on it but I do tow a car and haul things on occasion.

12-25-2005, 09:50 PM	#3
mrjohnwayne Moderator Join Date: Apr 2005 Location: Texas Posts: 3,220	No. If you are running both motors on the stock setup, there should be no harm. If you plan on running some serious power outta the bbc then you should consider on a rebuilt with a few stouter parts but nothing mahor __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

12-29-2005, 01:35 AM	#5
Itstali25 Senior Member Join Date: Jul 2004 Location: Southern Missouri Posts: 708	yeah going from a 305.........sad engine, i have one so i know how sad mine is, to a BBC will put alot more stress on it, listen to what JAD (John and Donna) said, clutch prolly wouldn't hurt, dunno if anything else __________________ http://www.cardomain.com/ride/644045 Trucks are just cars when they grow up!!! If your gunna get a truck....Get a TRUCK!!

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12-21-2005, 01:18 PM	#2
390FE Senior Member Join Date: Sep 2005 Location: S. NH Posts: 336	I'm prety sure there is a rating but not sure what they are. I do know that for example the 5 speed manual in a Ford Focus(car) can handle more power(torque and HP) than the automatic. And back in the 60's and 70's a manual in a truck was tougher than an auto. But in todays trucks the auto's are rated tougher than the manuals, in the light duty trucks anyway. I looked into getting a 2005 F150 and to get the HD package I had to get an auto in it. Nevermind that a manual was not even an option in 2005. I bought an 87 toyota instead, what a trade off He's away for a while(holiday vacation) but Chevyguy sould be able to answer your question real easily.

12-28-2005, 06:40 PM	#4
John_and_Donna Full Member Join Date: Nov 2005 Location: San Antonio, TX Posts: 22	Yes, most trransmissions are "rated" for certain power levels. However, the rating really isn't dependent on horsepower; it is most dependent on torque. Trannies are usually rated for a certain amount of torque, then that also translates to a certain horsepower. The internals of many manual trannies are strong enough to take a lot of abuse. The first weak link is most often the clutch. Going to a BBC from a 305 will put a lot more stress on the clutch. It would be better to upgrade the clutch and flywheel to one made for a BBC, however, that may not fit the splines on your existing input shaft.

12-30-2005, 07:25 PM	#6
John_and_Donna Full Member Join Date: Nov 2005 Location: San Antonio, TX Posts: 22	littlekings, I did some parts checking today and discovered that GM used the same 5-speed transmissions for SBC and BBC trucks in 1988. This means that your tranny will work behind a BBC just fine unless the motor is "built to the hilt" and you are really driving aggressively all the time. The only things I can really think of to upgrade would be the clutch assembly as I stated above. A BBC clutch assembly should work just fine with your tranny as the splines should be the same (since the same tranny was used for BBC applications). You may also need to upgrade the slave cylinder (I think the 88's have hydraulic clutches). A quick trip to your local chevy dealer can confirm this..... go to the parts counter and have them check the part # for the SBC and BBC applications. If the same # is used, then you are OK. If not, then upgade to the BBC part #. Hope this helps...