Tranny assistance needed. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Longhorn Man · 06-23-2002, 11:47 PM

Ok, if I do the Caddy 425 swap, i'm wondering if I should stay with the stock torque converter that is in the Longhorn now...or should I slap the 1900 stall that is in the GMC under the Longhorn.
I know the weight and gears and all that ca-ca matters, but I dunno how it effects it.
Any input from the gurus?

Longhorn Man · 06-24-2002, 12:02 AM

I seem to remember some discussion on BOP trannys and Chevy trannys interchainging on certian years...or year span... Any details?
I can't even remember what was so diferant between the 2. I know it is bolt patern on the bellhousing.
I just looked on the GMC, and there is a place for a bolt at the 12 O'clock position on the engine, but not the tranny.
I was unable to tell on the Longhorn becouse the motor is a bit further back to the fire wall. Maybe come daylight I'll be able to squeeze in there and see.
Anyone remember the differances?
If I can do it, I'd like to keep my rebuilt TH350 and ditch the ???mile old one that is bolted in there.

shortbed70 · 06-24-2002, 12:04 AM

I would say keep the conv. in it because that motor is built for low rpm torque so adding stall might bring it off the bubble on take of plus you would get better milage with the stocker. Is the motor stock or has it been modified. If mod. add stall if stock stay stock. My addvise,but I'm just a simple person!!

Longhorn Man · 06-24-2002, 12:18 AM

Quote:

just a simple person

LOL...Me too, that's why I am asking.
Thing is, a 1900 stall is a step over stock, and even though the 425 is stock, (it'll only have an aftermarket smaller carb and daul exhaust) I will still drive it like I am John Force.
Also, after driving my GMC with the 1900 verter in it, my observations are, in that truck, with that gearing, and that weight (all effects the stall RPM) seems to be a good unit for a stock, or mildly built engine.
I know future plans would include a small RV cam, and a daul plane intake. Maybe headers, but that would be a bit of cash since they would need to be fabbed. (I can't think of any stock offerings of a 425 in a pick-up

)

Longhorn Man · 06-24-2002, 04:41 PM

No one knows anything?

**MikeB** · 06-24-2002, 06:55 PM

I don't think your Chevy trans will bolt to the Cad motor. As for the T/C, a bigger motor=more torque=higher stall. So, if you now have a 350, going to a 425 would increase the stall speed maybe 100-200 rpm, assuming it has more torque just off idle.

If your T/C has lots of miles on it, I would spend around $100 and get a Hughes T/C from Scoggin Dickey. These things are built better than stock, with bearings where the stocker has bushings, etc. There's also the B&M version for $150. It would be a ***** to do all that work and then have your old T/C die.

Oh yeah, keep that stall speed below your 60mph cruise rpm, and GET A TRANS COOLER, because the trans will run hotter!

Longhorn Man · 06-24-2002, 07:38 PM

100 bucks...I wish I had a budget that big. (sad huh?) I have to work on a burger and fry budget here. (not even super size either)
You are right about the torque effecting the stall, but there is more to it than that, the weight and gearing plays a huge roll in it too.
The verter is a B&M unit, and even though I got it second hand, Fast told me it hardly has any miles on it. I just installed it in my truck a week or two ago, so I haven't even put hardly any miles on it.
Being a one ton, I am definatly not worried about my cruise RPM and a measly 1900 stall. Without popping the cover yet, i am thinking a 4.57 gear or so...but hoping (PRAYING) for something a little more freeway friendly. This Verter does well in my 3.07 28 inch tall tire GMC.

mooneyes · 06-25-2002, 09:38 PM

as of my knowledge the bolt pattern is the only difference in the bop tranny..as for the stall i would leave it out..as for gears i would hope for something higher than 4;57 also..my buddys chevillac..is a 1/2 ton 2wd longbed 500 cad auto 3:73 gears and the gears are almost to low..those motors have so much torque you dont need the gears.you can feel the thing pulling in the seat of your pants from 0 to 100 mph the torque is just unreal..he uses it to pull his car trailer with his 67 bb short bed on it with no problems at all the thing could pull a house

Longhorn Man · 06-25-2002, 09:41 PM

I think I have a 4.56 or so in the Longhorn.

weasel29gm · 06-25-2002, 11:21 PM

Hey LHORN my buddy put a 455 OLDS in a 76 4x4 i'll check wed eve on what t/c he used post ASAP

:

Longhorn Man · 06-25-2002, 11:43 PM

Thanks

weasel29gm · 06-26-2002, 08:46 PM

Just talked to him, he used the stock t/c out of a 400 turbo good up to 2200. Hope this helps!

06-23-2002, 11:47 PM	#1
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Tranny assistance needed. Ok, if I do the Caddy 425 swap, i'm wondering if I should stay with the stock torque converter that is in the Longhorn now...or should I slap the 1900 stall that is in the GMC under the Longhorn. I know the weight and gears and all that ca-ca matters, but I dunno how it effects it. Any input from the gurus?

06-24-2002, 12:04 AM	#3
shortbed70 Registered User Join Date: Mar 2002 Location: Forney TX Posts: 4,512	I would say keep the conv. in it because that motor is built for low rpm torque so adding stall might bring it off the bubble on take of plus you would get better milage with the stocker. Is the motor stock or has it been modified. If mod. add stall if stock stay stock. My addvise,but I'm just a simple person!! __________________ Troy 1965 Chevy Bagged,361 sbc,voodoo cam,1.5 full roller rockers,patriot 185cc vortec heads 2.02-1.60,vortec weiand polished intake,demon carb my truckhttp://67-72chevytrucks.com/vboard/s...d.php?t=332884 Big Red Dog build http://67-72chevytrucks.com/vboard/s...d.php?t=572274

06-24-2002, 06:55 PM	#6
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,597	I don't think your Chevy trans will bolt to the Cad motor. As for the T/C, a bigger motor=more torque=higher stall. So, if you now have a 350, going to a 425 would increase the stall speed maybe 100-200 rpm, assuming it has more torque just off idle. If your T/C has lots of miles on it, I would spend around $100 and get a Hughes T/C from Scoggin Dickey. These things are built better than stock, with bearings where the stocker has bushings, etc. There's also the B&M version for $150. It would be a ***** to do all that work and then have your old T/C die. Oh yeah, keep that stall speed below your 60mph cruise rpm, and GET A TRANS COOLER, because the trans will run hotter! __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!

06-25-2002, 09:38 PM	#8
mooneyes Registered User Join Date: Jan 2002 Location: Slippery Rock PA USA Posts: 1,692	as of my knowledge the bolt pattern is the only difference in the bop tranny..as for the stall i would leave it out..as for gears i would hope for something higher than 4;57 also..my buddys chevillac..is a 1/2 ton 2wd longbed 500 cad auto 3:73 gears and the gears are almost to low..those motors have so much torque you dont need the gears.you can feel the thing pulling in the seat of your pants from 0 to 100 mph the torque is just unreal..he uses it to pull his car trailer with his 67 bb short bed on it with no problems at all the thing could pull a house __________________ Ken Lyons, Slippery rock pa 68 short step 327 t10 4 gear 72 2wd blazer project 70 lwb 305/700r driver 78 caprice project 02 cavalier D.D ( hate it!!)

06-25-2002, 11:21 PM	#10
weasel29gm SLOW BUT SURE,BUT CLOSER Join Date: Feb 2002 Location: eleanor wv usa Posts: 3,096	Hey LHORN my buddy put a 455 OLDS in a 76 4x4 i'll check wed eve on what t/c he used post ASAP : __________________ 69 C-10, OWNED 38YRS... 350 over 30, 350 Turbo, 3:73 Posi P/S, P/B Black with red and black int. ''LOVE THESE OLD ''TRUCKS.......

06-24-2002, 12:02 AM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	I seem to remember some discussion on BOP trannys and Chevy trannys interchainging on certian years...or year span... Any details? I can't even remember what was so diferant between the 2. I know it is bolt patern on the bellhousing. I just looked on the GMC, and there is a place for a bolt at the 12 O'clock position on the engine, but not the tranny. I was unable to tell on the Longhorn becouse the motor is a bit further back to the fire wall. Maybe come daylight I'll be able to squeeze in there and see. Anyone remember the differances? If I can do it, I'd like to keep my rebuilt TH350 and ditch the ???mile old one that is bolted in there.

06-24-2002, 04:41 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	No one knows anything?

06-24-2002, 07:38 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	100 bucks...I wish I had a budget that big. (sad huh?) I have to work on a burger and fry budget here. (not even super size either) You are right about the torque effecting the stall, but there is more to it than that, the weight and gearing plays a huge roll in it too. The verter is a B&M unit, and even though I got it second hand, Fast told me it hardly has any miles on it. I just installed it in my truck a week or two ago, so I haven't even put hardly any miles on it. Being a one ton, I am definatly not worried about my cruise RPM and a measly 1900 stall. Without popping the cover yet, i am thinking a 4.57 gear or so...but hoping (PRAYING) for something a little more freeway friendly. This Verter does well in my 3.07 28 inch tall tire GMC.

06-25-2002, 09:41 PM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	I think I have a 4.56 or so in the Longhorn.

06-25-2002, 11:43 PM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Thanks

06-26-2002, 08:46 PM	#12
weasel29gm SLOW BUT SURE,BUT CLOSER Join Date: Feb 2002 Location: eleanor wv usa Posts: 3,096	Just talked to him, he used the stock t/c out of a 400 turbo good up to 2200. Hope this helps! __________________ 69 C-10, OWNED 38YRS... 350 over 30, 350 Turbo, 3:73 Posi P/S, P/B Black with red and black int. ''LOVE THESE OLD ''TRUCKS.......

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