Two Questions....

Iceninekills · 08-24-2009, 05:10 PM

Hey guys! I have a couple questions regarding my 1985 GMC Sierra classic. First off, my truck came with a 3 speed automatic. Or at least i'm pretty sure it's a three speed, all I know is it didn't come with overdrive. My question: Is there a tranny that has overdrive and can mate up with my four wheel drive that I can put in this truck? I do a lot of driving in this thing and I think i'm only going to do more as time goes on, so overdrive would be nice. My next question: I have a small leak on the power steering box at the seal where the shaft from the steering wheel goes into the box. is it easier to just replace the box or pop out the seal? because it looks annoying to get out.
Anyways, any help is appreciated. Thank you very much.

summit · 08-24-2009, 06:29 PM

I'd think long and hard before replacing that 3 spd auto. It was the last good transmission gm made for their 1/2 tons. All the 4 spds have issues.

stumpuller454 · 08-24-2009, 06:43 PM

if you got a th-400 an adapter would be needed, plus most likley crosmmeber fab and shaft lenght issues.

as for the box leak i don`t beleive they would be too bad... but i`ve never done one tho.

BernieB · 08-24-2009, 07:12 PM

I do believe there's a unit that will replace the tailpiece on that to give you overdrive. Let me find the link... Here we go...

Gear Vendors under/overdrive transmissions the most awarded auxiliary transmissions.

For the '88 TH400 the part number would be Part #3D0241A

I've seriously considered getting one of these for my GMC C3500

Iceninekills · 08-25-2009, 12:40 AM

I already did think long and hard on it lol. And mine is a 3/4 ton. I really like the 700R4, and I found a site from a company who sells performance built ones, 700R4 Transmission, Remanufactured, 4x4, Super, Heavy Duty, 4WD, - REBUILT TRANSMISSION GM, Chevrolet 700R4 Super Sport - Monster Transmission & Performance | 800-708-0087 | Fast FREE Shipping! this is the one I found. The link here goes to the best one they offer and it's under $1400. So i'm going to have to modify a bunch of stuff under there to fit the tranny?

And Good grief! that kit from Gear Vendors costs more than anything else i'd wanna do on my truck lol.

leolkfrm · 08-25-2009, 06:33 AM

but gear venders will hold up and the only mod is the driveshaft

BernieB · 08-25-2009, 06:56 AM

Quote:

Originally Posted by Iceninekills

And Good grief! that kit from Gear Vendors costs more than anything else i'd wanna do on my truck lol.

Yeah, the price is the main reason I haven't gotten a unit for my truck. I already have overdrive, but because of the 4.10 rear my RPMs are around 2200 @ 65 mph, which kills my fuel economy. With one of these I'd be able to drop it down to 1900, which would probably boost my MPG from 12 up to around 15 on the highway. At that rate it'd take about 80,000 miles to break even on it.

summit · 08-25-2009, 12:15 PM

Yea many hard core 4wd folks like the 700R4 for the low 1st gear. Having gone through 3 in 150,000 km I just can't endorse that transmission. Each rebuild included additional mods, shift kits, more clutch plates etc. Different shop each time. Just seems like an attempt to fix a bad design. Maybe they finally figured it out. The th400 had a rep for being real strong. The gear vendors mod is expensive but niiccceee. Good luck with it.

08-24-2009, 05:10 PM	#1
Iceninekills Full Member Join Date: Oct 2007 Posts: 15	Two Questions.... Hey guys! I have a couple questions regarding my 1985 GMC Sierra classic. First off, my truck came with a 3 speed automatic. Or at least i'm pretty sure it's a three speed, all I know is it didn't come with overdrive. My question: Is there a tranny that has overdrive and can mate up with my four wheel drive that I can put in this truck? I do a lot of driving in this thing and I think i'm only going to do more as time goes on, so overdrive would be nice. My next question: I have a small leak on the power steering box at the seal where the shaft from the steering wheel goes into the box. is it easier to just replace the box or pop out the seal? because it looks annoying to get out. Anyways, any help is appreciated. Thank you very much.

08-24-2009, 07:12 PM	#4
BernieB Senior Member Join Date: Jul 2009 Location: Fredericksburg, VA Posts: 1,910	I do believe there's a unit that will replace the tailpiece on that to give you overdrive. Let me find the link... Here we go... Gear Vendors under/overdrive transmissions the most awarded auxiliary transmissions. For the '88 TH400 the part number would be Part #3D0241A I've seriously considered getting one of these for my GMC C3500 __________________ If the guys who design 'em had to take one home, use it every day for 2 years, and do all the maint and repairs themselves, cars would have a button on the dash to change the oil, filters & plugs. Last edited by BernieB; 08-24-2009 at 07:15 PM. Reason: Added part number

08-25-2009, 06:33 AM	#6
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 4,300	but gear venders will hold up and the only mod is the driveshaft __________________ 4 wheels move the body 2 wheels move the soul B.W.A.I

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08-24-2009, 06:29 PM	#2
summit Full Member Join Date: Jun 2009 Posts: 33	I'd think long and hard before replacing that 3 spd auto. It was the last good transmission gm made for their 1/2 tons. All the 4 spds have issues.

08-24-2009, 06:43 PM	#3
stumpuller454 Senior Member Join Date: Dec 2007 Location: Grande Prairie, AB Posts: 2,043	if you got a th-400 an adapter would be needed, plus most likley crosmmeber fab and shaft lenght issues. as for the box leak i don`t beleive they would be too bad... but i`ve never done one tho. __________________ SUPERCHARGED 454 K2500 GMC! 450hp and 600ft/lbs http://www.youtube.com/watch?v=WJ27RJHfJKE "sailing with Captain Morgan often!"

08-25-2009, 12:40 AM	#5
Iceninekills Full Member Join Date: Oct 2007 Posts: 15	I already did think long and hard on it lol. And mine is a 3/4 ton. I really like the 700R4, and I found a site from a company who sells performance built ones, 700R4 Transmission, Remanufactured, 4x4, Super, Heavy Duty, 4WD, - REBUILT TRANSMISSION GM, Chevrolet 700R4 Super Sport - Monster Transmission & Performance \| 800-708-0087 \| Fast FREE Shipping! this is the one I found. The link here goes to the best one they offer and it's under $1400. So i'm going to have to modify a bunch of stuff under there to fit the tranny? And Good grief! that kit from Gear Vendors costs more than anything else i'd wanna do on my truck lol.

08-25-2009, 12:15 PM	#8
summit Full Member Join Date: Jun 2009 Posts: 33	Yea many hard core 4wd folks like the 700R4 for the low 1st gear. Having gone through 3 in 150,000 km I just can't endorse that transmission. Each rebuild included additional mods, shift kits, more clutch plates etc. Different shop each time. Just seems like an attempt to fix a bad design. Maybe they finally figured it out. The th400 had a rep for being real strong. The gear vendors mod is expensive but niiccceee. Good luck with it.