89 700r4 upgrade

[ChrisT2006]

Hey guys, I’m new to the forum, so any help would be appreciated. I have a 1989 k1500 with a 700r4 that is about to die. It has trouble shifting, slips in overdrive, etc. I would like a manual, like a nv3500, but I don’t know if that’s even doable, I know I probably need a new transfer case, driveshaft, etc. Basically my question is this: what would y’all recommend me do in this situation? Buy a remanufactured 700r4? Or go with a different automatic option? Or should I go with a manual swap? I’d like to keep the cost under $3,000.
Thanks

 

[Erik the Awful]

What's your purpose for this truck? An NV3500 swap is doable and the parts should be a bolt-in. The difficult part is finding all the parts. You'll need the early clutch pedal assembly, the clutch hydraulics, the flywheel, a clutch kit, the transmssion (usually in a salvage yard the shifters and shift towers are robbed), the shift tower gasket, the shift tower top, the shift lever, and the right gear oil for the transmission.

If you're going to be doing towing or racing, step up to either a TH400 or a 4L80. The TH400 was offered in '89 and will be mostly a bolt-in. The 4L80 came later and is computer controlled, so you'd need a stand-alone controller. The upside is that it's the strongest transmission available and you don't have to worry about TV cable adjustment.

The easy button is to swap in a rebuilt 4L60/700R4. They're weak, but just fine for moderate daily driver pickup duties. Personally, I don't think a rebuilt 4L60 is worth the $2000+ they usually cost. I managed to find somebody to rebuild my 4L60 cheap, and when I get it swapped in I'll find out if it was worth it.

 

[ChrisT2006]

I found a junkyard nv4500 with transfer case for $800, I’m looking at that. My purpose for the truck? A reliable daily driver, yet fun to drive. That’s why I’m looking at a manual. You’re right, there’s no way I’m paying $1,700+ for a rebuilt 4l60. I’ll look at the TH400

 

[NickTransmissions]

I found a junkyard nv4500 with transfer case for $800, I’m looking at that. My purpose for the truck? A reliable daily driver, yet fun to drive. That’s why I’m looking at a manual. You’re right, there’s no way I’m paying $1,700+ for a rebuilt 4l60. I’ll look at the TH400

$1700 is market rate for a 700R4 bench overhaul and is worth it provided the right things are done with the trans and it comes with a new torque converter...Th400 would be going backwards but if you hardly ever drive on the highway, its probably an easier swap than a manual trans.

 

[Erik the Awful]

I found a junkyard nv4500 with transfer case for $800, I’m looking at that.

The price is a bit steep, but NV4500s are hard to find. If I were wanting a strong manual, I'd be all over that.

Th400 would be going backwards but if you hardly ever drive on the highway, its probably an easier swap than a manual trans.

It was the HD transmission in '89, so I don't see it as a step backwards, but yes, fewer gears than the 4L60.

 

[NickTransmissions]

The price is a bit steep, but NV4500s are hard to find. If I were wanting a strong manual, I'd be all over that.


It was the HD transmission in '89, so I don't see it as a step backwards, but yes, fewer gears than the 4L60.

Id save the TH400 HD unit for a more serious duty application unless the OP is doing some heavy towing/hauling/working and doesn't need the OD ....just a difference of opinion...

ETA - OPs final drive ratio should also be considered for doing a TH400 swap...If he has a 3.08 ratio, it's prob fine but 3.23 or higher, he's going to be seeing an excessive amount of RPMs on the hwy in 3rd...

 

[ChrisT2006]

Id save the TH400 HD unit for a more serious duty application unless the OP is doing some heavy towing/hauling/working and doesn't need the OD ....just a difference of opinion...

ETA - OPs final drive ratio should also be considered for doing a TH400 swap...If he has a 3.08 ratio, it's prob fine but 3.23 or higher, he's going to be seeing an excessive amount of RPMs on the hwy in 3rd...

So you think the NV4500 will work? Will I have to modify my driveshaft length? The one I’m looking at comes with the transfer case btw

 

[NickTransmissions]

So you think the NV4500 will work? Will I have to modify my driveshaft length? The one I’m looking at comes with the transfer case btw

I'm not familiar with the NV series of manual transmissions, never having worked on them before so can't comment on whether it will work. But generally speaking, most trans swaps require some driveline work including cutting and re-balance....A local driveline shop can do all of it plus replace the u-joints so you have a shaft that's 100% good to go.

 

[Ace17]

Yep, the auto to manual swap is definitely doable. I actually did one on my 88' GMC k1500.

So it really all depends on how much you want a manual. If you just kinda want one, I might look at getting the rebuilt auto. It's a lot easier. But if you LOVE manual cars and trucks like I do, and you're willing to put in the work, I'd do it. It's a little laborious, but it's a labor of love.

As someone else mentioned, you're gonna need to pull the flywheel, clutch, pressure plate, clutch pedal assembly, throwout bearing, pilot bearing, clutch fork, neutral safety swtich, and trans from the donor truck. This is a 4x4 truck, right? You'll also need to swap out your 28 spline input shaft on your transfer case to a 32 spline input shaft - this is something people don't mention a lot. No need to buy a whole new transfer case, just open it up, swap out the input shaft, and you're good.

I should also mention, I totally understand being on a budget, but there are some things you might want to buy new, like the clutch, pressure plate, pilot bearing/bushing, maybe even the master/slave cylinder. Flywheel can be resurfaced.

Also, I would try and nail down what you're gonna use the truck for. I think the nv4500 is an awesome bulletproof trans, and it's pretty damn hard to find, but if you're looking for "fun", you might be disappointed, especially if this is mainly a street truck, and you're not doing any hauling/pulling. That 1st granny gear feels like a slug off of the line. Even with the nv3500, it's a truck trans, so 1st gear still feels steep, and a little slow off the line, but the nv4500 is even steeper. I would say the nv3500 is a good choice for a regular street truck, and a t56 is GREAT for a 2wd street truck . The gear ratios definitely contribute to the drivability.

Oh, and it might be helpful to swap out the computer, as the PROMs for autos and manuals are a little different. Just go to the junkyard, pull out the glove box, and get to the computer. Pretty easy

 

[Erik the Awful]

Oh, and it might be helpful to swap out the computer, as the PROMs for autos and manuals are a little different. Just go to the junkyard, pull out the glove box, and get to the computer. Pretty easy

'89 had a 4L60, not a 4L60E, so the only care the computer has about the transmission is an output to the torque converter clutch. AFAIK it doesn't even take a reading from the VSS. If it's programmed any differently, I don't think it will endanger your ECM, transmission, nor engine.