700R4 Crapped out, should I swap?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Jesse

Junior Member
Joined
Mar 22, 2014
Posts
6
Reaction score
0
Location
Springfield IL
First Name
Jesse
Truck Year
1985
Truck Model
k10
Engine Size
350
I recently purchased an 85 K10 a few weeks ago, I love it. I've replaced all the maintenance parts through out, and have around $4k budgeted which I was going to use on the paint. Unfortunately the 700R4 took a **** and I'm looking at $1200-1900 on a trans or rebuild. I'm curious if I should just go ahead with the 5.3/4l60e swap now and is it possible to stay within that $3-4k range. I have local yards with them available for around $1,500. I don't want anything special, its just going to be a weekend driver. Maybe 6,000 miles a year. Any advice help is greatly appreciated.
 

HotRodPC

Administrator
Staff member
Admin
Joined
Aug 29, 2010
Posts
47,132
Reaction score
9,329
Location
OKC, OK
First Name
HotRod
Truck Year
85 K20 LWB
Truck Model
Silverado
Engine Size
454 - Turbo 400 - 3.73
An 85 700r4 isn't one of the desirable units but as far as strength, the 4L60-E is lateral to the 700r4. The 4L60-E might have more bug fixes corrected but that's really the only advantage IMO. The electronics just create a different set of things that can go wrong vs the TV cable and governor. They are about the same with the huge difference the valve bodies. 1 is electronic, 1 is not.
 

Jesse

Junior Member
Joined
Mar 22, 2014
Posts
6
Reaction score
0
Location
Springfield IL
First Name
Jesse
Truck Year
1985
Truck Model
k10
Engine Size
350
I appreciate the reply. I've been reading for weeks on the swap, but like I said I'm on a budget, enough to get 700r4 fixed and strengthened for $1,600 and roll with the 350 'til later this year and swap a vortec, for a vortec/700r4 combo. |

..Or I can start with a $1,200 vortec/4l60e pull out swap and drop it in for not much more I'll go that route. I'm more or less weighing the cost/reward and trying to get an idea from the swap guys if $3-4k is enough to get the swap done and good to go. Thanks for the advice.
 

HotRodPC

Administrator
Staff member
Admin
Joined
Aug 29, 2010
Posts
47,132
Reaction score
9,329
Location
OKC, OK
First Name
HotRod
Truck Year
85 K20 LWB
Truck Model
Silverado
Engine Size
454 - Turbo 400 - 3.73
I appreciate the reply. I've been reading for weeks on the swap, but like I said I'm on a budget, enough to get 700r4 fixed and strengthened for $1,600 and roll with the 350 'til later this year and swap a vortec, for a vortec/700r4 combo. |

..Or I can start with a $1,200 vortec/4l60e pull out swap and drop it in for not much more I'll go that route. I'm more or less weighing the cost/reward and trying to get an idea from the swap guys if $3-4k is enough to get the swap done and good to go. Thanks for the advice.

Your plan to buy a good used running Vortec/4L60-E makes perfect sense to me. If you're going to spend the money anyway, it's a trade off for a new 700r4 for a USED Vortec/4L60-E, but you're getting what you want and going in the direction you intend to go in the future anyway. That's the way I think alot and why I put so many things off. Just beware, as said, it's a trade off for a NEW 700r4 for USED what you want. That 4L60-E might only last you a few months or even worse. However, I still say go for it, and if you get a few months out of it, then you should have financially recovered from the initial USED powertrain purchase and be able to get the 4L60-E rebuilt.

BTW, don't tell anyone here, but I've got a TBI motor and 700r4 that needs some used heads and head gaskets on it, and the ECM, wiring harness and all. I'm going to keep this TBI set up cuz I damn sure not going to throw it away, and the Single pc Rear Main seal core motor, and the Serpentine set up on the front of the motor I can use on my newer crate motor 350, but I think I've changed my mind again in your direction. I eventually want Vortec or LS, so I'm thinking if I have to put some cash into the used heads on a 219,000 mile TBI motor that may only last another 20-30,000 miles, and I'm going to have to go through all the labor to install the wiring harness and ECM, I might as well just wait and see if I can find a good running Vortec Set Up instead. However, I think I'll go with the Vortec motor, but still run the 700r4. Being the same ECM does control the 4L60-E, I'll have the option to update to 4L60-E if I so choose since they outside dimensions on the 2 are exactly alike. Same driveshafts, mounts, shift linkage and all is the same. I'll just have to use the Electronic Speedo 700r4 which I have. And for you, do keep in mind you need to find an Electonic Speedo Cluster if you're going to run the 4L60-E. Should be in 89-91 Burbs, Crew Cabs and K5 Blazers. You won't be running a speedo cable at all.
 

Jesse

Junior Member
Joined
Mar 22, 2014
Posts
6
Reaction score
0
Location
Springfield IL
First Name
Jesse
Truck Year
1985
Truck Model
k10
Engine Size
350
I may actually just go with the rebuilt 700, swap a vortec to it later this year, and if I don't like it a 4l60e next year, lol. Thanks for the headsup.
 

HotRodPC

Administrator
Staff member
Admin
Joined
Aug 29, 2010
Posts
47,132
Reaction score
9,329
Location
OKC, OK
First Name
HotRod
Truck Year
85 K20 LWB
Truck Model
Silverado
Engine Size
454 - Turbo 400 - 3.73
I may actually just go with the rebuilt 700, swap a vortec to it later this year, and if I don't like it a 4l60e next year, lol. Thanks for the headsup.

Not a bad idea either. Then you have a known, should be dependable trans. All you'd do is not use the Trans portion of the ECM like a manual trans would do for your Vortec ECM, then set up the TV cable of your 700r4 and use the Vac Switch on the firewal for lock up on the converter just like the OEM carbed 700r4's used, or an aftermarket converter lock up method. Certainly doable. You don't have to have the E controlled trans just cuz the motor is. That's the great thing with these Squares and the way GM makes transitions. You can easily go carbed and old school auto, or TBI or SFI (Sequential Fuel Injection, used on Vortec) with either old school or E trans. Being that the 700r4 and 4L60-E are not the strongest option, if you're going Vortec you should really consider a 4L80-E transmission to go behind your Vortec. 4L80-E can be controlled by your Vortec ECM and is about as rock solid as a Th400 except that it has an OD.
 

yevgenievich

Full Access Member
Joined
Mar 1, 2014
Posts
4,820
Reaction score
3,402
Location
Place
First Name
Name
Truck Year
Year
Truck Model
Model
Engine Size
Size
$3-4k is enough to get ls 5.3 with 4l60e including harness and computer and conversion parts. I would go with ls used parts, try to find a lower mileage or known owner set. I have done ls1+4l60e swap 4-5 years ago on my trans am for a total of $3.5k, three years later 4l60e failed, and now it has t56
 

87lsxgmc

Member
Joined
Oct 31, 2013
Posts
37
Reaction score
1
Location
buffalo
First Name
Paul
Truck Year
1987
Truck Model
2500
Engine Size
5.3
5.3s with all accessories can be found pretty cheap. mileage wouldnt scare me if it has good compression, i took my 5.3 apart with 170k, and the cyl walls look like they just got back from the machine shop. its easy to modify the harness. i havent had much luck with my 4l60e in my 2000 silverado, blew it up 3 times. usually the 'beast' sunshell takes care of the problem for most guys, i still snapped the beast hauling my car to the track. if your rear axle ratio isnt too steep i would stick with a th350 if its going to be a weekend warrior/fair weather cruiser. they can take alot more abuse.
 

Latest posts

Forum statistics

Threads
44,460
Posts
958,379
Members
36,845
Latest member
mudshark7
Top