I have a 1984 Suburban with a J code 6.2 that I bought as a donor. Today I finally found and put a deposit on a 1990 Blazer 4x4 with a good running 5.7 EFI engine. The tranny is supposedly a Goodwrench overdrive with about 18K miles on it. That would be a 700R4, right? I plan to immediately yank out the gas motor and install the 6.2. A couple of questions: Will I be able to say to the DMV that this 6.2 is essentially the same as one that would have come stock in a 1990 Blazer? Did the military Blazers have J code engines? Next, will the gas 700R4 work well with the 6.2? Is the engine ECU separate from the transmission computer? The Suburban has a nicely working 700R4 also and I could switch it as well if worse comes to worse. I would rather use the transmission that is known to have low miles I guess. Also, will the vacuum pump from the 6.2 be sufficient to run the power brakes or will I have to switch over the the hydrovac unit? Any other comments are welcome as well.





Brian Roth, Pollock Pines, CA

That would be a 700R4, right?


Yes


Will I be able to say to the DMV that this 6.2 is essentially the same as one that would have come stock in a 1990 Blazer? .


Yes


Did the military Blazers have J code engines? .


Yes


Next, will the gas 700R4 work well with the 6.2? .


It can work, although the gasoline torque converter will have a higher stall speed than a torque convertor spec'ed for a diesel engine





Is the engine ECU separate from the transmission computer? .


No - the 1990 ECM controlled the lockup/unlocking of the transmission. The 700r4 can be controlled with a simple add on circuit.


Also, will the vacuum pump from the 6.2 be sufficient to run the power brakes or will I have to switch over the the hydrovac unit? .


I would not depend on the vacuum pump - although some have. I would swap over the hydroboost system. Edited by: azblazor

Thank you, azblazor. When you said


"It can work, although the torque converter will have a higher stall speed than a torque convertor spec'ed for a gas engine "


did you mean that the gas torque convertor will have a higher stall speed than the diesel one? Any idea if the 1982 diesel torque convertor will work in the 1990 transmission? I read somewhere that there were spline differences.


Again, thanks for the help.


Brian

Thank you, azblazor. When you said"It can work, although the torque converter will have a higher stall speed than a torque convertor spec'ed for a gas engine "did you mean that the gas torque convertor will have a higher stall speed than the diesel one? Any idea if the 1982 diesel torque convertor will work in the 1990 transmission? I read somewhere that there were spline differences.


Thanks, after reading what I wrote again, I did not phrase it correctly. The torque convertor for the diesel will have a lower stall speed to take advantage of a diesels torque lower it it's RPM range.


But that said, I have seen reports from guys (ARVEETEK I think was one) who have had sucess using a torque convertor from a gasoline engine, in a diesel application.


The torque convertor from an 84 or 82 700r4 would work in a 1990 700r4 as far as I know. As I am posting this I can't read your original post ....but I seem to remember that you said it was a "J" code diesel which would mean that it was a 3/4 ton and up. Therefore it would probably have had a TH400 behind it. That torque convertor will not work on a 700r4. The spline diferences of interest, are related to the output shaft, a TH400 has a 32 spline output shaft, a TH350 and a 700r4 have 27 spline output shafts, so they will not mate to the same transfer case with out swapping the transfer case input shaft and the adapter to the transmission.

Thanks. You have been a bunch of help. I guess I'll use the 1990 700r4. From what I have heard I'll have to find a way to make the torque convertor lock up. My suburban has a j code engine but it is a 1/2 ton. The vin says it should be a "c". I think the engine was changed at one point. The j code engine is bolted up to a 700r4 which does not have the electrical plug on the driver's side. I read somewhere that the torque convertor splines were different in different years but i guess I can figure that out when I get in there.





Brian

Keep in mind it will not pass emissions. Emissions at least in pennsylvania goes by what originally was in the vechile. I have an 82 camaro that i put a 70 chevell 350 motor in. It always goes by the 82 305 standards.





Eric

Interesting, I have a 1989 GMC K3500 4X4 6.2L turbo 400, that I want to put a 700R4 in, I never thought about the output shaft of the 700r4 will be diffrent, so I would have to find a transfer case out of a 3/4 ton that would have had the 700r4 in front of it,








Skippie

Here in California our emissions rules are a bit different. You can install an engine from a different vehicle but the new engine must be at least as new as the chassis. That is why I wanted to know if an early 80's 6.2 J code was essentially the same as a 1990 J code. It is also easier if the engine you are putting in was available in the vehicle from the factory, which it was.








Brian

Interesting, I have a 1989 GMC K3500 4X4 6.2L turbo 400, that I want to put a 700R4 in, I never thought about the output shaft of the 700r4 will be diffrent, so I would have to find a transfer case out of a 3/4 ton that would have had the 700r4 in front of it, Skippie


I don'ty think the 700r4 was ever put into a 3/4 ton or up (from the factory). There is no reason you need to keep the Transfer case from the TH400, you could just use the TC from the 700r4. If there is a reason to keep it (recently rebuilt,etc.), then you could tear it down and replace the 32 spline input shaft/gear with a 27 spline input shaft/gear.

Keep in mind it will not pass emissions. Emissions at least in pennsylvania goes by what originally was in the vechile. I have an 82 camaro that i put a 70 chevell 350 motor in. It always goes by the 82 305 standards. Eric


It would be a legal swap in Arizona. It would need to pass diesel emissions for the year and weight class of the frame/vehicle.