700R4 swap in M1009?

[Mike_Pop]

Has anyone done a tranny swap from the TH400 to a 700R4? There is a guy near me who is parting out two civi Blazers and they both have the 700R4 transmissions.

Thanks!

Mike Pop

 

[fordlotus]

I've been down that road a few times. I'm not by any means an expert but just have learned from experience and trial and error on these tranys. I will help to the best of my knowledge. Between my dad and I we keep 3 of the m1009s running with two parts m1009's as support. We bought the military parts vehicles because we had a transfer case and also a trany go out before in seperate instances (among other parts). We learned after pulling apart a civilian blazer, a suburban, and a civilian 1 ton, all 4x4, all but blazer diesel, that nothing we pulled out would work in the m1009s for the trany or transfer case. For starters, make sure to use a diesel torq converter (assuming you still have the 6.2 in yours) no matter what you put back into your truck. Make sure to take your flywheel and match it up to what you buy when you replace it becuase there was an issue with this too. But you won't get this far without military parts because the spline numbers are different. I may be mistaken but I think the military stuff was all 36 spline and the civilian stuff was 32. I suppose if you replaced the trany, transfer case, flywheel, and torq converter you may make it work, but I'd be willing to bet one of the mechaincs on here are going to tell you there are big differences internaly to a gas trany and a diesel trany. I seriously doubt those 700s could take near the beating a 400 could.

 

[Adamlee]

Has anyone done a tranny swap from the TH400 to a 700R4?
Mike Pop

Mangus580 (Mike the Moderator Man) has a CUCV M1009 (Blazer) with a 700R4 swap. He likes it....ask him about it.

Adam Lee

 

[Recovry4x4]

RE: Re: 700R4 swap in M1009?

The 700R4 won't take the abuse of the 400 but it will hold up just fine to a 6.2. A quality rebuilt 700R4 is actually a pretty good tranny.They will require a torque converter specific to a diesel application. Rizzo has also done this swap but with a M1008 so he might have some info to add. It can be done and works well when it is.

 

[Mike_Pop]

What would be the fuel consumption with the overdrive tranny? Does it improve? If it isn't by much, then I wouldn't do the swap.

Mike Pop

 

[mangus580]

I've been down that road a few times. I'm not by any means an expert but just have learned from experience and trial and error on these tranys. I will help to the best of my knowledge. Between my dad and I we keep 3 of the m1009s running with two parts m1009's as support. We bought the military parts vehicles because we had a transfer case and also a trany go out before in seperate instances (among other parts). We learned after pulling apart a civilian blazer, a suburban, and a civilian 1 ton, all 4x4, all but blazer diesel, that nothing we pulled out would work in the m1009s for the trany or transfer case. For starters, make sure to use a diesel torq converter (assuming you still have the 6.2 in yours) no matter what you put back into your truck. Make sure to take your flywheel and match it up to what you buy when you replace it becuase there was an issue with this too. But you won't get this far without military parts because the spline numbers are different. I may be mistaken but I think the military stuff was all 36 spline and the civilian stuff was 32. I suppose if you replaced the trany, transfer case, flywheel, and torq converter you may make it work, but I'd be willing to bet one of the mechaincs on here are going to tell you there are big differences internaly to a gas trany and a diesel trany. I seriously doubt those 700s could take near the beating a 400 could.

You are comparing a little bit of apples to oranges above here.....

The military TH400 is the same as the civvy TH400, as with the NP208 Tcase. The spline counts are the same... Its the same stuff. Your issuse might stem from 1/2 ton civvy vehicles mostly came with the 700R4 in the 80's (or the manual), while the 1 ton mostly came with the NP205 Tcase.

A 700R4 can be built to be almost as strong as a 400 now... (not quite, but almost)...


Mike, as to your questions, we need some more info about the civvy donors:

• What engine do they have?
• 2wd or 4wd?
• What vehicle? (not that it matters much)

Things that you will need from the donor:

• Tranny (obvious)
• Transfercase Pedastal
• Transfercase input spline (almost easier to take the whole case if its good)
• PRNDL Plate in the dash
• Any Lockup Wiring for the Torque Converter (not 'required' but helpful)
• TV Cable & bracketry

Things I would suggest replacing (or adding):

• Flex Plate (can be used from donor... but they are cheap enough and ideal to replace[/lis]]
• Torque Converter
• Input Seal
• External Cooler
• Tranny Temp Guage

Its mostly a direct swap. Basic process is to drop the old tranny & tcase, replace flex plate, and put new tranny & case in. Connect & adjust TV cable. Install any 'add-ons'. Replace PRNDL indicator (not done in mine yet)

Its a great swap..... BUT with the 3.08 gears, for daily driving you wont be as happy with it as you would expect. The 6.2 isnt in the right RPM range to really have any power at all when in OD at about 55mph, especially with the Torque Converter locked up. Honestly, Along with this swap, I would suggest doing a gear change as well, to at least 3.42, but preffering the 3.73. That said, I have had mine done for a year now, and I still have the stock gears. I did not see a mileage improvement, but thats probably the way I drive, and the amount the engine lugs because of the gears.

Also, if the donor tranny is unknown, have a good rebuild shop run through it. It will save you headaches in the future, I am sure.

Hope this helps, and would be glad to answer any more questions.

 

[AJMBLAZER]

Guys with civilian diesel K5's with 700R4's have reported as much as 25mpg on the highway with stock setups. 20mpg around town isn't uncommon either.
The 6.2L isn't a powerhouse but it is a fuel miser.

 

[BKinzey]

I'm one of those guys Bought a Blazer, 6.2, 700r4, 3.73, 4X4, and 31" tires. Drove it 900 miles home and got 25mpg all the way at 65mph

Ignoring it old adage "If it ain't Broke don't Fix It!" It's been a donor to the FrankenWhatever I'm currently building

X2 to what Mangus580 said.

 

[CCATLETT1984]

I may be mistaken but I think the military stuff was all 36 spline and the civilian stuff was 32.

All of the CUCV's have 32spline ouputs on the transmissions. as does every th400 out of a 1ton pickup, the 700r4 is more rare to find a 32spine, but the output shaft can be changed out.

 

[superburban]

I went the other route. I swapped out an old 700R4 for a TH400. One thing you need to do on this swap is change the TPS on the injector pump. The 700 closes the circuit on WOT, but the 400 opens the circuit on full throttle. I killed the 700 because I installed a used IP with the 400's TPS on it. I was not aware of the difference at the time. Immediately after the IP swap, I noticed that the truck would try to lurch forward at stoplights. I thought it was a problem with the new IP, only to realize after the tranny died that the torque converter was trying to lock up when I stopped, and unlocking at cruising speeds. OOPS!