More TH350 to 700R4 conversion questions....

[scpike]

Hi everyone

I'm new to the forum altho I have have lurked here quite a bit .

I have a 1977 one ton G30 van that was converted to 4x4 out of the factory by a company called Pathfinder Equipment. Pathfinder went out of business about 25 years ago.

Anyway, I plan to replace the TH350 that is in it now with a 700R4. The axle ratio is 4.09 and I don't want to change that. I'm assuming that the existing TH350 transmission was the stock unit and that Pathfinder did not change it out as part of the conversion. I read R8rPhan's thread on a TH350 to 700R4 swap from earlier this month and that was quite helpful.

The TH350's tailshaft housing (it looks like it was a 6") was removed and replaced with an adapter to mate it to the NP205. A short tailshaft adapter was used on the tailshaft to get it to the proper length and change the spline count to 31 for the NP205. (see pictures)

The mounts on the transmission case are not used; instead the adapter between the NP205 and the TH350 served as the mounting point.

I (think) I know the following things:
1. I want a 88-93 700R4 "K" housing.
2. I need to pay special attention and get the TV cable installed and hooked up properly.
3. The 700R4 will add 2 3/8 inches to the length of the drivetrain and I'll need to move my mounting bracket back to accommodate that as well as cut new driveshafts.
4. The tailshaft housing bolt patterns of the TH350 and 700R4 are identical.
5. The output shafts of both transmissions have 27 splines.

My questions are:
1. Is it safe to assume that a 700R4 with a 6" tailhousing will have about a 6.5 inch tailshaft, the same as the TH350 shaft, and
2. What is the difference between a 2wd and 4wd 700R4?

Thanks in advance for any help. And I don't know much about transmissions, so if any of this sounds exceptionally stupid be gentle ;-)

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[HotRodPC]

Are you same guy that was from Alaska? We were talking **** and I think we scared that guy off. Just wondering if that's you so you come back with a different identity. He too has a 4x4 Van.

 

[HotRodPC]

Hi everyone

I'm new to the forum altho I have have lurked here quite a bit .

I have a 1977 one ton G30 van that was converted to 4x4 out of the factory by a company called Pathfinder Equipment. Pathfinder went out of business about 25 years ago.

Anyway, I plan to replace the TH350 that is in it now with a 700R4. The axle ratio is 4.09 and I don't want to change that. I'm assuming that the existing TH350 transmission was the stock unit and that Pathfinder did not change it out as part of the conversion. I read R8rPhan's thread on a TH350 to 700R4 swap from earlier this month and that was quite helpful.

The TH350's tailshaft housing (it looks like it was a 6") was removed and replaced with an adapter to mate it to the NP205. A short tailshaft adapter was used on the tailshaft to get it to the proper length and change the spline count to 31 for the NP205. (see pictures)

The mounts on the transmission case are not used; instead the adapter between the NP205 and the TH350 served as the mounting point.

I (think) I know the following things:
1. I want a 88-93 700R4 "K" housing.
2. I need to pay special attention and get the TV cable installed and hooked up properly.
3. The 700R4 will add 2 3/8 inches to the length of the drivetrain and I'll need to move my mounting bracket back to accommodate that as well as cut new driveshafts.
4. The tailshaft housing bolt patterns of the TH350 and 700R4 are identical.
5. The output shafts of both transmissions have 27 splines.

My questions are:
1. Is it safe to assume that a 700R4 with a 6" tailhousing will have about a 6.5 inch tailshaft, the same as the TH350 shaft, and
2. What is the difference between a 2wd and 4wd 700R4?

Thanks in advance for any help. And I don't know much about transmissions, so if any of this sounds exceptionally stupid be gentle ;-)

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But, don't run off. That's a cool van, and we want those here too.

So are you going to try and use the same adapters with the 700r4. You do have some interesting parts there. That 27 spline to 32 spline adapter is something I've never seen before.

 

[HotRodPC]

The only difference in a 2wd and 4wd 700r4 is the output shaft length. It almost sounds like you might need the 2wd unit though with all that adapter set up Pathfinder used, sounds like they used a 2wd Th350 with a 6in tailhousing, so you're going to have to try to make the 700r4 fill the same space unless you want to make some mods in crossmember location, and driveshafts.

 

[scpike]

Nope, not from Alaska - about 30 miles east of Denver in Colorado

She's a beast, to be sure. Most excellent in snow.

I was hoping to re-use the adapter if the 700R4 output shaft is the same.

 

[scpike]

The only difference in a 2wd and 4wd 700r4 is the output shaft length. It almost sounds like you might need the 2wd unit though with all that adapter set up Pathfinder used, sounds like they used a 2wd Th350 with a 6in tailhousing, so you're going to have to try to make the 700r4 fill the same space unless you want to make some mods in crossmember location, and driveshafts.

Yeah the key for me is to have enough tailshaft length to get through the tailshaft housing/NP205 adapter and to go to the 31 or 32 spline count (I can never get the same count twice) needed by the NP205.

A picture of the tailshaft housing/adapter is below. The NP205 is at the bottom and the TH350 was bolted to the top with no other tailshaft housing.

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[HotRodPC]

Yeah the key for me is to have enough tailshaft length to get through the tailshaft housing/NP205 adapter and to go to the 31 or 32 spline count (I can never get the same count twice) needed by the NP205.

A picture of the tailshaft housing/adapter is below. The NP205 is at the bottom and the TH350 was bolted to the top with no other tailshaft housing.

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I'll assure you, it's 32 spline. Same as Th400, Later SM465's, A833's etc. Yours is using a 27 spline to 32 spline adapter which also adds length. I'm wondering if a 2wd 700r4 won't be an exact fit, since the Th350 you're talking about has a 6in tailshaft.

 

[HotRodPC]

Nice, well don't run off. We consider those Squares too and we like variety. There within our year models etc. Now this Pathfinder conversion is something non OEM but we'll get it figured out. I think you'll have a good set up with the 4x4, 4.10 gears and a 700r4. You know the 700r4's are a bit weak, but you keep it cool, keep them 4.10's and your tires aren't extremely huge, I think you can make one live a fairly good life with a few mods to it and treat it right.

If you want, you can start up a Build thread and track your progress in the Under Construction section. Fair warning though, we like pics and want you to pic ***** the thread.

 

[scpike]

I'll assure you, it's 32 spline. Same as Th400, Later SM465's, A833's etc. Yours is using a 27 spline to 32 spline adapter which also adds length. I'm wondering if a 2wd 700r4 won't be an exact fit, since the Th350 you're talking about has a 6in tailshaft.

I'm hoping that a 700R4 will bolt up. Other than the TV cable issue and moving the mount back, is there anything else I should worry about or be aware of? How do you guys update the shift indicator on the steering column? These vans had the old school steering columns in them and the ignition key is still in the dash...

 

[HotRodPC]

BTW, what front axle do these have? 10 bolts? If I see that pic right, is it a Left Hand drop on the transfer case? I guess they'd have to do that since the engine is pushed to the right to make for floor space for the driver.

 

[scpike]

Nice, well don't run off. We consider those Squares too and we like variety. There within our year models etc. Now this Pathfinder conversion is something non OEM but we'll get it figured out. I think you'll have a good set up with the 4x4, 4.10 gears and a 700r4. You know the 700r4's are a bit weak, but you keep it cool, keep them 4.10's and your tires aren't extremely huge, I think you can make one live a fairly good life with a few mods to it and treat it right.

If you want, you can start up a Build thread and track your progress in the Under Construction section. Fair warning though, we like pics and want you to pic ***** the thread.

OK HotRodPC, I'll try to do that.

I plan to stick in a new motor too. and with all that I probably need to go through the NP205 and the GM corporate rear as well. It will be a summer project, I think.

Thanks for the info today. Much appreciated!!

 

[scpike]

BTW, what front axle do these have? 10 bolts? If I see that pic right, is it a Left Hand drop on the transfer case? I guess they'd have to do that since the engine is pushed to the right to make for floor space for the driver.

I believe its a Dana 60. It is a 10 bolt.

Yup, the 205 is the Ford version, and I think you're right. They just had to go the other way with it.

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[HotRodPC]

I believe its a Dana 60. It is a 10 bolt.

Yup, the 205 is the Ford version, and I think you're right. They just had to go the other way with it.

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Makes sense due to the engine on the right side. They planned that out pretty good. That's a Dana 44 front axle, also probably a Ford axle originally.

 

[scpike]

Interesting - Ford axle too, huh?

So you mentioned some mods for the 700R4 - what did you have in mind?

I'm trying to decide if I should build one myself. It would be my first transmission rebuild and I read somewhere that they are one of the tougher ones to rebuild.

But I've built my share of SBCs, so what the heck.....

If nothing else I'm the master of spending $15k on a $8k vehicle ;-)

 

[HotRodPC]

At the bare minumum for a 700r4 build. The Beast or Smartshell Sunshell, the Corvette Servo, An upgraded 3/4 clutch pack, A TransGo Jr shift kit that corrects a few issues and a trans cooler to go along as an addition to the radiator cooler.

Then you do other things like a wider 2/4 band, sleeve the input drum if you plan to turn some higher rpms. There's other mods too but it all depends on what you're doing with it if they're needed or not.