BC - TEXAS
Registered Member
I have a '70 K5 and access to an '87 Blazer. I want to convert to front discs and the parts are all good...can I use the OD Trans/Transfer case in my '70?
CK5
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HELP!! '70 and '87 K5 Question!!
- Thread starter BC - TEXAS
- Start date
is the 87 in good shape?
You’ll have to move the transmission crossmember which will likely require new driveshafts front and rear
Be sure the get the entire tcase shifter assembly.
For the brakes everything should bolt on. I’m not sure if the 2 trucks use the same wheel bearings but worst case just swap the spindles too. Don’t forget the brakes hoses.
For the brakes everything should bolt on. I’m not sure if the 2 trucks use the same wheel bearings but worst case just swap the spindles too. Don’t forget the brakes hoses.
BC - TEXAS
Registered Member
Parts vehicle. No passenger door, no front clip. Owner says, "engine ran when I bought it, both axles are solid and trans/transfer case are all good.
The '87 is done, but the '70 rocks!!
Yes, the transmission and t-case will bolt up. If you have the driveshafts, they’ll likely bolt right up with the conversion.
You’ll need the 700r4 lockup control. I went with the B&M lockup with the vacuum TCC solenoid cut off. I l had a hard time getting the transmission to unlock following the instructions but I have it all dialed in and it’s great doing the opposite of what the vacuum switch instructions were.
If you go the B&M route, you’ll need a speed sensor off from the transfer case for it. It calls for one of two specific pulses. I have two different ones. One has the cable pass through (for my speedometer) and the other pulse out for the B&M transmission lockup controller.
I had move the crossmember back about 3/4 of an inch. You’ll likely use the crossmember from the donor truck. Drilling the frame for the mounting holes was easy.
Use all all new poly or rubber mounts. Whatever the engine mount is to prevent too little or too much movement.
You’ll need the 700r4 lockup control. I went with the B&M lockup with the vacuum TCC solenoid cut off. I l had a hard time getting the transmission to unlock following the instructions but I have it all dialed in and it’s great doing the opposite of what the vacuum switch instructions were.
If you go the B&M route, you’ll need a speed sensor off from the transfer case for it. It calls for one of two specific pulses. I have two different ones. One has the cable pass through (for my speedometer) and the other pulse out for the B&M transmission lockup controller.
I had move the crossmember back about 3/4 of an inch. You’ll likely use the crossmember from the donor truck. Drilling the frame for the mounting holes was easy.
Use all all new poly or rubber mounts. Whatever the engine mount is to prevent too little or too much movement.
bp71k5
3/4 ton status
The first gens had a different rear axle mount width didn’t they? Or is that just when mounting a 14 bolt in the back?
Watch out for the wheel bearing sizes, the early models had a small bearing and big bearing version. So you may need the spindles if you’re not swapping the whole axle.
Watch out for the wheel bearing sizes, the early models had a small bearing and big bearing version. So you may need the spindles if you’re not swapping the whole axle.
Your information is from putting a 700r4 into a 1st gen originally equipped with a TH350? Because a 700r4 is either 2 1/2 or 3 1/2 inches longer than the TH350, if memory serves.
I did the swap from a TH350 to 700R4, but kept the same transfer case. I did have to move the crossmember back and I had to get new drivelines. Using the donor truck drivelines will save some money.
OK, cool. My main point is that the crossmember will need to move about 3" back (either 2.5" or 3.5"). Considerably more than 3/4".
If the donor driveshafts are in good shape, then yeah, they should bolt right up. However, his original shafts will not.
@BC - TEXAS If you use the donor crossmember, you'll need to ensure that there's no interference with the exhaust routing. Otherwise, you can reuse the original. The tall transfer case adapter should work with both the 700r4 and the TH350.
BC - TEXAS
Registered Member
Guys - Thanks so much! If I'm reading this right, I should be able to do some fairly minor modifications and upgrade my ride. With 35" Nittos, the drum brakes just don't cut it. I also need to 're gear', I guess as it turns a bunch of RPM to hit 60 MPH. I think 410's should make it better, especially with the OD tranny. It'll always be something, but you folks have given me some great info. Anything else you can think of?!!
is the 87 geared at 4.10? I have a 12 bolt rear out of a first gen K5 that is 4.10 (allegedly). or is that what your current axles are? and you are just using from the knuckles out?
(ah I see said the blind man as he picked up his hammer and saw)
edited once the light bulb went off
BC - TEXAS
Registered Member
LOL...I'm thinking I can have the diffs re-geared and have no idea what that should cost. You guys have already been great and have confirmed I can save some money this way. It's always something!!
I do have the rear axle if you are interested. depending on how soon you need it; I could get it to San Antonio
A front and rear regear will run you approx $1000 with the gears. Less if you can do it yourself. That’s why a lot of folks will try to find an axle that’s already got the gear ratio they want.
BC - TEXAS
Registered Member
Thanks!!
