Hello i am new i am 16 and have a 1990 chevrolet blazer silverado package 4x4. I plan on doing a resto on it and putting a 4" rancho lift in it with 31x12.50r15 bfg all terrains. I am worried about the 700R4 slipping so i was looking into a B&M shift kit to help it but a friend of mine has a 1990 3/4 ton 4x4 and he was talking and said somthing about pulling the valve body in the transmission and it shifting crisper... Would this work? Also will the 350 tbi turn the 31's with no drama and if so will it turn 33's when i buy a set or will i need to regear the axles? Also if in the future i swap in a 400ci sbc will the 700R4 handle it? How much abuse will the 350/700R4/203 combo hold up to mudding and general offtroad abuse?

 

I have an old 4-barrel 350 in my '74 K5 w/ 3.73 gears and it turns 33's just fine.

As far as putting a new valve body in the transmission, I am sure that you could find one that has modified valving, etc, but you can improve the shift firmness yourself with a shift kit and new servos/springs.

 

B&M sells a shift improver kit for about $30-$40 through auto part stores. They are very simple to install even when in the vehicle. Just pull the pan, drain the fluid and read the instructions. remember its a metric fastener transmission, so all you will need is a 10mm and 13mm socket. You will also need a set of snap ring pliers. The kit comes with new springs, blocker stems, and a drill bit thats sized correctly. Depending on what year, you may have to drill 1-2 holes in the plate sandwiched in between the valve body and the trans. Do this to save your butt though... When you pull the valve body off the trans, take a picture and note where the ***** are in the valve body.

After following the directions, fill the trans to just below the full mark. (1/2 qt low) Trust me, it will work better that way. I have spoken to a fellow who has built transmissions for over 40 years and he says that running a transmission just shy of the full mark will make it shift better and run longer than one that's full or overfilled.

 

well it has been decided i may be getting a 6" lift instead of the 4" i planned on buying...also i forgot to post before but this blazer is full time four wheel drive and everyone i told about going with 35" tires told me to go with a tougher tranny like a th350 but will that turn the half ton axles and transfercases into weak links? this will be a daily driver and i have been told to put like 3.50 gears in it? this is just gonna be a trail riding/mud truck/daily driver so it cant be too low geared or too high geared.

 

You will constantly be chasing the "weak link". It comes down to how you drive your vehicle. The 700R4 can be made to be just as strong as the TH350.

If you were close by, I would even swap your 700R4 for a TH350. Heck, I have a TH400 if you are looking for strong.

 

Well i have been doing some work to the blazer and i have questions that are drivetrain and non drivetrain related... I have decided to use the stock 700r for now do to the fact that i need it on the road right now. Being that im a highschool student the only time i have to really do long term work on it is weekends. Also how can you tell when a blazer is too far gone to do a mini resto on? My blazer needs a driver side fender doors hood and two rear fenders and maybe floors is that too much to take on? Being that im doing this peice by peice and i dont really need a hood i am confident i could do it. I also have a worry that when i put 35" tires on it and mud it and do trailriding and such im worried that the 700r is gonna be just like a ticking time bomb... I have been told by many people swap it out but i cant afford to right now but the lift and tires i can.. But as for now the more important question is if this blazer is even worth repairing due to rust? I've been told the exterior is for sure done and im worry about the floors but when i sit in it they dont feel weak i can stomp on the floor and hop into it and it doesnt feel like they are rotted.... This IS MY BIGGEST CONCERN..

 

Answered in your other thread.

 

Well i am going with cut out flares on it so i am thinking when i go with a 6" i will put 37/38" tires on the blazer i know it means going with 1-ton d-train. What would be more ideal? th400 np205 dana 44 fr corp 14-bolt rr? or th350 np205 danna 44 fr cop 14 bolt rr? If i can will i be able to make the half ton transfercase work for me? i want to be able to reuse as many stock parts as possible but still be confident enough to go all out offroad. I am keeping the stock 350ci no matter what dr-train route i go. On that note 383 or built 350? It still needs to retain decent gas mileage so if huge power isnt an option thats fine.

 

LOL You have progressed nicely from 31"s to 38"s. I have run 38"s with a 6" lift on many full size Blazers and Suburbans. 1988 and later fullsizes had a pretty decent 10 bolt rear axle. The axles will live with 38"s if you don't go too nuts with the gas pedal in low range. It also helps to have 3:73s but you probably have 3:42s. I would stay away from 400 small blocks for off road use do to the head gasket problems they can have when getting hot. Who are we kidding here... you will never get "decent" gas mileage with this set up.

 

Well lolz originally i wanted to keep it pretty original looking but and i know this is kinda jumping back and forth but my plans change as i get parts and i have come into some nice center line rims that will bolt onto my stock axles so rather then risking breakage i will stick with 35" tires the reason for this choice is the fact that they are free thus i wont have to buy new rims or run the old stock ones. I am still using cut out 4x flares and will run them untill i decide to fix the fenders and junk. The reason for that is they will be cheaper then full body work and paint. I am hoping the either have a 4" lift or a 6" within the next year or so and hopefully a new set of tires. Depending on how the trans holds up i might swap the 700r for a th350.