It will be a 7.625" rear with the bigger, more even sized spider gears. The 7.5" spider gears are the first to explode. Replace the axle and pinion seals. Obviously the gear oil should be changed and everything inspected.
TH350C Transmission and a Mild 455
- Thread starter 1984Oldsmobile442
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A good trans rebuild is so expensive. You want the best of both worlds but not wasted money. An 8.5 rear end is going to be nearly $1,000 everytime. Keep the 7.625 and just buy the power-trax posi locker or new higher gears from Richmond is a decent cheap brand. The 7.625 is way better than the 7.5 so be happy with what you have. Consider selling the mild 455 and just going with a 350 engine so you can use the transmission you know already works well without having to spend thousands of dollars on a new trans. The T350 is worthless. Chew it up and throw it away, have fun with it. A few years ago I left a 200r4 from an SS at a friends house, then we got into an argument and he moved. Now its gone. Be happy what you have today. I was disappointed to find out the 350 trans was in this 85 I just got, but I'm going to either beat it to death or sell it for like $100. Would rather beat it to death. How far is $100 going to get me towards another 200r4 that I actually want and isnt rusty. Not far
Hey 1984 oldsmobile442, First off, the TH350c will not survive any big block. Second, a TH350 built right can handle one.
For the money, though, You'd be happier with a 200R4. Which can be built to handle your power. Just ask any turbo Buick guy. Some say you have to find the special HP 200R4s to hold real power and that is miss information. The biggest difference is shift points and pressures. All 200R4s can be modified to do that. To mount a 200R4, the only change you would make is to find a trans cross member to mount it. (Too many ways to do this, so just find one and do it.) It uses the same driveshaft and trans mount as a TH350.
You seem interested in learning to rebuild and I feel you on that. Doing it yourself is rewarding. You just need to be able to basically put things back the exact same way you took them apart. That's it!
I remember the first time I did a transmission rebuild in my basement. I had a big table to lay are the parts down in the order they came out. I put the new parts next to the old, then reassembled everything double checking as I went along. I followed a official GM shop service manual a parts guy gave me back then. I like having manuals. But today we got youtube. You are bound to find a bunch of videos that show how to rebuild any trans you want to put in your car. It's not rocket science, but if you don't use patience and the basic abilities, It might as well be rocket science, cause you won't do it right.
As for the rear, Definitely snatch the rear from that Monte you found. Even if it's not a posi, you can put a Powertrax in it and come off on top. As long as you don't put sticky tires on it and hit the track, The rear WILL hold up. With new gears and axles it can handle the track up to about a high 11s. I've seen plenty of high 11 sec and slower cars using the 7.5 and 7.625 with mods. (Welded tubes, racing axles and gears, spools, and lockers) Low 11s and faster is when you reach the physical limits of that rear.
I hope this helps you out.
T
For the money, though, You'd be happier with a 200R4. Which can be built to handle your power. Just ask any turbo Buick guy. Some say you have to find the special HP 200R4s to hold real power and that is miss information. The biggest difference is shift points and pressures. All 200R4s can be modified to do that. To mount a 200R4, the only change you would make is to find a trans cross member to mount it. (Too many ways to do this, so just find one and do it.) It uses the same driveshaft and trans mount as a TH350.
You seem interested in learning to rebuild and I feel you on that. Doing it yourself is rewarding. You just need to be able to basically put things back the exact same way you took them apart. That's it!
I remember the first time I did a transmission rebuild in my basement. I had a big table to lay are the parts down in the order they came out. I put the new parts next to the old, then reassembled everything double checking as I went along. I followed a official GM shop service manual a parts guy gave me back then. I like having manuals. But today we got youtube. You are bound to find a bunch of videos that show how to rebuild any trans you want to put in your car. It's not rocket science, but if you don't use patience and the basic abilities, It might as well be rocket science, cause you won't do it right.
As for the rear, Definitely snatch the rear from that Monte you found. Even if it's not a posi, you can put a Powertrax in it and come off on top. As long as you don't put sticky tires on it and hit the track, The rear WILL hold up. With new gears and axles it can handle the track up to about a high 11s. I've seen plenty of high 11 sec and slower cars using the 7.5 and 7.625 with mods. (Welded tubes, racing axles and gears, spools, and lockers) Low 11s and faster is when you reach the physical limits of that rear.
I hope this helps you out.
T
The 200r4 is way better than either of the 3 speeds, even if guys say 'dont take one from a grandma cutlass' thats a lie it could handle the 455 way better than throwing a 3 speed into the car w/ no rebuild. However, it is nearly impossible to rebuild and in comparison to rebuilding either type of 3 speed the 200r4 looks at least 85% as difficult as rocket science to me idc what anyone says. I bet I could train an ape to rebuild the 3 speed with nothing but a cattle prod and $2.50 worth of bananas from the store. The 200r4 is going to cost you thousands to rebuild w performance mods. Better bet would be to just grab 1 from a car that's on the verge of being crushed and talk the parts yard down. You should expect to pay around $400 for a 200r4 that actually works or its not worth buying so walk away. If the deal is too good to be true it's probably not true. You will not find somebody who will rebuild the 2oor4 for less than $2,000. That's a huge investment, but it would be a better investment than buying an 8.5 rear end that you don't even need at least. If you did what you originally said and put the 3speed behind the 455 but spent more than a grand getting the 8.5 rear in, it wouldn't even be able to push those big *ss gears b/c the 350c is just a little too weak. If you are dead set on the 455 than the 200r4 is the missing piece of the puzzle. The good 350 trans would be fun with a shifter but gets lame with a column shift car really fast; I'm speaking from experience on that one, it is so boring to have only 3 gears without the B&M Shifter and being able to choose gears and being able to downshift is fantastic. Downshift the 350c trans in a bad situation and the surge of torque from the 455 could prove way too high.
http://www.extremeautomatics.com
If you put a 200-4R behind a high performance big block have a shop build it that specializes in hi po 200-4Rs. Plenty of good transmission shops let alone first timers fail at building up a 200-4R to withstand 500+ pounds of torque. The good news is having a quality hi performance 200-4R build isn't as expensive as it used to be. Lonnie has built two for me and I have had good luck with both of them. One behind an 87 442 with a torque monster 509ci Cadillac the other behind my GN. Both ran on drag radials and ran 12.4 @ 109 and 12.5 @ 110 mph. Both ran higher stall lock up converter with 3.42 & 3.73s. Even the 509 pulled off 16.8 & 17.0 mpg on two tanks on an out of state interstate trip.
If you put a 200-4R behind a high performance big block have a shop build it that specializes in hi po 200-4Rs. Plenty of good transmission shops let alone first timers fail at building up a 200-4R to withstand 500+ pounds of torque. The good news is having a quality hi performance 200-4R build isn't as expensive as it used to be. Lonnie has built two for me and I have had good luck with both of them. One behind an 87 442 with a torque monster 509ci Cadillac the other behind my GN. Both ran on drag radials and ran 12.4 @ 109 and 12.5 @ 110 mph. Both ran higher stall lock up converter with 3.42 & 3.73s. Even the 509 pulled off 16.8 & 17.0 mpg on two tanks on an out of state interstate trip.
jetsetw31 said:
Ummm,, I can't recommend rebuilding a 200-4R yourself having personally gone through this with a friend who builds transmissions for a living (primarily FWD trans, TH350's, 400's and 700R4's). We ended up taking the trans out of the car 4 times before getting it right. You need knowledge and experience to build one of these successfully, especially one that can handle any respectable amount of power. Just sayin...
I take pride in doing as much work possible by myself so I understand that aspect and why someone would want to give it a shot. If you enjoy paying more in the long run and the frustrations that come with it then tackle it yourself.
dogshit said:
Don't get me wrong there are plenty of shops that can build a quality 200R4. I've worked with a few and I can say anybody can learn to build this transmission as long as you have the Tools, the instructions (Manuals or videos), quality replacement parts, (Damn near all rebuild kits have the good parts in them now.) and most importantly Attention To Detail (meaning patience and double checking yourself a lot.) My first 200R4 rebuild is still running behind a not stock BBO in a 4000 lb car. (I checked with them last weekend. A 455 in a '83 98 Regency.)
So my statement comes from "If I can do it.... you can too." Follow the manual to the letter and it can be done. The problem is most don't like to do things by the letter.
That's just a fact and It's also good news for the shops.
T
Anubis said:
I too have been through that. And it was my 4th rebuild a 700R4. Wasn't fun at all.
But my point was, If you know you can't do it, don't try and If you think you can, then take your time and double check yourself at every step.
That's what makes the difference (Even in shops) between a quality build and a "Did I need this left over part?".
JMHO
T
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Even asleep dreaming I still pulled up at the shop to have the 200r4 rebuilt instead of going for it - and I have rebuild the TH350 that is why I implied anyone can do the TH350 themself in a well-lit garage with old literature and illustrations on deck it is not hard to figure out. Trying to build a 200r4 as your first trans build, or even your 2nd or 3rd build, would be like someone with no culinary arts degree trying to make a 4-layer wedding cake. It's just not worth the risk of blowing up your at least $400 spent on the 200r4 to risk trying to do it yourself; Part of the reason rebuilds are so expensive is you are also buying a warranty! If a shop isn't willing to even consider offer you a warranty that's a red flag to walk away.
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