Ive got a 89 305 firebird, the 700r4 lost 3rd n 4th recently so im looking to compile a list of parts to put together a solid th350 or rebuild this 700r4 whichever would be more cost effecient. i know im going to need a corvette servo, 460LE stall correct? this is going to be my first rebuild, ive got a good friend whos done a few th350's whos willing to help, but im wanna get the list of parts togther before hand. Does anyone have parts numbers for shift kits? what other modifications would you suggest and do you think ide be better of finding and pulling a new th350? or just rebuilding this 700r4

 

it all depends on if you want the overdrive or not. the th350 is the same as the 700r4 in third gear but the 700r4 has a .7 overdrive. hard to beat the overdrive for a daily driver or freeway driving.
for the th350 I like the more expensive b&m shift kit, a stock master overhaul kit with all new friction and steels, band, filter, seals, sealing rings, adjustable vacuum modulator, etc. is a must. Also use an aftermarket bolt in center support as the stock one wears out the transmission case. These upgrades should make a bulletproof th350, just make sure to do everything-hot tank it all properly-build it properly-friends are great to save money if they build all the time but will cost you time and money most of the time.
Buy a long th350 so that if you change your mind you could put the 700r4 back in. The long one is the same length as the 700r4 and uses the same driveline.
700r4's are good despite some haters/they just need love that most can't give-like a pimp.

 

Great Great info, now all that considered (i dont mind losing the OD) do you think its going to be more cost effective to buy and rebuild a th350, or just pull and rebuild the 700r4 that ive got now? also i know summits great for the shift kit, but are there any specialty places i should be aware of that deal strictly with tranny parts? i live just 2 secs from a tranny and speed shop, however if its possible ide love to make this a learning experience as well, i hate paying for somthing without even trying myself, and like i said ive got a good friend whos build more then 1 or 2 th350's.

 

TH700-R4s are really no more difficult than a TH350. The TH350 offers no real advantages over the TH700R4. If your case is in good condition, you can buy the parts you would need to refresh the trans for under $160, including all seals, gaskets, clutches, band, separator plate, pump vanes, etc. If you want to make it more robust, you can build a pretty stout trans for under $750, and it will handle a constant 400+ ft/lb and 550 HP with excursions into the 650-ish range on occasion.

Make sure you get a higher RPM, 13-vane pump setup at the least, and a full compliment 3-4 clutch stack. Don't cheap out on the governor, either.

A TCI or TransStar "Beast" reaction sun shell is a must. Beware of the Chinese knock-off "Beast" sun shells, since I've already replaced one of those in one of MY OWN transmissions and a few others in other rebuilds. The Chinese shell in my trans had only about 40K on it when it let go at the spline, and it was behind a 262 V-6, if that tells you anything.

You can install needle thrust bearings in place of the nylon washers to ensure better life at higher RPMs, and less wear.

The school is out as to whether bonded pistons are better than loose seal pistons, and it seems that there is no substantial difference in service life or reliability. When the clutches under a bonded piston wear, the piston sticks. When the clutches under a loose seal piston wear, the seal rolls off, so it's not much different.

You can go nuts and install aftermarket "Torque Drive" input housings and shafts, five-pinion planetary sets, and all manner of other goodies if you want. A 29-roller forward sprag is also a good idea in higher power applications.

You can build either way, and in either case, a new or reman torque converter with a carbon TC clutch is in order. A $200 torque converter to complete the job is good insurance.

 

I disagree. The 700r4 is not a learning transmission. Much more room for error in all areas.
13 vane rotors are different thickness don't do that! If the 700r4 core has a 10 vane that is enough, just install hardened rings to it so they don't shatter at high rpm. There are 13 vane rotors made to fit but most don't realize there is a difference and tears up the whole pump. Typical rookie mistake.
Bearings are bad IMO. I like thrust washers because needle bearings can't come out and circulate through everything. If there are plastic thrusts in some places they can be replaced with brass/yes. If it was designed to have a bearing that is o.k. but why change a proven thrust to a bearing that can do more damage than good.
I know the molded delima all too well. Any line transmission mechanic knows the 3-4 molded piston tends to fail prematurely. Sure it has more apply area but at the expense of longevity. The reason they changed was to make assembly faster IMO.

 

ed o - There are plenty of drop-in 13 vane pump kits which fit into the older 7-10 pump housings. Mixing and matching parts from different series is certainly risky without fully understanding the differences.

You make an excellent point about the Torringtons in the thrust locations. Instead of just wearing, they can lunch the whole box if they fail. They just seem to hold the end play longer than washers (even naval bronze washers).

To me, it's a coin flip whether the bonded/assembled pistons are better. I've seen seals blown off the assembled apply pistons, and more stuck/overextended pistons on the bonded ones. You're probably right on about the easier assembly for the factory people.

 

there is a cool bearing for the rear of the case that takes care of the common failure of the three tab washer spinning in the case. It comes with a new bushing for the rear of the trans housing, a bearing to replace the thrust and tab washer, and shims to set end play. That is what th400's go bad from and it is a great kit to bring them back to life.

 

thanks alot for the great info guys like i said im not going to be attempting this alone and if all else fails, the guys up the street do great work for a great price, that being said where should i start looking for the rebuild kit for the 700r4? and any ides on where to get the beast sun shell? also what differenciats the chineese knock off with the one im lookin for so i make sure i dont buy the wrong one?


edit and any links to parts would be greatly helpfull even if they arnt EXACTLY what im lookin for helping me get an idea on price range per part is gonna help compile the list.

 

Go to https://www.700r4l60e.com/store/prod...&cat=19&page=1 I have been building these for many years now, and I have several different kits for these. The above mentioned is the Strett/Strip rebuild kit. The kit is very complete and has some options. Waht torque converter are you planning on using? Let me know? Dana

 

I like the jet servo v.s. the corvette as it has 35% more hold power than the vette. It also eliminates the spring for third and makes third better along with second/a real easy install as it doesn't require modifying things. . The t.c.i. servo looks the same as the jet if you can't find it.
I'd also get a cover for the servo. It will help hold fourth gear tighter. Superior makes a nice one and uses a lip seal v.s. a sealing ring. holds fourth %40 tighter. Other than that the pro built kit looks good.