TH700R4 Transmission Performance Rebuild 2: Removing the TH700R4 From 1989 Corvette
Must read for getting it benched
This article will help those getting the transmission serviced at a local shop. Including the home re builder. I figured it would be good to go over removal from the vehicle. The bench top rebuild is the cheapest way to get a pro rebuild. The removal and reinstall of the transmission is a labor intensive job but not one that is complex or hard to do. So many of us have the skills to remove a transmission from a car and reinstall it. Now the corvette has got to be the hardest car to remove the TH700R4 from that is why I am using this as an example.
Once out of the car
Once removed from the vehicle the TH700R4 can be serviced by who ever you choose with a significant discount in price of the rebuild project. Many shops that do good work are limited by the amount of cars there shop parking lot can hold. Once they are full they can not take in any more work. That only leaves Bench services.
Benching the Transmission
Many transmission shops will welcome this type of work. Many of them will do this work for all the shops in there local area. But may be apprehensive about warranty on a user installed transmission. So there may be some trade off to look at before moving forward with the bench services of some busy shops. Most shops will welcome a bench top job with open arms. Easy quick work is money for the mechanic and ahop. Since the transmission is already out and ready to be gone over there is no delay on the rebuild process. This allows the techs to make there money that day not a week later when the transmission is installed back in the car and picked up by the customer.
Check the manual
First thing to look at on any job like this is the OEM manual to see if the process is straight forward. I would also run a quick google search just to make sure there is not an easier way to get things done.
The manual calls for J 21366 to hold the torque converter in place as the transmission is removed. This is simply a piece of metal that bolts to the top bell housing bolts and hold the converter from falling out. Very simple design and could easily be made at home or just not needed if you got someone around to help remove the TH700R4 from the car. A tie down or ratchet strap will also do the same job.
Here are a few pictures of the bottom of my car. This C4 corvette has 300K miles so its ruff under here certainly time for some repairs. First picture is of the Exhuast crossover under the tail of the transmission.
The exhaust is removed
You removing the trans its best to hit all the bolts especially the exhaust and the brace bolts with P.B. Blaster or so other rust penetrating fluid to help loosen the bolts. This is really important step on a high mileage car. Pretty much needed on any job of this sort. Best way to make sure you don’t break any bolts in the process. Don’t be surprised if the studs in the exhaust manifold snap off. Old and rusted on for many years its a good chance they will snap much easier than they will come loose.
Removing the C Beam
With the pictures above you can see the first job is to remove the exhaust completely. Since its hung in the back by slip on hangers and held in the front by the engine and a middle connector just behind the cat. Now that the exhaust is out of the way you can remove the trans cooler lines and Tv cable along with the torque converter cover. Now remove the torque converter bolts and bolts to the engine leaving the bottom two in place so you can pull them out later. You will need an 18mm and 21mm wrench to remove the large brace bolts.
Heavy bolts of the C beam best left to large impact
Two in the front and two in the back. Need to remove the exhaust hanger on the brace it will prevent you from getting the brace out once its free. Use a pry bar to lever the transmission over so the brace can be pulled out. Get a large breaker bar and pipe to get the bolts loose on the brace. they are very tight and even after they were broken free they still had to be forced all the way out they never really got loose. The transmission brace has been removed from the transmission. You can pull the drive shaft with a small 8mm wrench. Do your best not to brake a bolt off as you go. The wiring and cables can be removed and two bolts taken out and the transmission removed.
This is the exhaust on the ground.
Here is a picture of the brace its aluminum not that you can tell from this picture. Going to need to clean and paint this one before it goes back in.
Transmission setting on the cart after removal.
Bolts for the transmission brace.
Here is the tail section for the Corvette. You can see this is specific to the Corvette as it has the bolt holes for the brace in the rear.
More to come… I am writing this article as I remove the transmission from my Corvette. Things will be moving at a slow pace.