RE: [Chevelle-List] Four Speed to Automatic

[Mark Weber]

I do not know if a TH400 and a manual trans are the same length.  I started with a 400 and went to a 700.   No reputable shop will tell you the size of shaft you need :)  Too risky for them.  They will tell you to measure from yoke center to yoke center and bring them a number.  They can make a shaft the exact length that you specify.   IMO it is not easy getting this measurement.  I took mine while the rear suspension was hanging. I measured three times but somehow when the shaft was put on it is about 1" too short.  Mine will probably work like it is initially, but I intend to have the shop lengthen it or I will get another shaft and have it shortened to the correct length.  My suspension is fully extended yet, with new springs, gas charged shocks, and polygraphite bushings.  If the back end sags or sits down a bit after some use that will locate the drive shaft farther onto the trans output spline.   If you found someone with the transmission setup you want, you could measure the shaft on their car and it would probably be ok.   Good luck.   Mark -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Lojac Sent: Tuesday, March 26, 2002 11:46 AM To: [EMAIL PROTECTED] Subject: Re: [Chevelle-List] Four Speed to Automatic Will I have to shorten the drive shaft with a TH400?  How will I know how much?  Will the machine shop know exactly what to do?   Lojac ----- Original Message ----- From: Mark Weber To: [EMAIL PROTECTED] Sent: Monday, March 25, 2002 10:33 PM Subject: RE: [Chevelle-List] Four Speed to Automatic Lojac, The TH400 and TH700 are different lengths. You will need to shorten the drive shaft if you go to a th700. Not sure of the length, people will tell you to "measure your car".  The trans tunnel on the pass side at the firewall will need to be dented in a bit for clearance with a TH700. Not a big deal but a mod was required on my 1971. The trans cross member needs to move if going from a TH400 to TH700. There were existing holes in my frame I used. It sounds like some frames have correct holes and some people can use one existing hole and drill another on each side. The TH400 trans cooler lines I purchased work on my TH700. If you go from a three speed auto on the floor to a 4 speed, you can change the console face plate and shift detent plate to one for the 4 speed. Year one sells the kits, I think they are about $100.   Mark -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Cecil "Steve" Martin Sent: Monday, March 25, 2002 7:22 PM To: [EMAIL PROTECTED] Subject: RE: [Chevelle-List] Four Speed to Automatic Hey Lojac,                  I am about to convert from Auto-Magic on the column to  “4 on the floor”. Want to swap some parts? It has a TH350 in there right now. I am in Ohio.                                                           Steve   -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Lojac Sent: Sunday, March 24, 2002 10:49 PM To: [EMAIL PROTECTED] Subject: Re: [Chevelle-List] Four Speed to Automatic   Is this an easy swap or complicated?  I have been doing some reading on the web about having to shorten the drive shaft because of the length of the TH400.  Is this true?  I was also wanting to use a TH700....is this any different from doing the swap with the TH400???   Thanks, Lojac