I had conversations with my tranny builder in regards to over drive. Here is a copy of the email thread. Some of you may understand it better than I.
Brian 283
Wed, May 9, 2018, 2:22 PM
Hi Steve,
If I wanted to have overdrive on my 65 Pontiac, should I buy a new tranny with overdrive or rebuild my TH400 and add new overdrive unit to existing tranny?
Brian
283 steve@
Wed, May 9, 2018, 6:17 PM
to me
Far superior to go with a 700R4 then doing a TH400 with OD. The problem is overheating and terrible fuel economy, because you do not have a lock up with OD. I’ve seen a lot of people that are angry going the TH400 & OD route.
Do you want to do a TH700R4?
Thanks,
Steve Brian <283>
Wed, May 9, 2018, 6:26 PM
to Steve It's my driver so it would make sense to get overdrive. I have a 3.08 rear end on her. Should we get a core and rebuild one so you can beef it up and put in shift kit and stall? How should we go?
Brian 283
steve@
Thu, May 10, 2018, 1:21 PM
to me
Brian 3.08 x OD gives you a ratio 2.15 which is too low unless you drive at 100mph all the time. A 350 lock up would give you a better combo. How tall are your tires in inches? Brian <283>
Thu, May 10, 2018, 1:32 PM
to Steve Not sure I understand. That normally would have a stock 2.56 or 2.73 rear end diff. 3.08 will have higher rpm at 70mph than 2.56. Idea is to reduce the rpm when we go into OD correct?
15" rims, have not decided on what tire size is. It's a wagon so it won't be too tall.
Brian
283 Brian <283>
Fri, Jan 18, 9:13 AM
to Steve Hi Steve, I would like to figure out weather to go the OD route for my Catalina. My brother-in-law purchased a 65 Pariseenen /wo a tranny. He could take my TH004 and rebuild it. I could get you to rebuild a OD tranny for my Catalina. What would I need to purchase? What is a 350 lockup?
Brian 283 steve@
Mon, Jan 21, 8:46 AM
to me
With 3.08 :: 1 gears in the diff you can’t use OD at all. Your engine rpm at 60 mph would be 1600 rpm. Most gas engines barely make power down that low. You could use the 700 R4 if you change your gears to 3.42, 3.73, 4.11, 4.56, 4.88, 5.12 or 5.30. TH350C are very hard to find. Brian <283>
Mon, Jan 21, 6:58 PM
to Steve Ok, I think I have it now. I have a TriPwr battleship so we go with 200-4R? The 700R4 is for engines /w computer correct? Think I will go with 3.42 or 3.73 gears in the diff. We can use the TH400 you have now for my son-in-law's 65 Pontiac Paris.
Does his make sense?
Brian 283 steve@
Tue, Jan 22, 7:59 AM
to me
No, 700 R4 & 200 4R have almost no computer control. The computer control was for the lock up (TCC) on some models 1985 and up for both transmissions. The 700 R4 has bigger planetaries and can take more abuse.
700 R4 gear ratios:
1st à 3.06 to 1
2nd à 1.62 to 1
3rd à 1 to 1
4th à .69 to 1
200 4R gear ratios:
1st à 2.74 to 1
2nd à 1.57 to 1
3rd à 1 to 1
4th à .71 to 1
If you drive fast, 70 mph & faster, than I would do the 700 R4 & change your gears, other wise stick with the TH400.
Brian 283
to steve
Steve, Let's take the easy route. Rebuild it like the 68 Firebird TH004 you did. Shift kit again. Is there an extra cost to enable the tranny to have a 2400 stall? I realize I need 2400 torque converter but is there anything to add to the tranny rebuild side? Cost? I will let you start anytime you ready. Take your time
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