Original 1969 Riviera with TH400 3 speed. The manual says that L2 and L1 may be used when going down a hill which helps braking the car. Is it okay to use L2 and L1 for take off (race the car) and shift manual to drive or is it not designed for this originally? When i take off part throttle in L2 it shifts stronger/faster between the gears. Thanks.
Upshifting manually isn't an issue, most ppl racing do this anyways. The line pressures get changed when in manual gears
Okay. I don't have an rpm tach installed but i am not pushing it to the limit anyway, just a cruiser. Was wondering how to use the L1 and L2 and using them manually. Good to know it can be used without hurting the trans.
Cruiser? I have a different opinion. I was told a long time ago, by a respected transmission re builder that manually shifting a THM400 can wear it prematurely. He explained that the shifts are accomplished differently when shifting manually vs. automatic (leaving it in Drive). I don't remember the exact specifics. A properly functioning THM400 with a functioning kick down and properly calibrated modulator and governor, will shift where you want it to, all the time. The more throttle you give it, the higher RPM shifts you will get. You can modify that yourself if it doesn't shift where you want it to now.
Dont get me wrong I wouldn't tell someone to do it everywhere they go.......but to use for fun from time to time, or to help control load and speed under certain driving conditions it what it was really ment for
With cruiser i meant that i have never raced my car from L1 or L2, i have no intentions either. What i did the other day is i used L2 from take off part throttle and i felt that it shifts stronger/faster than using drive range. I have no issues with drive range or whatsoever, kick down and all it works just great and it is all i use. I will leave L1 and L2 for what it is. Maybe from time to time a shift at normal or low speed, that's it. Keeping the trans in good shape.
Exactly...i am not gonna do that for sure. Would like to keep engine and trans untouched as long as possible.
Normally a TH400 can free wheel if somehow going down hill with little throttle, pulling it into a lower setting engages on of the 2 bands to allow engine braking (not breaking). That is, the bands are only for deceleration situations or backing up, not high power situations. So there is some difference which you may never notice, I do not believe selecting a lower gear causes more wear than the same power and automatic shifting. I certainly have done it lots. For example I put it in low starting from a turn at a stop sign, then throw on the power when the car is straight. In auto the trans at light throttle would get into a higher gear, then I would need to downshift again when straight to get going. That extra shifting I am sure would do more wear, besides wasting time. As for leaving the trans alone, it would be far better to get it apart and replace the inexpensive soft parts long before now, so they will not die of old age and then cause serious damage to the hard parts. And do replace any original timing chain set. good luck, Bruce Roe
L1 l2 use the bands and consequently the the front planet/reaction carrier. My th400 had a B&m kit that would shift to 3rd by 20 mph with a 2.73 rear, so I was always downshifting. It was evident when apart with the wear on the reaction carrier.
Thanks. I changed breaking to braking. I meant braking ofcourse. The timing set with (nylon) sprocket is still there. No slack. We've replaced a set on another Riviera because of too much slack and far over a 100K miles. Sprocket was just fine. No teeth missing. Timing was all over the place but that was it. Nothing to worry about. Don't know about the trans you mention. Gonna leave it the way it is for now.